Trimble SK8, Lassen-SK8 Reference Manual

Lassen-SK8™ Embedded GPS Module

System Designer Reference Manual

Part Number: 34149-01 Firmware: 7.20-7.52 Date: August 1997

Trimble Navigation Limited Commercial Systems Group 645 North Mary Avenue Post Office Box 3642 Sunnyvale, CA 94088-3642 U.S.A.

+1-800-827-8000 in North America +1-408-481-8000 International FAX: +1-408-730-2082

U.S. Technical Assistance and Repair

+1-800--SOS-4-TAC in North America +1-408-481-6940 International FAX: +1-408-481-6020

European Technical Assistance and Repair

+44-1256-1622-858-421

Copyrights

© 1997 Trimble Navigation Limited. All rights reserved. No part of this manual may be copied, photocopied, reproduced, translated, or reduced to any electronic medium or machine-readable form without prior written consent from Trimble Navigation Limited.

Printed in the United States of America. Printed on recycled paper.

Revision Notice

This is the first release of the Lassen-SK8™ Embedded GPS Module System Designer Reference Manual, Part Number 34149-01, August 1997.

Trademarks

SVeeSix, SVeeSix-CM3, LASSEN-SK8, Acutis, Acutime, AcutimeII, and TSIP are trademarks of Trimble Navigation Limited. IBM is a registered trademark of International Business Machines, Inc. MS-DOS and Windows is a trademark of Microsoft Corporation. Intel is a trademark of Intel Corporation. All other brand names are trademarks of their respective holders.

Disclaimer of Warranty

EXCEPT AS INDICATED IN “LIMITED WARRANTY” HEREIN, TRIMBLE HARDWARE, SOFTWARE, FIRMWARE AND DOCUMENTATION IS PROVIDED “AS IS” AND WITHOUT EXPRESS OR LIMITED WARRANTY OF ANY KIND BY EITHER TRIMBLE OR ANYONE WHO HAS BEEN INVOLVED IN ITS CREATION, PRODUCTION, OR DISTRIBUTION INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK, AS TO THE QUALITY AND PERFORMANCE OF THE TRIMBLE HARDWARE, SOFTWARE, FIRMWARE AND DOCUMENTATION, IS WITH YOU. SOME STATES DO NOT ALLOW THE EXCLUSION OF IMPLIED WARRANTIES, SO THE ABOVE EXCLUSION MAY NOT APPLY TO YOU.

Limitation of Liability

IN NO EVENT WILL TRIMBLE OR ANY PERSON INVOLVED IN THE CREATION, PRODUCTION, OR DISTRIBUTION OF THE TRIMBLE PRODUCT BE LIABLE TO YOU ON ACCOUNT OF ANY CLAIM FOR ANY DAMAGES, INCLUDING ANY LOST PROFITS, LOST SAVINGS, OR OTHER SPECIAL, INCIDENTAL, CONSEQUENTIAL, OR EXEMPLARY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY DAMAGES ASSESSED AGAINST OR PAID BY YOU TO ANY THIRD PARTY, RISING OUT OF THE USE, LIABILITY TO USE, QUALITY OR PERFORMANCE OF SUCH TRIMBLE PRODUCT INCLUDING HARDWARE, SOFTWARE, FIRMWARE, AND DOCUMENTATION, EVEN IF TRIMBLE OR ANY SUCH PERSON OR ENTITY HAS BEEN ADVISED OF THE POSSIBILITY OF DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY. SOME STATES DO NOT ALLOW THE LIMITATION OR EXCLUSION OF LIABILITY FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES SO, THE ABOVE LIMITATIONS MAY NOT APPLY TO YOU.

Software and Firmware Limited Warranty

Trimble warrants that Software and Firmware products will substantially conform to the published specifications provided it is used with the Trimble products, computer products, and operating system for which it was designed. For a period of ninety (90) days, commencing thirty (30) days after shipment from Trimble, Trimble also warrants that the magnetic media on which Software and Firmware are distributed and the documentation are free from defects in materials and workmanship. During the ninety (90) day warranty period, Trimble will replace defective media or documentation, or correct substantial program errors at no charge. If Trimble is unable to replace defective media or documentation, or correct program errors, Trimble will refund the price paid for The Software. These are your sole remedies for any breach in warranty.

Hardware Limited Warranty

Trimble Navigation Limited products are warranted against defects in material and workmanship for a period of one year. The warranty period shall commence thirty (30) days after shipment from Trimble’s factory. Warranty service will be provided at a designated Trimble Service Center. Trimble will at its option either repair or replace products that prove to be defective. The Customer shall pay all shipping charges for products returned to Trimble for warranty service. Trimble shall pay all shipping charges for the return of products to the Customer.

This warranty shall not apply to defects resulting from one or more of the following:

• Improper or inadequate maintenance by the buyer

• Buyer-supplied software or interfacing

• Unauthorized modification or misuse

• Operation outside of the environmental specifications of the product

• Improper installation, where applicable

• Lightning or other electrical discharge

• Fresh or salt water immersion or spray

• Normal wear and tear on consumable parts (for example, batteries)

No other warranty is expressed or implied. Trimble Navigation Limited specifically disclaims the implied warranties of fitness for a particular purpose and merchantability.

Table of Contents

Preface

Scope and Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix

Lassen-SK8 Manual Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

Technical Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

Email. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xx

Worldwide Web . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

Internet FTP Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

FaxBack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

Reader Comment Form. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

Document Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii

Notes, Tips, Cautions, and Warnings. . . . . . . . . . . . . . . . . . . . . . . . . . . xxii

1 Starter Kit

1.1 Lassen-SK8 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

1.1.1 Interface Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Port 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Port 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.1.2 Starter Kit Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.2 GPS Receiver Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

1.3 Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

1.4 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

1.5 Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

1.6 Running the TSIP Interface Program . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

2 Hardware Integration

2.1 The Lassen-SK8 Receiver Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 Interface Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.3 Power Requirement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.4 Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.5 Pulse Per Second . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.6 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.7 RF Shield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Lassen-SK8 Embedded GPS Module v

3 Software Interface

3.1 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.2 Software Tool Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3.3 Communicating with the Lassen-SK8 Module. . . . . . . . . . . . . . . . . . . . . . 3-2

3.4 Protocol Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

3.4.1 TSIP Data Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Configuring the SK 8 receiver output protocol from TSIP to TAIP protocol. 3-4

3.4.2 TAIP Data Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Configuring the SK 8 receiver output protocol from TAIP to TSIP protocol

TAIP message PR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.4.3 NMEA 0183 Data Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3.5 Timing Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.5.1 Effect of GPS Week Number Roll-over (WNRO) . . . . . . . . . . . . . . 3-7

Lassen/Palisade Family Firmware Version 7.xx Software Modifications . . 3-8

3.6 Differential GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

4 Operation and Performance

4.1 GPS Satellite Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.2 Satellite Acquisition and Time to First Fix. . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.2.1 Cold-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.2.2 Warm Start. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.2.3 Garage Search Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.2.4 Hot Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3 Satellite Mask Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

4.3.1 Elevation Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.3.2 SNR Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.3.3 PDOP Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

4.3.4 PDOP Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.4 Standard Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

4.4.1 Fix Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

2D Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

3D Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

2D/3D Automatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.5 Differential GPS Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.5.1 DGPS On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.5.2 DGPS Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.5.3 DGPS Automatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.5.4 Differential GPS Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.6 Position Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

vi Lassen-SK8 Embedded GPS Module

4.6.1 Selective Availability (SA) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.6.2 Differential GPS (DGPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7

4.7 Coordinate Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.7.1 TSIP Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

4.7.2 NMEA 0183 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.7.3 TAIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.8 Performance Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.8.1 Update Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.8.2 Dynamic Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.8.3 Re-Acquisition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

4.9 GPS Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.9.1 Serial Time Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

4.9.2 Timing Pulse Output (PPS) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

4.10 System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

A Trimble Standard Interface Protocol

A.1 Interface Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

A.2 Automatic Output Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2

A.3 Customizing Receiver Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

A.3.1 TAIP Customizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

A.3.2 NMEA Customizing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

A.3.3 Reconfiguring to Factory Default Settings . . . . . . . . . . . . . . . . . . A-3

A.4 Automatic Position and Velocity Reports . . . . . . . . . . . . . . . . . . . . . . . . A-5

A.5 Warm Start Packets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6

A.6 Packets Output at Power-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-7

A.7 Differential GPS Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-7

A.8 Timing Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8

A.9 Satellite Data Packets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8

A.10 Background Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8

A.11 Backwards Incompatibility of Lassen-SK8 Packets with Previous TSIP Versions . . . A-9

A.12 Recommended TSIP Packets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-11

A.13 Command Packets Sent to the Receiver . . . . . . . . . . . . . . . . . . . . . . . . . A-13

A.14 Report Packets Sent by the GPS Receiver to the User . . . . . . . . . . . . . . . . . . A-15

A.15 Key Setup Parameters or Packet BB . . . . . . . . . . . . . . . . . . . . . . . . . . . A-16

A.15.1 Packet 0xBB - Set Fix Mode . . . . . . . . . . . . . . . . . . . . . . . . . A-17

A.15.2 Dynamics Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-17

A.15.3 Elevation Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-17

A.15.4 Signal Level Mask. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-18

A.15.5 DOP Mask and Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-18

Lassen-SK8 Embedded GPS Module vii

A.15.6 Packet 0xBB - Set DGPS Mode . . . . . . . . . . . . . . . . . . . . . . . . A-19

A.16 Packet Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-19

A.17 Packet Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

A.17.1 Command Packet 0x1D . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

A.17.2 Command Packet 0x1E . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

A.17.3 Command Packet 0x1F . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

A.17.4 Command Packet 0x21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

A.17.5 Command Packet 0x23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.6 Command Packet 0x24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.7 Command Packet 0x25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.8 Command Packet 0x26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.9 Command Packet 0x27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.10 Command Packet 0x28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

A.17.11 Command Packet 0x2A . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-22

A.17.12 Command Packet 0x2B . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-23

A.17.13 Command Packet 0x2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-23

A.17.14 Command Packet 0x2E . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-23

A.17.15 Command Packet 0x31 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-24

A.17.16 Command Packet 0x32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-24

A.17.17 Command Packet 0x35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-24

A.17.18 Command Packet 0x37 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-26

A.17.19 Command Packet 0x38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-27

A.17.20 Command Packet 0x39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-28

A.17.21 Command Packet 0x3C . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-28

A.17.22 Report Packet 0x41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-29

A.17.23 Report Packet 0x42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

A.17.24 Report Packet 0x43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

A.17.25 Report Packet 0x45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-31

A.17.26 Report Packet 0x46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-32

A.17.27 Report Packet 0x47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-33

A.17.28 Report Packet 0x48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-33

A.17.29 Report Packet 0x4A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-33

A.17.30 Main 0x4A Report Packet Type. . . . . . . . . . . . . . . . . . . . . . . . A-34

A.17.31 Second 0x4A Packet Type. . . . . . . . . . . . . . . . . . . . . . . . . . . A-34

Reference Altitude. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-34

Altitude Flag. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-35

A.17.32 Report Packet 0x4B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-35

A.17.33 Report Packet 0x4D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-36

A.17.34 Report Packet 0x4E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-36

viii Lassen-SK8 Embedded GPS Module

A.17.35 Report Packet 0x55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-37

A.17.36 Report Packet 0x56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-39

A.17.37 Report Packet 0x57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-39

A.17.38 Report Packet 0x58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-40

A.17.39 Report Packet 0x59 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-44

A.17.40 Report Packet 0x5A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-45

A.17.41 Report Packet 0x5C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-47

A.17.42 Command Packet 0x60 -. . . . . . . . . . . . . . . . . . . . . . . . . . . . Type

1 Differential GPS CorrectionsA-48

A.17.43 Command Packet 0x61 -. . . . . . . . . . . . . . . . . . . . . . . . . . . . Set

Differential GPS CorrectionsA-49

A.17.44 Command Packet 0x62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-49

A.17.45 Command Packet 0x65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-50

A.17.46 Report Packet 0x6D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-50

A.17.47 Command Packet 0x6E — Set or Request Synchronized

Measurement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . A-51

Enable / Disable Synchronized Measurements . . . . . . . . . . . . . . . . A-51

Output Level. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-51

A.17.48 Report Packet 0x6E — Synchronized Measurements. . . . . . . . . . . . . A-52

A.17.49 Report Packet 0x6F, Subcode 1 . . . . . . . . . . . . . . . . . . . . . . . . A-52

A.17.50 Command Packet 0x70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-54

A.17.51 Report 0x70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-54

A.17.52 Command Packet 0x7A . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-55

A.17.53 Report Packet 0x7B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-56

A.17.54 Report Packet 0x82 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-56

A.17.55 Report Packet 0x83 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-57

A.17.56 Report Packet 0x84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-57

A.17.57 Report Packet 0x85 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-58

A.17.58 Packets 0x8E and 0x8F . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-58

A.17.59 Command Packet 0xBB. . . . . . . . . . . . . . . . . . . . . . . . . . . . A-59

A.17.60 Report Packet 0xBB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-60

A.17.61 Command Packet 0xBC. . . . . . . . . . . . . . . . . . . . . . . . . . . . A-60

A.17.62 Report Packet 0xBC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-61

A.18 TSIP Superpackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-62

A.18.1 Command Packet 0x8E-15 - Set/Request Datum . . . . . . . . . . . . . . . A-62

A.18.2 Command Packet 0x8E-19 . . . . . . . . . . . . . . . . . . . . . . . . . . A-64

A.18.3 Command Packet 0x8E-20 . . . . . . . . . . . . . . . . . . . . . . . . . . A-64

A.18.4 Command Packet 0x8E-26 . . . . . . . . . . . . . . . . . . . . . . . . . . A-65

A.18.5 Report Packet 0x8F-15 - Current Datum Values . . . . . . . . . . . . . . . A-65

A.18.6 Report Packet 0x8F-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-66

Lassen-SK8 Embedded GPS Module ix

A.18.7 Report Packet 0x8F-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-66

A.18.8 Report Packet 0x8F-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-67

A.18.9 Report Packet 0x8F-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-67

A.18.10 Report Packet 0x8F-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-69

A.19 Datums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-70

A.20 Reference Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-75

B TSIP User's Guide C Trimble ASCII Interface Protocol (TAIP)

C.1 Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

C.1.1 Start of a New Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

C.1.2 Message Qualifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

C.1.3 Message Identifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.1.4 Data String. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.1.5 Vehicle ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.1.6 Checksum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.1.7 Message Delimiter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

C.2 Sample PV Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-4

C.3 Time and Distance Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

C.4 Latitude and Longitude Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

C.5 Message Data Strings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

C.23 Communication Using TAIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-27

C.23.1 Query for Single Sentence. . . . . . . . . . . . . . . . . . . . . . . . . . . C-27

C.23.2 The Response to Query or Scheduled Report . . . . . . . . . . . . . . . . . C-27

C.23.3 The Set Qualifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-28

C.23.4 Sample Communication Session . . . . . . . . . . . . . . . . . . . . . . . C-28

D GPSSK User's Guide (TAIP)

D.1 The GPSSK Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1

D.2 TAIP.C Source File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2

D.3 GPSSK Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2

D.4 On-line Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-2

D.5 Connecting the GPS Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-3

E NMEA 0183

E.1 The NMEA 0183 Communication Interface . . . . . . . . . . . . . . . . . . . . . . . E-1

E.2 NMEA 0183 Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2

E.3 NMEA 0183 Message Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-2

x Lassen-SK8 Embedded GPS Module

E.4 NMEA 0183 Message Formats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3

E.4.1 GGA - GPS Fix Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3

E.4.2 GLL - Geographic Position - Latitude/Longitude. . . . . . . . . . . . . . . E-4

E.4.3 GSA - GPS DOP and Active Satellites . . . . . . . . . . . . . . . . . . . . E-4

E.4.4 GSV - GPS Satellites in View. . . . . . . . . . . . . . . . . . . . . . . . . E-5

E.4.5 RMC - Recommended Minimum Specific GPS/Transit Data. . . . . . . . . E-6

E.4.6 VTG - Track Made Good and Ground Speed . . . . . . . . . . . . . . . . . E-6

E.4.7 ZDA - Time & Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-7

F Specifications and Mechanical Drawings

F.1 GPS Receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

F.1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

F.1.2 Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

F.1.3 DGPS Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

F.1.4 Datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-1

F.1.5 Acquisition Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.1.6 Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.2 Environmental Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.2.1 Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.2.2 Vibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.2.3 Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.2.4 Humidity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-2

F.3 Physical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.3.1 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.3.2 Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.3.3 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.4 Input/Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.4.1 Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.4.2 Protocols Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-3

F.5 Pulse Per Second . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.5.1 Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.5.2 Pulse Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.5.3 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.6 RF Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.6.1 Jamming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.6.2 Burnout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-4

F.7 Lassen-SK8 Crystal Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . F-5

F.7.1 Electrical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-5

F.7.2 Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-5

Lassen-SK8 Embedded GPS Module xi

F.7.3 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F-5

Glossary Index

xii Lassen-SK8 Embedded GPS Module

List of Figures

Figure 1-1. The Module Installed Inside the Interface Unit . . . . . . . . . . . . . . . . . . . 1-5

Figure 1-2. Receiver Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Figure 1-3. Starter Kit Interface Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Figure 1-4. Open Collector PPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Figure 1-5. Magnetic Mount GPS Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

Figure 1-6. Hard Mount GPS Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

Figure 1-7. Bullet II GPS Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

Figure 1-8. DC Power Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

Figure 1-9. AC/DC Power Converter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

Figure 1-10. Interconnect Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

Figure 1-11. TSIPCHAT Command Window and Report Window . . . . . . . . . . . . . . . . 1-12

Figure 2-1. Motherboard Connection Points . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Figure 2-2. Removing the Receiver Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Figure 2-3. Interface Connector Pin Identification . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Figure 4-1. Lassen-SK8 Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

Figure F-1. Lassen-SK8 Mechanical Drawing - Circuit Board and Shield. . . . . . . . . . . . F-6

Figure F-2. Lassen-SK8 Mechanical Drawing - Motherboard Schematic . . . . . . . . . . . . F-7

Figure F-3. Lassen-SK8 Mechanical Drawing - Miniature Antenna . . . . . . . . . . . . . . . F-8

Figure F-4. Lassen-SK8 Mechanical Drawing - Trimble Bulkhead Antenna . . . . . . . . . . F-9

Figure F-5. Lassen-SK8 Mechanical Drawing - Bullet II Antenna . . . . . . . . . . . . . . . . F-10

Lassen-SK8 Embedded GPS Module xiii

xiv Lassen-SK8 Embedded GPS Module

List of Tables

Table 1-1. Lassen-SK8 Starter Kit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Table 1-2. Lassen-SK8 Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Table 1-3. Lassen SK-8 Optional Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Table 2-1. I/O Connector Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Table 2-2. Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Table 3-1. Default Serial Port Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Table 3-2. TSIP Message Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Table 4-1. Default Satellite Mask Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Table 4-2. Lassen-SK8 Operating Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9

Table A-1. Automatic Output Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2

Table A-2. Customizing Receiver Operation I/Os . . . . . . . . . . . . . . . . . . . . . . . . A-4

Table A-3. Automatic Position and Velocity Reports Control Setting Bits . . . . . . . . . . . A-5

Table A-4. Warm Start Packet Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6

Table A-5. Packet Power-up Output Messages. . . . . . . . . . . . . . . . . . . . . . . . . . A-7

Table A-6. Differential GPS Packet TSIP Control Commands . . . . . . . . . . . . . . . . . A-7

Table A-7. Timing Packet TSIP Control Commands . . . . . . . . . . . . . . . . . . . . . . A-8

Table A-8. Satellite Date Packet Data I/O Descriptions . . . . . . . . . . . . . . . . . . . . . A-8

Table A-9. Background Packet Output Messages . . . . . . . . . . . . . . . . . . . . . . . . A-8

Table A-10. Supported Auto-Output Packet Command Backward Compatibility . . . . . . . . A-9

Table A-11. TSIP Command Backward Incompatibility . . . . . . . . . . . . . . . . . . . . . A-10

Table A-12. Recommended TSIP Packet Data . . . . . . . . . . . . . . . . . . . . . . . . . . A-11

Table A-13. User-Selected Command Packet Options . . . . . . . . . . . . . . . . . . . . . . A-13

Table A-14. User-Selected Report Packet Options . . . . . . . . . . . . . . . . . . . . . . . . A-15

Table A-15. Setup Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-16

Table A-16. Command Packet 0x1E Format . . . . . . . . . . . . . . . . . . . . . . . . . . . A-20

Table A-17 Command Packet 0x23 Data Format. . . . . . . . . . . . . . . . . . . . . . . . . A-21

Table A-18. Packet 0x2A Set Altitude Only Description . . . . . . . . . . . . . . . . . . . . . A-22

Table A-19. Reset Altitude Flag Description . . . . . . . . . . . . . . . . . . . . . . . . . . . A-22

Table A-20. Command Packet 0x23 Data Format. . . . . . . . . . . . . . . . . . . . . . . . . A-23

Table A-21. Command Packet 0x2E Data Formats . . . . . . . . . . . . . . . . . . . . . . . . A-23

Table A-22. Command Packets 0x35 and 0x55 Data Descriptions . . . . . . . . . . . . . . . . A-25

Table A-23. Command Packet 0x38 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . A-27

Lassen-SK8 Embedded GPS Module xv

Table A-24. Command Packet 0x39 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . A-28

Table A-25. Command Packet 0x3C Data Format. . . . . . . . . . . . . . . . . . . . . . . . . A-28

Table A-26. Report Packet 0x41 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-29

Table A-27. Packets 0x41 and 0x46 Status Code Relationships. . . . . . . . . . . . . . . . . . A-29

Table A-28. Report Packet 0x42 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

Table A-29. Report Packet 0x43 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

Table A-30. Report Packet 0x45 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-31

Table A-31. Report Packet 0x46 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-32

Table A-32. Report Packet 0x46 Bit Positions and Descriptions . . . . . . . . . . . . . . . . . A-32

Table A-33. Report Packet 0x47 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-33

Table A-34. Report Packet 0x4A Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-34

Table A-35. Reference Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-35

Table A-36. Report Packet 0x4B Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-35

Table A-37. Report Packet 0x4B Bit Positions and Descriptions . . . . . . . . . . . . . . . . . A-35

Table A-38. Report Packet 0x4E Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-36

Table A-39. Command Packets 0x55 and 0x35 Data Descriptions . . . . . . . . . . . . . . . . A-37

Table A-40. Report Packet 0x56 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-39

Table A-41. Report Packet 0x57 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-39

Table A-42. Report Packet 0x58 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-40

Table A-43. Report Packet 0x58 Almanac Data . . . . . . . . . . . . . . . . . . . . . . . . . . A-41

Table A-44. Report Packet 0x58 Almanac Health Data . . . . . . . . . . . . . . . . . . . . . . A-41

Table A-45. Report Packet 0x58 Ionosphere Data. . . . . . . . . . . . . . . . . . . . . . . . . A-42

Table A-46. Report Packet 0x58 UTC Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-42

Table A-47. Report Packet 0x58 Ephemeris Data . . . . . . . . . . . . . . . . . . . . . . . . . A-42

Table A-48. Report Packet 0x59 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-44

Table A-49. Report Packet 0x5A Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-45

Table A-50. Report Packet 0x5C Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-47

Table A-51. Report Packet 0x60 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-48

Table A-52. Report Packet 0x60 Data Formats for Health and Power . . . . . . . . . . . . . . A-48

Table A-53. Command Packet 0x61 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . A-49

Table A-54. Report Packet 0x6D Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-50

Table A-55. Set Synchronized Measurement Parameters . . . . . . . . . . . . . . . . . . . . . A-51

Table A-56. Request Synchronized Measurement Parameters . . . . . . . . . . . . . . . . . . A-51

Table A-57. Set Synchronized Measurement Parameters . . . . . . . . . . . . . . . . . . . . . A-52

Table A-58 Synchronized Measurements Report . . . . . . . . . . . . . . . . . . . . . . . . . A-52

Table A-59 FLAGS1 Bit Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-53

Table A-60. Command and Report Packet 0x70 Field Descriptions . . . . . . . . . . . . . . . A-54

Table A-61. Command Packet 0x7A Data Formats . . . . . . . . . . . . . . . . . . . . . . . . A-55

xvi Lassen-SK8 Embedded GPS Module

Table A-62. Command Packet 0x7A Data Formats for Setting NMEA Interval and Message MaskA55

Table A-63. Report Packet 0x7B Message Mask Settings . . . . . . . . . . . . . . . . . . . . A-56

Table A-64. Report Packet 0x83 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-57

Table A-65. Report Packet 0x84 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-57

Table A-66. Report Packet 0x85 Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . A-58

Table A-67. Report Packet 0x85 Summary Status Code Encoding . . . . . . . . . . . . . . . . A-58

Table A-68. Command Packet 0xBB Query Mode Data Format . . . . . . . . . . . . . . . . . A-59

Table A-69. Command and Report Packet 0xBB Field Descriptions . . . . . . . . . . . . . . . A-59

Table A-70. Command Packet 0xBC Port Characteristics Query Field Descriptions. . . . . . . A-60

Table A-71. Command Packet 0xBC Field Descriptions . . . . . . . . . . . . . . . . . . . . . A-60

Table A-72. Report Packet 0xBC Field Descriptions . . . . . . . . . . . . . . . . . . . . . . . A-61

Table A-73. Command Packet 0x8E-15 Field Descriptions. . . . . . . . . . . . . . . . . . . . A-63

Table A-74. Command Packet 0x8E-15 Datum Index Field Descriptions . . . . . . . . . . . . A-63

Table A-75. Command Packet 0x8E-15 Eccentricity of the Ellipse Parameter Field Descriptions A-63

Table A-76. Command Packet 0x8E-19Field Description . . . . . . . . . . . . . . . . . . . . A-64

Table A-77. Command Packet 0x8E-20 Field Descriptions. . . . . . . . . . . . . . . . . . . . A-64

Table A-78. Command Packet 0x8E-26 Definitions . . . . . . . . . . . . . . . . . . . . . . . A-65

Table A-79. Report Packet 0x8F-15 Field Descriptions for Converting Ellipsoid

ECFF XYZ to Coordinate System LLA . . . . . . . . . . . . . . . . . . . . . . . A-65

Table A-80. Report Packet 0x8F-17 Field Descriptions. . . . . . . . . . . . . . . . . . . . . . A-66

Table A-81. Report Packet 8F-18 Field Descriptions . . . . . . . . . . . . . . . . . . . . . . . A-67

Table A-82. Command Packet 0x8F-19 Field Descriptions . . . . . . . . . . . . . . . . . . . . A-67

Table A-83. Report Packet 0x8F-20 Data formats. . . . . . . . . . . . . . . . . . . . . . . . . A-67

Table A-84. Report Packet 0x8F-20 Fix SVs . . . . . . . . . . . . . . . . . . . . . . . . . . . A-69

Table A-85. Report Packet 0x8F-26 Field Descriptions. . . . . . . . . . . . . . . . . . . . . . A-69

Table A-86. Datums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-70

Table C-1. Message Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

Table C-2 Message Format Qualifiers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2

Table C-3. Time and Distance Reporting Message Format Qualifiers. . . . . . . . . . . . . . C-4

Table C-4. Time and Distance Reporting Message Format Qualifiers. . . . . . . . . . . . . . C-5

Table C-5. Message Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

Table C-6. Altitude/Up Velocity Data String Descriptions . . . . . . . . . . . . . . . . . . . C-8

Table C-7. Auxiliary Port Characteristics Data String Descriptions. . . . . . . . . . . . . . . C-9

Table C-8. Compact Position Solutions Data String Descriptions . . . . . . . . . . . . . . . . C-10

Table C-9. RTCM-104 Record Types 1 and 9 Data String Descriptions . . . . . . . . . . . . C-11

Table C-10. Delta Differential Corrections Data String Descriptions. . . . . . . . . . . . . . . C-12

Table C-11. Delta Differential Corrections Data String Descriptions. . . . . . . . . . . . . . . C-13

Table C-12. Identification Number Data String Descriptions . . . . . . . . . . . . . . . . . . . C-14

Table C-13. Initial Position Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . . C-15

Lassen-SK8 Embedded GPS Module xvii

Table C-14. Long Navigation Message Data String Descriptions. . . . . . . . . . . . . . . . . C-16

Table C-15. PR Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-17

Table C-16. Port Characteristic Data String Descriptions . . . . . . . . . . . . . . . . . . . . . C-18

Table C-17. Position/Velocity Solution Data String Descriptions. . . . . . . . . . . . . . . . . C-19

Table C-18. IReporting Mode Data String Descriptions. . . . . . . . . . . . . . . . . . . . . . C-20

Table C-19. Reset Mode Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . . . C-21

Table C-20. IData String Hex Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-22

Table C-21. Tracking Status Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-22

Table C-22. Error Codes: Nibble 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-23

Table C-23. Error codes: Nibble 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-23

Table C-24. Error Codes – Nibble 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-24

Table C-25. TM Time/Data Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . . C-25

Table C-26. Version Number Data String Descriptions . . . . . . . . . . . . . . . . . . . . . . C-26

Table E-1. NMEA 0183 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1

Table E-2. Lassen-SK8 NMEA Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-3

Table E-3. GGA - GPS Fix Data Message Parameters. . . . . . . . . . . . . . . . . . . . . . E-3

Table E-4. GLL - Geographic Position - Latitude / Longitude Message Parameters . . . . . . E-4

Table E-5. GSA - GPS DOP and Active Satellites Message Parameters . . . . . . . . . . . . E-4

Table E-6. GSV - GPS Satellites in View Message Parameters . . . . . . . . . . . . . . . . . E-5

Table E-7. RMC - Recommended Minimum Specific GPS / Transit Data Message Parameters E-6

Table E-8. VTG - Track Made Good and Ground Speed Message Parameters . . . . . . . . . E-6

Table E-9. ZDA - Time & Date Message Parameters . . . . . . . . . . . . . . . . . . . . . . E-7

xviii Lassen-SK8 Embedded GPS Module

Preface

The Global Positioning System (GPS) is a satellite based navigation system operated and maintained by the U.S. Department of Defense. The GPS consists of a constellation of 24 satellites providing world-wide, 24 hour, three dimensional (3-D) coverage. Although originally conceived for military needs, GPS has a broad array of civilian applications including surveying, marine, land, aviation, and vehicle navigation. GPS is the most accurate technology available for vehicle navigation.

As a satellite based system, GPS is immune to the limitations of land based systems such as Loran. Loran navigation is limited in coverage and is encumbered by adverse weather. In addition, the accuracy of Loran navigation varies with geographic location and, even under ideal conditions, cannot compare with GPS. By computing the distance to GPS satellites orbiting the earth, a GPS receiver can calculate an accurate position. This process is called satellite ranging. A 2-D position calculation requires three satellite ranges. A 3-D position calculation, which includes altitude, requires four satellite ranges. GPS receivers can also provide precise time, speed, and course measurements which are beneficial for vehicle navigation.

Differential GPS (DGPS) is a sophisticated form of GPS navigation which provides even greater positioning accuracy. Differential GPS relies on error corrections transmitted from a GPS receiver placed at a known location. This receiver, called a reference station, calculates the error in the satellite range data and outputs corrections for use by other GPS receivers. These GPS receivers are designated as mobile units and can be dispersed as far as 100 Km from the base station. Differential GPS eliminates virtually all the measurement error in the satellite ranges and enables a highly accurate position calculation. The Lassen-SK8 is differential-ready for applications requiring DGPS accuracy.

Scope and Audience

Even if you have used other Global Positioning System (GPS) receivers, we recommend that you spend some time reading this manual. The following section provides you with a guide to this manual, as well as to other documentation included with this product.

Lassen-SK8 Embedded GPS Module xix

Preface

Lassen-SK8 Manual Organization

All of the information required to integrate and operate theLassen-SK8 is contained in this Manual. This manual contains the following chapters and appendices:

Chapter 1: Starter Kit Chapter 2: Hardware Integration Chapter 3: Software Interface Chapter 4: Operation and Performance Appendix A:Trimble Standard Interface Protocol Appendix B:TSIP User's Guide Appendix C:Trimble ASCII Interface Protocol (TAIP) Appendix D:GPSSK User's Guide (TAIP) Appendix E:NMEA 0183 Appendix F:Specifications and Mechanical Drawings Glossary The Lassen-SK8 is easy to integrate and simple to use. Before proceeding with Chapter 1,

please review the information contained in this Preface for an overview of the Global Positioning System.

Technical Assistance

If you have problems and cannot find the information you need in this document, call the Trimble Technical Assistance Center (TAC). The phone numbers are:

You can call the Technical Assistance Center phones between 6 AM (0600) to 5:30 PM (1730) Pacific Standard Time. A support technician will take your call, help you determine the source of your problem, and provide you with any technical assistance you might need.

You can send email to the Technical Assistance Center at any time. Asupport technician will respond to your email questions or comments. The email address is:

+1-800-SOS-4TAC (North America) +1-408-481-6940 (International) +1-408-481-6020 (FAX)

xx Lassen-SK8 Embedded GPS Module

trimble_support@trimble.com.

Worldwide Web

Check the Trimble worldwide web site on the Internet (http://www.trimble.com) for the latest news on new products and releases.

Internet FTP Address

You can visit the Trimble Public FTP site at any time to access software patches, utilities, service bulletins, and FAQs. The FTP site address is:

ftp.trimble.com/pub/sct/embeded/bin.

FaxBack

FaxBack is a completely automated fax response system for selecting documents and catalogs (lists of available documents) to be faxed back to a fax machine. Call from a tonedialing phone and FaxBack guides you through the call by playing a pre-recorded voice message.

The FaxBack system is available 24 hours a day, seven days a week. You can order a variety of documents, including; data sheets, application notes, technical documentation, configuration guides, assembly drawings, and general information.

Preface

To call the FaxBack service, dial the following number and follow the instructions:

+1-408-481-7704

Reader Comment Form

A reader comment form is provided at the end of this guide. If this form is not available, comments and suggestions can be sent to:

Trimble Navigation Limited 645 North Mary Avenue Post Office Box 3642, Sunnyvale, CA 94088-3642

All comments and suggestions become the property of Trimble Navigation Limited.

Lassen-SK8 Embedded GPS Module xxi

Preface

Document Conventions

Italics Software menus, menu commands, dialog boxes and fields.

SMALL CAPITALS DOS commands, directories, filenames, and filename extensions.

Courier Represents what is printed on the computer screen.

Courier Bold Information that to be typed in a software screen or window.

[Return] or [Ctrl] + [C] Identifies a hardware function key or key combination that must be pressed on

a computer keyboard.

Helvetica Bold represents a software command button.

Notes, Tips, Cautions, and Warnings

Notes, tips, cautions, and warnings are used to emphasize important information.

Note – Notes give additional significant information about the subject to increase your knowledge, or guide your actions. A note can precede or follow the text it references.

Tip – Indicates a shortcut or other time or labor-saving hint that can help you make better use of the product.

Caution – Cautions alert you to situations that could cause hardware damage or software error. A caution precedes the text it references.

Warning – Warnings alert you to situations that could cause personal injury or unrecoverable data loss. A warning precedes the text it references.

xxii Lassen-SK8 Embedded GPS Module

1 Starter Kit

The Lassen-SK8, based on SierraTM GPS technology, delivers an unmatched level of performance for embedded GPS applications. Sierra technology is Trimble's 8-channel GPS architecture based on two ASICs, the Scott RF ASIC and the Scorpion DSP.

The Scott RF ASIC features:

• Double down-conversion process

• Higher sensitivity

• Lowest power consumption

The double down-conversion process improves immunity to in-band jammers. The system provides a higher sensitivity which allows Lassen-SK8 to track weak satellites and improves position availability in environments with obscured coverage.

The Scorpion ASIC provides the following features in a single package:

• Integrates an 8-channel DSP with 4 correlators per channel

• 32-bit microprocessor

• Real-time clock

• DUART

The 8-channel, 32-correlator design provides extremely fast cold starts while delivering 2 meter DGPS performance. The high level of integration provides a small footprint (3.25" x 1.25" x 0.40") and contributes to the lowest power consumption (.75 watts) for a complete GPS receiver. The combination of small size and low power consumption allows Lassen-SK8 to be embedded in small battery operated devices and in devices where heat dissipation must be minimized.

The Starter Kit makes it simple to evaluate the Lassen-SK8 module's exceptional performance. The kit includes the following:

• Lassen-SK8 receiver installed inside an interface unit

• Magnetic mount antenna

• AC power adapter

• Serial interface cable

• GPS Tool Kit Software used to communicate with the GPS module

Lassen-SK8 Embedded GPS Module 1-1

Starter Kit

The interface unit is a sturdy metal enclosure containing an interface motherboard. The motherboard accepts 9 - 32 VDC power and provides regulated +5V and +3.6V BBU power to the Lassen-SK8 receiver module. The motherboard also provides two RS-232 connectors for quick and direct connection to a PC COM port. The Lassen-SK8 board can be removed from the motherboard for integration into the user's application (see Chapter 2, Hardware Integration).

1.1 Lassen-SK8 Overview

The Lassen-SK8 is a complete 8-channel parallel tracking GPS receiver designed to operate with the L1 frequency, Standard Position Service, Coarse Acquisition code. Using two highly integrated Trimble custom integrated circuits, the receiver is designed in a modular format especially suited for embedded applications. The Lassen-SK8 features Trimble's latest signal processing code, a high-gain RF section for compatibility with standard 25 dB active gain GPS antennas, and a CMOS TTL level pulse-per-second (PPS) output for timing applications or as a general purpose synchronization signal

The Lassen-SK8 acquires a position fix with minimal delay after power cycling. The information necessary to help track satellites is stored in RAM using backup power for the following:

• Almanac

• Ephemeris

• Real-time clock

• Last position

User settings, including port parameters and receiver processing options, are stored in a non-volatile electrically erasable ROM (EEROM) that does not require backup power.

The Lassen-SK8 has two independently configurable serial I/O communication ports. Port1 is a bi-directional control and data port utilizing the Trimble Standard Interface Protocol (TSIP) or Trimble ASCII interface protocol TAIP. Port 2 is a bi-directional port used to receive differential GPS (DGPS) corrections in industry standard RTCMSC-104 format and for output of industry standard ASCII NMEA sentences. The dual data I/O port characteristics and other options are user programmable and stored in non-volatile memory.

Warning – When customizing port assignments or characteristics, confirm that your changes do not effect your ability to communicate with the receiver module (see Chapter 3, Software Interface).

1-2 Lassen-SK8 Embedded GPS Module

1.1.1 Interface Protocols

The Lassen-SK8 operates using either of three protocols — Trimble Standard Interface Protocol (TSIP), Trimble ASCII Interface Protocol (TAIP), and NMEA 0183 and are physically located at the following ports:

• Port 1 TSIP or TAIP

• Port 2 NMEA 0183

Port 1

TSIP is a powerful binary packet protocol that allows the system designer maximum configuration control over the GPS receiver for optimum performance in any number of applications. TSIP supports over 40 commands and their associated response packets for use in configuring the Lassen-SK8 receiver module to meet user requirements.

TAIP is designed for easy integration using programmable ASCII characters in the form of 2-character message types which provide position.

Port 2

NMEA 0183 is an industry standard protocol common to marine applications. NMEA provides direct compatibility with other NMEA-capable devices such as chart plotters, radars, etc. The Lassen-SK8 receiver module supports most NMEA messages for GPS navigation. NMEA messages and output rates can be user selected as required. RTCM SC104 is the GPS industry standard for differential correction data. The receive side of port 2 is configured to accept RTCM data.

Starter Kit

1.1.2 Starter Kit Components

The Lassen-SK8 is available in a developer's Starter Kit or as individual boards. The Starter Kit includes all the components necessary to quickly test and integrate the module.

Lassen-SK8 Embedded GPS Module 1-3

Starter Kit

The Starter Kit components and the accessory part numbers are listed in Table 1-1 and Table 1-2.

Table 1-1. Lassen-SK8 Starter Kit

Starter Kit Part Reference Part Number

Lassen-SK8 Starter Kit 29467-00 8-channel Lassen-SK8 receiver module (Socketed) 28479-99-D SK8 Interface Unit 28832-10 Magnetic Mount GPS Antenna with Cable 28367-00 AC Power Adapter 29938 Power Cable 20260 Interface Cable DB9M/DB9F 19309-00 GPS Toolkit Disk 30643-01 System Designer Reference Manual 34149-01

Table 1-2. Lassen-SK8 Modules

Starter Kit Part Reference Part Number

Standard Temperature Module 28835-10 Extended Temperature Module 28835-20

Table 1-3. Lassen SK-8 Optional Antennas

Antenna Reference Part Number

Hard Mount GPS Antenna 28367-70 Rooftop Antenna Kit with 75 foot cable 23726-00

Note – Part numbers are subject to change. Confirm part numbers with your Trimble representative when placing your order.

1-4 Lassen-SK8 Embedded GPS Module

1.2 GPS Receiver Module

In the Starter Kit, the Lassen-SK8 is installed on an interface motherboard which is housed in a metal enclosure (see Figure 1-1). This packaging simplifies testing and evaluation of the module by providing an RS-232 serial interface which is compatible with most PC communication ports, and by providing a DC power supply which converts a 9 to 32 volts DC input to the regulated 5 volts required by the module. The DB9 connectors provide an easy connection to the PC's serial port using the interface cable provided in the kit. The metal enclosure protects the module and motherboard for testing outside of the laboratory environment.

Starter Kit

Figure 1-1. The Module Installed Inside the Interface Unit

Lassen-SK8 Embedded GPS Module 1-5

Starter Kit

The receiver module (see Figure 1-2) consists of a single 3.25" x 1.25" x 0.40" module. A standard SMB RF connector (J1) supports the GPS antenna connection. The center conductor supplies +5 VDC for the Low Noise Amplifier of the active antenna. An 8-pin,

0.1 inch header (J4) supports the serial interface (CMOS TTL level), the pulse-per-second (PPS) signal (CMOS TTL level), and the input power (+5 VDC). This module connects to the motherboard via the 8-pin header and is secured by two standoffs. An RF-interface cable connects the antenna port to an SMB connector on the enclosure panel.

Figure 1-2. Receiver Module

Note – The receiver included in the Starter Kit contains a socket for the firmware ROM.

This socketed board may be used to evaluate future releases of firmware. The standard OEM module is not equipped with a socket.

1-6 Lassen-SK8 Embedded GPS Module

Starter Kit

The interface motherboard includes a 9 to 32 VDC switching power supply which provides a regulated +5 VDC to the receiver. It also converts the TTL-level I/O to RS-232 for a direct interface to a computer. The motherboard provides an open-collector interface for the PPS and also includes a 3.6V lithium backup battery enabling lightening-fast hot starts. The Starter Kit includes an AC/DC converter for powering the module from an AC wall socket. The metal enclosure (see Figure 1-3) provides 2 interface port connectors, an antenna connector and a power connector. The mounting plate is secured to the metal enclosure with four screws. The eight pin header plugs into the corresponding 8-pin socket on the motherboard as shown in Figure 1-3.

Figure 1-3. Starter Kit Interface Unit

Note – Due to the open-collector interface, the polarity of the PPS signal is inverted. The

pulse is a 10µs negative-going pulse with the falling edge synchronized to UTC. When removed from the motherboard, the receiver provides a TTL level, positive-going pulse. In order to pull up the 1pps use a 10k pull up resister as shown in the following illustration.

+5Vdc

10K ohm

PORT 1

Pin 9

Figure 1-4. Open Collector PPS

The Starter Kit interface unit provides fifty percent of the duty cycle on the PPS line.

•

PPS

Pin 9

Lassen-SK8 Embedded GPS Module 1-7

Starter Kit

1.3 Antenna

The GPS antenna receives the GPS satellite signals and passes them to the receiver. Because the GPS signals are spread spectrum signals in the 1575 MHz range and do not penetrate conductive or opaque surfaces, the GPS antenna must be located outdoors with a clear view of the sky. The Lassen-SK8 requires an active antenna. The received GPS signals are very low power, approximately -140 dB, at the surface of the earth. Trimble's active antennas include a preamplifier that filters and amplifies the GPS signals before delivery to the receiver.

Trimble offers a variety of antennas for use with the Lassen-SK8. The compact magnetic mount GPS antenna and integral cable supplied with the Starter Kit is ideal for portable and mobile applications. A permanent, bulkhead mount antenna is also available. A compact, pole-mount rooftop antenna is available for fixed-site installations. Refer to Appendix F for mechanical outline drawings of the GPS antennas.

Figure 1-5. Magnetic Mount GPS Antenna

Figure 1-6. Hard Mount GPS Antenna

1-8 Lassen-SK8 Embedded GPS Module

1.4 Power

Starter Kit

Figure 1-7. Bullet II GPS Antenna

The receiver module is designed for embedded applications and requires a regulated +5.0 VDC input (+4.75 to +5.25 VDC). See Power Requirements in Chapter 4 for detailed specifications. In the Starter Kit, the motherboard includes a DC power regulator which converts a 9 to 32 VDC input to the regulated 5 VDC required by the module. Power can be applied to the Starter Kit module using one of two options: the DC power cable (see Figure 1-8) or the AC/DC power converter (see Figure 1-9).

Figure 1-8. DC Power Cable

The DC power cable is ideal for bench-top or automotive testing environments. The power cable is terminated at one end with a 3-pin plastic connector which mates with the power connector on the metal enclosure. The unterminated end of the cable provides easy connection to a DC power supply. Connect the red power lead to a source of DC positive +9 to +32 VDC, and connect the black power lead to ground. This connection supplies power to both the receiver module and the antenna. The combined power consumption of the receiver module and the antenna is 200 milli-amps.

Lassen-SK8 Embedded GPS Module 1-9

Starter Kit

Note – The yellow wire is not used in the Starter Kit. Battery back-up is provided by a factory installed 3.6V lithium battery on the motherboard.

The AC/DC power converter may be used as an alternate power source for the Starter Kit module. The AC/DC power converter converts 110 or 220 VAC to a regulated 12 VDC compatible with the Starter Kit module. The AC/DC power converter output cable is terminated with a 3-pin connector compatible with the power connector on the metal enclosure. The AC power cable is not provided in the kit, since this cable is countryspecific. The input connector is a standard 3-prong connector used on many desktop PCs.

Figure 1-9. AC/DC Power Converter

1.5 Hardware Setup

The Lassen-SK8 supports TSIP, TAIP, and NMEA protocols. Port 1 is used for TSIP or TAIP I/O and port 2 is used to input RTCM corrections and output NMEA messages. Follow the steps below to setup the Starter Kit. Figure 1-10 illustrates the setup.

1. For TSIP or TAIP Protocols, connect one end of the 9-pin serial interface cable to Port 1 (or Port 2 to view NMEA data) of the receiver module. Connect the other end of the cable to COM1 or COM2 on a PC. A 9-pin-to-25-pin adapter may be required for the serial interface connection to a PC, if your PC has a 25-pin communication port.

2. Connect the antenna cable to the interface unit. This connection is made by pushing the antenna cable connector onto the SMB connector on the unit (to remove the antenna cable, simply pull the antenna connector off of the SMB connector). Place the antenna so that it has a clear view of the sky.

3. Using either the DC power cable or AC/DC power converter, connect to the 3-pin power connector on the interface unit.

- DC Power Cable — Connect the terminated end of the power cable to the

power connector on the interface unit. Connect the red lead to DC positive voltage (+9 to +32 VDC) and black power lead to DC ground. The yellow wire is not used. Switch on the DC power source.

1-10 Lassen-SK8 Embedded GPS Module

Starter Kit

Power Converter

Electrical

- AC/DC Power Converter — Connect the output cable of the converter to the

3-pin power connector on the interface unit. Using the appropriate 3-prong AC power cable (not provided), connect the converter to an AC wall socket (110 VAC or 220 VAC). The AC power cable is not provided in the Starter Kit.

Antenna

Figure 1-10. Interconnect Diagram

1.6 Running the TSIP Interface Program

The Starter Kit includes a disk containing TSIP interface programs which run on a PCDOS platform. These programs aid system integrators in monitoring the receiver module's performance and in developing the software interface for the GPS module. The TSIP programs are described in detail in Appendix B, TSIP User's Guide.

1. Connect one end of the serial interface cable to Port 1 of the Starter Kit interface unit. Connect the other end of the cable to COM1 or COM 2 of your PC.

2. Turn on the DC power source or plug in the AC/DC converter.

3. Turn on the PC.

4. Insert the GPS Tool Kit disk in the disk drive.

5. Go to the directory where you wish to establish the GPS tool kit sub directory. In most cases, this will be the root directory on the C: drive.

Note – For detailed installation guidelines, read the install text file A:\README.TXT. The toolkit disk contains a self-extracting zip file that installs the program onto your DOS computer.

Lassen-SK8 Embedded GPS Module 1-11

Starter Kit

6. At the DOS prompt, type A:\INSTALL. The executable program creates a sub directory called TOOLKIT and installs the tool kit files.

7. Type the appropriate path name to execute the TSIPCHAT program (e.g.

C:\TOOLKIT\TSIPCHAT). TSIPCHAT provides full access to the TSIP protocol. It

converts binary TSIP packets into printable ASCII characters and vice versa. When TSIPCHAT is initiated, it configures the PC serial port to the default TSIP settings (9600 baud, 8-Odd-1).

8. After the TSIPCHAT title screen appears, press [?], and the primary TSIPCHAT screen shown in Figure 1-11 is displayed.

9. To test the connection, press [V]. This message requests the firmware version numbers from the GPS module. If connected and operating properly, the module should respond with a software version report within one second. This report will be displayed in the command window.

When a GPS antenna is connected to a receiver and has achieved a position fix, the transmitted position reports scroll through the report window (see Figure 1-11). These reports include position, velocity and other GPS information. A receiver health report is sent every few seconds, even when no satellites are being tracked.

Figure 1-11. TSIPCHAT Command Window and Report Window

The upper (shaded) portion of the screen is the command/response window and the lower portion of the screen is the automatic report window (auto window). The auto window displays a running account of the messages which are automatically output by the GPS module in the lower half of the screen. The most common reports are the position and velocity reports. Other automatic reports include receiver status and health information.

1-12 Lassen-SK8 Embedded GPS Module

Starter Kit

When the GPS module has completed a position fix and starts transmitting position reports, the position reports will begin scrolling in the auto window. An automatic receiver health report is sent every few seconds, even when no satellites are being tracked.

If the auto window is not displaying messages, then the GPS module may not be connected properly to the computer. To test the connection, press [V].

If the message, WAITING FOR REPLY appears continuously in the command window, then the GPS module is not communicating with the computer. If this occurs, re-check the interface cable connections and verify the serial port selection. If the communication failure still occurs after checking all connections and settings, please call the Trimble Technical Assistance Center (TAC) for assistance.

Lassen-SK8 Embedded GPS Module 1-13

Starter Kit

1-14 Lassen-SK8 Embedded GPS Module

2 Hardware Integration

The integration of the Lassen-SK8 receiver module is discussed in two sections: Hardware Integration and Software Interface. This chapter, Hardware Integration, includes instructions for mounting the GPS module and physically connecting the module to the antenna, the host processor, and the power source. Chapter 3, Software Interface, provides guidelines for configuring the Lassen-SK8 receiver module to communicate with the host processor.

2.1 The Lassen-SK8 Receiver Module

In the Starter Kit, the Lassen-SK8 receiver module is installed on the interface motherboard to facilitate testing and evaluation. The receiver module can be detached from the motherboard for installation into a specific device.

The receiver module is connected to the motherboard at four points: the antenna connector, the interface connector, and two standoffs (see Figure 2-1). Follow the steps below to remove the receiver module from the motherboard.

Figure 2-1. Motherboard Connection Points

Lassen-SK8 Embedded GPS Module 2-1

Hardware Integration

Caution – Before disassembling the interface unit, disconnect the unit from any external power source and confirm that both you and your work surface are properly grounded for ESD protection. The interface unit motherboard contains a 3.6V lithium battery. Exercise caution when removing it from the Lassen-SK8 unit.

1. Remove the four screws which secure the bottom plate to the base of the metal enclosure. Set the bottom plate aside.

2. Remove the two screws securing the Lassen-SK8 module to the standoffs on the motherboard. These screws are located at opposite ends of the receiver module (see Figure 2-2)

Figure 2-2. Removing the Receiver Module

3. Carefully pull the module straight off the motherboard to disengage the 8-pin header from the 10-pin socket on the motherboard (see Figure 2-2). Do not rotate or flex the module while disengaging the header, since this could damage the connector or the board components. Pull straight up, keeping the Lassen-SK8 parallel to the motherboard.

4. Disconnect the RF cable connecting the Lassen-SK8 module to the SMB connector on the enclosure. This connection was made by pushing the antenna cable connector onto the SMB connector on the receiver. To remove the antenna cable, grasp the cable connector and pull it straight off of the antenna connector. Do not twist the cable or attempt to pull it off at an angle, as this may damage the connector.

5. To reinstall the Lassen-SK8 board in the motherboard, follow steps 1 - 4 in reverse order.

Note – The Lassen-SK8 is designed for embedded applications. The digital I/O lines and power lines are not designed with additional ESD protection as a stand-alone module would be. Use standard CMOS ESD handling precautions when removing and installing the receiver module.

2-2 Lassen-SK8 Embedded GPS Module

2.2 Interface Connector

The Lassen-SK8 power and data I/O functions are integrated into a single 8-pin header connector, J4. The J4 connector uses 0.025 inch pins on 0.10 inch spacing (refer to the mechanical outline drawing in Appendix F).

Table 2-1. I/O Connector Signals

Pin # Function Description

1 TXD 2 Port 2 transmit, CMOS/TTL 2 Prime Power 5VDC ±5%, 150 mA typical 3 TXD 1 Port 1 transmit, CMOS/TTL 4 Backup Power +3.2VDC to +5.25VDC, 2uA typical 5 RXD 1 Port 1 receive, CMOS/TTL 6 1 PPS Pulse-Per-Second, CMOS/TTL 7 RXD 2 Port 2 receive, CMOS/TTL 8 GND Ground, Power and Signal

Pins 3 and 5 on J4 are also referred to as the primary serial port. Pins 1 and 7 are also referred to as the secondary serial port.

Hardware Integration

Figure 2-3. Interface Connector Pin Identification

2.3 Power Requirement

The Lassen-SK8 receiver module requires +5 volts DC ±5% at 150 mA, typically excluding the antenna. For power-on surge design considerations, the prime power should be able to source up to a maximum load of 200 mA. The on-board capacitance on prime power is 10 µF. An important design consideration for power is the receiver module's internal clock frequency at 12.504 MHz ± 3 KHz. Interference spurs on prime power in this narrow frequency band should be kept to less than 1mV.

Lassen-SK8 Embedded GPS Module 2-3

Hardware Integration

The receiver does not require any special power up or down sequencing. The receiver power is supplied through pin 2 of the I/O connector. Refer to Table 2-2 for the +5 VDC power specifications.

The Lassen-SK8 module provides an input for battery back-up (BBU) power to keep the module's RAM memory alive and to power the real-time clock when the receiver's prime power is turned off. RAM memory is used to store the GPS almanac, ephemeris, and last position. User configuration data, including port parameters and receiver processing options, are stored in non-volatile EEROM which does not require back-up power. By using battery back-up, time to first fix is reduced to 20 seconds (typical). Though not required, providing BBU power can reduce power-on time. A 3.6 volt lithium battery used for back-up power can last up to five years.

Note – 3.2V is the minimum allowable voltage. When the power output drops below 3.2V, the real-time clock may not operate over the specified full temperature range.

Table 2-2. Power Requirements

Signal Voltage Current J4 Pin

VCC +4.75 to +5.25 200 mA 2 Battery Backup +3.2 to +5.25 0uA with prime power; 2uA

@ 3.5V, 25°C without prime power

Ground 0 - 8

The Lassen-SK8 receiver module will maintain full performance specification when the prime power line is coupled with less than 100 mV of ripple noise, peak to peak from 1Hz to 1MHz.

Note – The Lassen-SK8 Starter Kit motherboard contains a 3.6V lithium battery.

2.4 Serial Interface

As an embedded design, the Lassen-SK8 receiver module provides direct CMOS compatible TTL level serial I/O. The RX and TX signals on the J4 I/O connector are driven directly by the DUART on the Lassen-SK8. Interfacing these signals directly to a DUART in your application circuitry provides direct serial communication without the complication of RS-232 or RS-422 line drivers.

2-4 Lassen-SK8 Embedded GPS Module

Note – The serial I/O signals on J4 are TTL level. They are not inverted or driven to RS232 levels.

2.5 Pulse Per Second

A ten microsecond wide, CMOS compatible TTL level pulse is available on pin 6 of the J4 I/O connector. This pulse is issued once per second with the rising edge of the pulse synchronized with UTC. The pulse will be shaped by the distributed impedance of the attached signal line and input circuit. The rising edge is typically less than 20 nSec. The falling edge should not be used.

The timing accuracy is ± 100 nanosecond (1Σ) and is available only when valid position fixes are being reported. Repeatability checks of 10 sets of 100 one second samples taken over a period of 20 minutes showed an average variation of approximately 100 nanoseconds (not allowing for SA).

2.6 Mounting

The Lassen-SK8 provides four 0.125 inch mounting holes that will accept 3/16 inch round or hex standoffs with 3/8 inch height, and #4 or M3 mounting screws. Space constrained environments may require a different stand-off. Refer to the mechanical outline drawing in Appendix F for dimensions and clearances.

Hardware Integration

2.7 RF Shield

An optional RF shield is available for production versions of the standard temperature Lassen-SK8 module. The production versions of the Lassen-SK8 do not have a socketed EPROM. This RF shield protects the GPS module from interference with other electronics and also makes the module compliant with the CE emission specification. The RF shield is not compatible with the socketed board provided in the Starter Kit nor with the extended temperature board that has a TCXO oscillator.

Note – Many installations do not require the optional shield. The Lassen-SK8 is designed to be immune to most interference.

Lassen-SK8 Embedded GPS Module 2-5

Hardware Integration

2-6 Lassen-SK8 Embedded GPS Module

3 Software Interface

This chapter describes the Lassen-SK8 software interface, the start-up characteristics for the interface protocols, a description of the receiver operating modes, and a brief discussion of the interface protocols.

3.1 Start-up

ACE GPS is a complete 8-channel parallel tracking GPS receiver designed to operate with the L1 frequency, standard position service, Coarse Acquisition code. Using two highly integrated Trimble custom integrated circuits, the receiver is designed in a modular format especially suited for embedded applications.

When connected to an external GPS antenna, the receiver contains all the circuitry necessary to automatically acquire GPS satellite signals, track up to 8 GPS satellites, and compute location, speed, heading, and time. The receiver will automatically begin to search for and track GPS satellite signals at power-up.

The performance of a GPS receiver at power-on is determined largely by the availability and accuracy of the satellite ephemeris data and the availability of a GPS system almanac. Refer to Chapter 4 for additional information. The first time the receiver is powered-up, it is searching for satellites from a cold start (no almanac). While the receiver will begin to compute position solutions within the first two minutes, it actually takes the receiver about 15 minutes to download a complete almanac. This initialization process should not be interrupted. With a complete almanac and back-up power, the time to first fix can typically be shortened to less than 20 seconds. The receiver will respond to commands almost immediately after power-up.

3.2 Software Tool Kits

Trimble provides a Software Developers Tool Kit to support the TSIP and TAIP protocols. The Kit contains a user-friendly program to communicate with the receiver and includes sample C source code and reusable routines to aid in developing applications. The following Appendices provide additional information:

• TSIP

- Appendix A, Trimble Standard Interface Protocol

- Appendix B, TSIP User's Guide

• TAIP

- Appendix D, GPSSK User's Guide (TAIP)

- Appendix E, NMEA 0183.

Lassen-SK8 Embedded GPS Module 3-1

Software Interface

3.3 Communicating with the Lassen-SK8 Module

The Lassen-SK8 supports three I/O message protocols: TSIP, TAIP, and NMEA. The protocols are discussed at the end of this chapter, and are explained in detail in Appendices A through E.

Communication with the Lassen-SK8 module is through two CMOS compatible, TTL level serial ports. The port characteristics can be changed to accommodate your application requirements. Port parameters are stored in a non-volatile electrically erasable ROM (EEROM) that does not require backup power. Table 3-1 lists the default characteristics for each port.

Table 3-1. Default Serial Port Characteristics

Input

Port

1 TAIP Baud Rate: 4800

1 TSIP Baud Rate: 9600

2 RTCM Baud Rate: 4800

Protocol Default Setup

Data Bits: 8 Parity: Odd Stop Bits: 1 No Flow Control

Data Bits: 8 Parity: None Stop Bits: 1 No Flow Control

Output Language Default Setup

TAIP Baud Rate: 4800

Data Bits: 8 Parity: Odd Stop Bits: 1 No Flow Control

TSIP Baud Rate: 9600

Data Bits: 8 Parity: Odd Stop Bits: 1 No Flow Control

NMEA Baud Rate: 4800

Data Bits: 8 Parity: None Stop Bits: 1 No Flow Control

Any standard serial communications program, such as Windows Terminal or PROCOMM, can be used with the TAIP or NMEA interface protocol. TSIP is a binary protocol and outputs raw serial data onto the screen which cannot be read. Trimble encourages the use of the DOS compatible software tool kit provided for TSIP. The serial port drivers in the Trimble tool kit, TSIPCHAT, match the Lassen-SK8 serial port characteristics. The TSIPPRNT program converts binary data logged with the TSIPCHAT program into ASCII characters that may be printed and displayed.

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Warning – When using the TSIP protocol to change port assignments or characteristics, confirm that your changes do not affect the ability to communicate with the receiver module.

3.4 Protocol Summary

The Lassen-SK8 receiver is shipped from the factory with the following configuration:

• TSIP

- 9600 baud 8-odd-1 on Port 1

• NMEA out/RTCM in

- 4800 baud 8-none-1 on Port 2

The receiver can easily be reconfigured for other combinations of language and port baud rate and parity. These settings are kept in BBRAM (Battery Backed Random Access Memory) and can be saved into non-volatile memory if desired. The commands include:

• TSIP command: 0xBC

• TAIP command: PT

Refer to Appendix A.3, Customizing Receiver Operations, for additional information on protocols.

If the receiver is not talking to application programs, the ports may be configured to an unknown setting. Use the following Toolkit program commands to return the receiver to the factory default setting:

Software Interface

• TSIP: SK8BREAK

• TAIP: SK8TAIP

3.4.1 TSIP Data Output

The Trimble Standard Interface Protocol (TSIP) is the native language for the LassenSK8. TSIP is a binary language, with a wide variety of commands and reports. TSIP reports can be output automatically, or they can be output as responses to queries. The format of the automatic reports can be easily configured. Refer to Appendix A.3, Customizing Receiver Operations and Appendix A.4, Automatic Position and Velocity Reports for further information. The receiver is shipped from the factory configured for single precision Latitude-Longitude-Altitude. Customized position and velocity formats can be created by using the information in Appendix A.3, Customizing Receiver Operations.

The TSIPCHAT program in the Lassen-SK8 Starter Kit permits using a computer keyboard to send the Request Packets to the GPS receiver. The responses to these requests are then displayed on a DOS computer screen in ASCII format. C source code routines for the

TSIPCHAT program are also provided in the Starter Kit. C source can be used as a

software design guide by programmers who need to communicate system integration information with the Lassen-SK8.

Lassen-SK8 Embedded GPS Module 3-3

Software Interface

Configuring the ACE GPS receiver output protocol from TSIP to TAIP protocol.

TSIP command packet 0xBC can be configured in accordance with the following procedure:

1. Run TSIPCHAT -Cx (Where x = Host Computer COM Port).

2. Once TSIPCHAT is running: a. Press [?]. The following will be displayed:

Keystroke Command List

3. Initiate the 0xBC Command Packet. Refer to Packet BC in the Appendix A, Trimble Standard Interface Protocol for further information.

a. Press [U] b. Press the [SPACE{BAR] to cycle through the options. Enter the following: c. Set (1) d. Press [Enter]

4. Select the Port to be configured: Do the following: a. Press the [SPACE{BAR] to cycle through the options

b. Select Port 1 (0) c. Press [Enter]

5. Set the Receiver Port configuration Input Baud rate: a. Press the [SPACE{BAR] to cycle through the options

b. Make a selection c. Press [Enter]

6. Set the Receiver Port configuration Output Baud Rate: a. Cycle through the options by pressing the [SPACE{BAR]

b. Select the Output Baud Rate c. Press [Enter]

7. Set the Data Bits. a. Select the appropriate Data Bits. TAIP is the default: TAIP =8.

b. Press [Enter]

8. Set Parity. a. Select the appropriate Parity. TAIP is the default: TAIP =Odd.

b. Press[Enter]

9. Set Stop Bits.X a. Select the appropriate Stop Bits. TAIP is the default: TAIP =8:

b. Press [Enter]

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Software Interface

10. Set the Flow Control a. Press the [SPACE{BAR] to cycle through the options

b. Select the appropriate Flow Control. TAIP is the default: TAIP =Off c. Press[Enter]

11. Set Protocol In: a. Press the [SPACE{BAR] to cycle through the options

b. Select TAIP (0) c. Press [Enter]

12. Set Protocol Out: a. Press the [SPACE{BAR] to cycle through the options

b. Select TAIP (0) c. Press [Enter]

13. If satisfied with these selections: a. Press [Y] — Saves the configuration

b. Press [N] — Aborts the configuration and displays the message: ABORTED

3.4.2 TAIP Data Output

The Trimble ASCII Interface Protocol (TAIP) is a Trimble-specified digital communication interface based on printable ASCII characters over a serial data link. TAIP interface provides the means to configure the Lassen-SK8 receiver to output various sentences in response to query or on a scheduled basis. TAIP messages may be scheduled for output at a user specified rate starting on a given epoch from top of the hour. For communication robustness, the protocol optionally supports checksums on all messages. It also provides the user with the option of tagging all messages with the unit's user specified identification number (ID). This greatly enhances the functional capability of the unit in a network environment. This protocol is described in Appendix C, Trimble ASCII Interface Protocol (TAIP).

The receiver can easily be configured to TAIP with the program SK8TAIP contained in the Toolkit. This program re-configures the Lassen-SK8 to Default TAIP settings: TAIP at 4800 8-none-1 on Port 1, RTCM in / silent out at 4800 8-none-1 on Port 2. The program stores these settings, along with all the other defaults, to non-volatile memory. The GPSSK program can now be used to control and re-configure the receiver.

Receiver configurations created in GPSSK can be stored in non-volatile memory using the RT command. As mentioned above, the receiver ports can also be set to TAIP through a TSIP port using TSIPCHAT and the TSIP command 0xBC.

Lassen-SK8 Embedded GPS Module 3-5

Software Interface

Configuring the ACE GPS receiver output protocol from TAIP to TSIP protocol TAIP message PR

Configuring the receiver output from TAIP to TSIP will display binary data in now displayed on the screen.

Where:

Table 3-2. TSIP Message Description

1. Run GPSSK /x. Press [x] to select the Host Computer COM Port

2. When the GPS Main screen appears, press [ENTER]

3. Type the following message to set the receiver to TSIP.

>SPR;TAIP=FF;TSIP=TF;<

ELEMENT DESCRIPTION

> Beginning of command sentence S The Set Command PR The TAIP protocol message TSIP The desired protocol FF Port 1 off

Port 2 off

TF Port 1 in /out

Port 2 off

I/O Port 1 in

Port 2 output

< End of command sentence

4. Press [ENTER] to complete the change

Use TSIPCHAT to make additional changes.

3.4.3 NMEA 0183 Data Output

The National Marine Electronics Association (NMEA) protocol is an industry standard data protocol which was developed for the marine industry. Trimble has chosen to adhere stringently to the NMEA 0183 data specification as published by the NMEA. Although the Trimble Lassen-SK8 supports seven NMEA sentences that contain GPS information, the standard Lassen-SK8 only outputs the GGA and VTG data strings.

3-6 Lassen-SK8 Embedded GPS Module

Note – Contact your Trimble sales representative if you need access to all or a subset of the other five NMEA sentences.

NMEA data is output in standard ASCII sentence formats. Message identifiers are used to signify what data is contained in each sentence. Data fields are separated by commas within the NMEA sentence. In the Lassen-SK8, NMEA is an output only protocol. The NMEA protocol is described in detail in Appendix E, NMEA 0183.

The receiver is shipped from the factory with NMEA output on Port 2. Port 2 settings can be changed using TSIPCHAT and command 0xBC. TSIP command 0x7A changes the NMEA output sentences and output rates. The new settings are saved to BBRAM or they can be saved to non-volatile memory using TSIP command 0x8E-26.

3.5 Timing Applications

The Lassen-SK8 is an excellent source for accurate system timing. Examples of applications requiring accurate time are environmental data acquisition or synchronization of communications networks. The timing functions of the receiver are supported by the TSIP protocol. See Report Packet 41 in Appendix A for a description of the time function reports for TSIP.

Software Interface

Note – Note that GPS time differs from UTC (Universal Coordinated Time) by a variable integer number of seconds: UTC = (GPS time) - (GPS UTC Offset)

As of July 1997, the GPS UTC offset was 12 seconds. The offset increases by 1 second approximately every 18 months. System designers should plan to read the offset value as a part of the timing interface to obtain UTC. The GPS week number is in reference to a base week (Week #0), starting January 6, 1980.

The current GPUSTC offset is contained within the almanac transmitted by the GPS system. The Lassen-SK8 must have a complete almanac before the offset data is valid.

3.5.1 Effect of GPS Week Number Roll-over (WNRO)

At 0000 hours Greenwich Mean Time (GMT) on 21/22 August 1999, the GPS Week Number will roll-over from 1023 to zero. Trimble receivers have numerous built-in protections to prevent this from being a catastrophic event. Systems may benefit however, from extra care with the first power-up after WNRO.

Note – GPS Week Numbers occupy a range from zero to 1023 such that the Week Number Roll Over (WNRO) occurs every 1024 weeks, or approximately every 19 years 8 months. August 1999 is the first roll-over for the GPS system since the beginning of GPS time on 06 January 1980.

Lassen-SK8 Embedded GPS Module 3-7

Software Interface

The following two known issues for previous versions of receivers exist as a result of testing a representative sample of Trimble OEM receivers.

There is no impact for TSIP users on position or time information. The reported GPS week number will reset to zero however, and users that require this information may need to make a software modification to accommodate this change.

ACE GPS/Palisade Family Firmware Version 7.xx Software Modifications

The Lassen-SK8 receiver has been designed to handle WNRO and there are no problems with either dates or the first fix after WNRO through the year 2015.

• An almanac recorded prior to WNRO is not correct after WNRO. This problem only exists when the receiver main power is OFF and battery back-up power is ON at the moment of WNRO. Once the receiver is cold started, a post-WNRO almanac is collected and the receivers behavior returns to normal.

• Day-month-year representations will be incorrect after WNRO when using specific TAIP and NMEA messages. Time and day information will not be effected however.

Caution – Trimble OEM GPS receivers have reported the true GPS Week Number in TSIP messages 0x41 and 0x8F-20 as a number between 0 and 1023. The Lassen-SK8 however, outputs the Extended GPS Week Number as the absolute number of weeks since the beginning of GPS time or 06 January 1980. If the true GPS Week Number is desired, the system developer should ignore the extra MSBs of the Extended GPS Week Number and use only the 10 LSBs.

3.6 Differential GPS

The Lassen-SK8 module can use differential corrections to compute a Differential GPS position (DGPS). DGPS can provide position accuracy of 2 meters (1 sigma).

RTCM SC-104, the industry standard format for differential corrections, is available from most DGPS reference stations, Coast Guard beacon transmissions, and commercial DGPS subscription services. The Lassen-SK8 is fully compatible with RTCM SC-104 Version

2.1. The Lassen-SK8 is configured to accept RTCM SC-104 correction data over port 2 (J4, pin 7) at 4800 baud, 8 data bits, 1 stop bit and no parity. The DGPS operating mode is set to Automatic which means that the receiver will provide differential GPS solutions when valid correction data is available and will output standard GPS solutions when no valid correction data is available.

No setup is required to use RTCM SC-104 differential corrections, however, you may need to reconfigure the serial port characteristics (baud rate, data bits, stop bits and parity) to match the characteristics of your RTCM SC-104 data source using the TSIP packet BCh. See Appendix A for more information on this message. Table 3-1 summarizes the default characteristics for the Lassen-SK8 serial ports.

3-8 Lassen-SK8 Embedded GPS Module

Software Interface

Alternatively, you may use Trimble's TSIP packets 60h and 61h to apply differential corrections through the Lassen-SK8 port 1 (J4, pin 5). These packets can be interleaved with the TSIP command stream. Packets 60h and 61h are useful in applications which require the use of a single communications channel between the Lassen-SK8 and the system. Note that using these messages requires you to reformat the RTCM SC-104 differential correction data into the 60h/61h message format. See Appendix A for more information on these messages.

Lassen-SK8 Embedded GPS Module 3-9

Software Interface

3-10 Lassen-SK8 Embedded GPS Module

4 Operation and Performance

This chapter describes the Lassen-SK8 satellite acquisition and tracking processes, performance characteristics and system architecture. This discussion assumes that you are familiar with the basic theory of the Global Positioning System. Before proceeding to the detailed discussion of the satellite acquisition and tracking process, please review the GPS satellite message description on the next page.

The Lassen-SK8 satellite acquisition and tracking algorithms can achieve a position solution without any initialization. The receiver automatically selects and tracks the best combination of satellites to compute position and velocity. As satellites move out of view, the Lassen-SK8 automatically acquires new satellites and includes them in the solution set as required.

4.1 GPS Satellite Message

Every GPS satellite transmits the Coarse/Acquisition (C/A) code and satellite data modulated onto the L1 carrier frequency (1575.42 MHz). The satellite data transmitted by each satellite includes a satellite almanac for the entire GPS system, its own satellite ephemeris and its own clock correction.

The satellite data is transmitted in 30-second frames. Each frame contains the clock correction and ephemeris for that specific satellite, and two pages of the 50-page GPS system almanac. The almanac is repeated every 12.5 minutes. The ephemeris is repeated every 30 seconds.

The system almanac contains information about each of the satellites in the constellation, ionospheric data, and special system messages. The GPS system almanac is updated weekly and is typically valid for months. The ephemeris contains detailed orbital information for a specific satellite. Ephemeris data changes hourly, but is valid for up to four hours. The GPS control segment updates the system almanac weekly and the ephemeris hourly through three ground-based control stations. During normal operation, the Lassen-SK8 module updates its ephemeris and almanac as needed.

The performance of a GPS receiver at power-on is determined largely by the availability and accuracy of the satellite ephemeris data and the availability of a GPS system almanac.

Lassen-SK8 Embedded GPS Module 4-1

Operation and Performance

4.2 Satellite Acquisition and Time to First Fix

4.2.1 Cold-Start

The term “cold-start” describes the performance of a GPS receiver at power-on when no navigation data is available. “Cold” signifies that the receiver does not have a current almanac, satellite ephemeris, initial position, or time. The cold-start search algorithm applies to a Lassen-SK8 which has no memory of its previous session (i.e., is powered on without the memory backup circuit connected to a source of DC power). This is the “out of the box” condition of the GPS module as received from the factory.

In a cold-start condition the receiver automatically selects a set of eight satellites and dedicates an individual tracking channel to each satellite, to search the Doppler range frequency for each satellite in the set. If none of the eight selected satellites is acquired after a pre-determined period of time (time-out), the receiver will select a new search set of eight satellites and will repeat the process, until the first satellite is acquired. As satellites are acquired, the receiver automatically collects ephemeris and almanac data. The Lassen-SK8 uses the knowledge gained from acquiring a specific satellite to eliminate other satellites, those below the horizon, from the search set. This strategy speeds the acquisition of additional satellites required to achieve the first position fix.

The cold-start search sets are established to ensure that at least three satellites are acquired within the first two time-out periods. As soon as three satellites are found, the receiver will compute an initial position fix. The typical time to first fix is less than 2 minutes.

A complete system almanac is not required to achieve a first position fix. However, the availability and accuracy of the satellite ephemeris data and the availability of a GPS almanac can substantially shorten the time to first fix.

Note – When installed in the interface unit, the Lassen-SK8 receives back-up power from a lithium battery. This battery enables the Lassen-SK8 to always start from either a warm or hot start. To force a cold start, issue the 1E TSIP command ([Control] + [K] in the TSIP chat program on the GPS toolkit diskette in the Starter Kit).

4.2.2 Warm Start

In a warm start condition, the receiver has been powered down for a period of 1-6 hours but has a current almanac and an initial position and time stored in memory.

When connected to an external backup battery and power is applied, the Lassen-SK8 retains the almanac, approximate position, and time to aid in satellite acquisition and reduce the time to first fix. When an external back-up battery is not used, the TSIP protocol allows the almanac, an initial position, and time to be uploaded to the receiver via the serial port, to initiate a warm start.

During a warm start, the Lassen-SK8 identifies the satellites which are expected to be in view, given the system almanac, the initial position and the approximate time. The receiver calculates the elevation and expected Doppler shift for each satellite in this expected set and directs the eight tracking channels in a parallel search for these satellites.

4-2 Lassen-SK8 Embedded GPS Module

The warm start time to first fix, when the receiver has been powered down for more than 60 minutes (i.e. the ephemeris data is old) is usually less than 45 seconds.

4.2.3 Garage Search Strategy

During a warm start search, the Lassen-SK8 knows which satellites to search for, based on the system almanac, the initial position (last known position) and the current time. In some cases, the receiver may not be able to acquire the expected satellite signals (e.g. a vehicle parked in a garage or a vessel in a covered berth). Trimble's patented “garage search” strategy, also known as a split search, is designed for such situations.

If the receiver does not acquire the expected set of satellites within 5 minutes of power-on, some of the eight tracking channels will continue to search for the expected satellites (warm search) while the remaining channels are directed in a cold start search. This strategy minimizes the time to first fix in cases where the stored almanac, position and time are invalid. The stored information is flushed from memory, if the cold start search proves effective and the warm search fails.

4.2.4 Hot Start

Operation and Performance

A hot start strategy applies when the Lassen-SK8 has been powered down for less than 60 minutes, and the almanac, position, ephemeris, and time are valid. The hot start search strategy is similar to a warm start, but since the ephemeris data in memory is considered current and valid, the acquisition time is typically less than 20 seconds.

4.3 Satellite Mask Settings

Once the Lassen-SK8 has acquired and locked onto a set of satellites, which pass the mask criteria listed in this section, and has obtained a valid ephemeris for each satellite, it will output regular position, velocity and time reports according to the protocol selected.

The default satellite masks observed by the Lassen-SK8 are listed in Table 4-1. These masks serve as the screening criteria for satellites used in fix computations and ensure that position solutions meet a minimum level of accuracy. The Lassen-SK8 will only output position, course, speed and time when a satellite set can be acquired which meets all of the mask criteria. The satellite masks can be adjusted in GPS receivers accepting the TSIP protocol. (See the section titled Key Setup Parameters, located in Appendix A.)

Table 4-1. Default Satellite Mask Settings

Mask Setting

Elevation 5° SNR 2 PDOP 10 PDOP Switch 5

Lassen-SK8 Embedded GPS Module 4-3

Operation and Performance

4.3.1 Elevation Mask

Satellites below a 5° elevation are not used in the position solution. Although low elevation satellites can contribute to a lower/better PDOP, the signals from low elevation satellites are poorer quality, since they suffer greater tropospheric and ionospheric distortion than the signals from higher elevation satellites. These signals travel further through the ionospheric and tropospheric layers.

In addition, low elevation satellites can contribute to frequent constellation switches, since the signals from these satellites are more easily obscured by buildings and terrain. Constellation switches can cause noticeable jumps in the position output. Since worldwide GPS satellite coverage is generally excellent, it is not usually necessary to use satellites below a 5° elevation to improve GPS coverage time. In some applications, like urban environments, a higher mask may be warranted to minimize the frequency of constellation switches and the impact of reflected signals.

4.3.2 SNR Mask

Although the Lassen-SK8 is capable of tracking signals with SNRs as low as 0, the default SNR mask is set to 3 to eliminate poor quality signals from the fix computation and minimize constellation switching. Low SNR values may result from:

• Low Elevation Satellites

• Partially Obscured Signals (e.g. Dense Foliage)

• Multi-Reflected Signals (Multi-Path)

The distortion of signals and the frequent constellation switches associated with lowelevation satellites were discussed above. In mobile applications, the attenuation of signals by foliage is typically a temporary condition. Since the Lassen-SK8 can maintain lock on signals with SNRs as low as 0, it offers excellent performance when traveling through heavy foliage.

Multi-reflected signals, also known as Multi-path, can degrade the position solution. Multi-path is most commonly found in urban environments with many tall buildings and a preponderance of mirrored glass, which is popular in modern architecture. Multi-reflected signals tend to be weak (low SNR value), since each reflection attenuates the signal. By setting the SNR mask to 2 or higher, the impact of multi-reflected signals is minimized.

4.3.3 PDOP Mask

Position Dilution of Precision (PDOP) is a measure of the error caused by the geometric relationship of the satellites used in the position solution. Satellite sets which are tightly clustered or aligned in the sky will have a high PDOP and will contribute to a lower position accuracy. For most applications, a PDOP mask of 10 offers a satisfactory tradeoff between accuracy and GPS coverage time. With world-wide GPS coverage now available, the PDOP mask can be lowered even further for many applications without sacrificing coverage. For differential GPS applications, PDOP related error can be the major contributor to position error. For differential GPS applications requiring the highest level of accuracy, the PDOP mask should be set to 7 or below.

4-4 Lassen-SK8 Embedded GPS Module

4.3.4 PDOP Switch

The default positioning mode for the Lassen-SK8 is Automatic. In this mode, the receiver attempts to generate a 3-dimensional (3D) position solution, when four or more satellites meeting the mask criteria are visible. If such a satellite set cannot be found, the receiver will automatically switch to 2-dimensional (2D) mode. The PDOP switch establishes the trade-off between 3D positioning and PDOP. With the PDOP Switch set to 6, the receiver will compute a 2D position with a HDOP below 6 rather than a 3D position with a PDOP greater than 6, even when four or more satellites are visible.

Operation and Performance

Note – PDOP Switch is only used in Auto mode. If the PDOP Switch is greater than the PDOP Mask, it will stay in 3D mode.

4.4 Standard Operating Modes

The tracking mode controls the allocation of the receiver's tracking channels and the method used for computing position fixes. The output of GPS data is controlled by two operating modes:

• Fix Modes (2D, 3D, or Automatic)

• Differential GPS Mode (On, Off, or Auto)

Each of these operating modes is described below.

4.4.1 Fix Modes

The Lassen-SK8 offers three positioning modes: 2D Manual, 3D Manual, and Automatic 2D/3D. Automatic 2D/3D is the default mode for the Lassen-SK8. The positioning mode can be modified in receivers accepting TSIP commands. See Appendix A for more information on the TSIP protocol.

2D Manual

In 2D Manual mode, the Lassen-SK8 will only generate 2-dimensional (2D) position solutions (latitude and longitude only), regardless of the number of visible satellites. If the altitude is not entered, the receiver uses mean sea level as the default altitude. The greater the deviation between the actual and default altitudes, the greater the error in the 2D position. For TSIP applications, enter local altitude in MSL/HAE via TSIP packet 2AH (see Appendix A).

Lassen-SK8 Embedded GPS Module 4-5

Note – 2D Manual mode is not recommended for differential GPS applications since any deviation in altitude will cause a significant error in the latitude and longitude. Only use the 2D Manual mode for flat land or marine applications where the elevation is known or constant. For DGPS applications, the 3D Manual mode is the recommended positioning mode for the highest level of accuracy.

Operation and Performance

3D Manual

In 3D Manual mode, the Lassen-SK8 will only generate 3-dimensional (3D) position solutions (latitude, longitude, and altitude). A 3D solution requires at least four visible satellites which pass the mask criteria. If less than four conforming satellites are visible, the Lassen-SK8 will suspend position data outputs. 3D Manual mode is recommended for differential GPS applications requiring the highest level of accuracy.

2D/3D Automatic

The default operating mode for the Lassen-SK8 is 2D/3D Automatic. In this mode, the Lassen-SK8 attempts to generate a 3-dimensional (3D) position solution, if four or more satellites meeting the mask criteria are visible. If only three satellites are visible which meet the mask criteria, the Lassen-SK8 will automatically switch to 2-dimensional (2D) mode and will use the last calculated altitude, if available, or the default altitude in the position solution. In 2D/3D Automatic mode, the PDOP switch is active.

4.5 Differential GPS Operating Modes

The default mode for the Lassen-SK8 is DGPS Automatic. The Lassen-SK8 supports three DGPS Modes: On, Off, and Automatic, and the mode may be changed by issuing the appropriate TSIP command. See Appendix A for information on TSIP commands. The three DGPS operating modes are described below.

4.5.1 DGPS On

When DGPS On is selected, the Lassen-SK8 will only provide differential GPS solutions. If the source of correction data is interrupted or becomes invalid, the Lassen-SK8 will suspend all output of position, course and speed data. When a valid source of correction data is restored, the Lassen-SK8 will resume outputting corrected data.

4.5.2 DGPS Off

When DGPS Off is selected, the Lassen-SK8 will not provide differential GPS solutions, even if a valid source of correction data is supplied. In this mode, the receiver will only supply standard GPS data.

4.5.3 DGPS Automatic

DGPS Automatic is the default operating mode for the Lassen-SK8. In this mode, the Lassen-SK8 will provide differential GPS solutions when valid correction data is available. If a set of differentially correctable satellites cannot be found which meets the satellite mask settings, the receiver will transition to output standard GPS solutions. The Lassen-SK8 automatically switches between DGPS and standard GPS based on the availability of valid correction data.

4-6 Lassen-SK8 Embedded GPS Module

4.5.4 Differential GPS Operation

The Lassen-SK8 is capable of accepting and decoding RTCM SC-104 data. RTCM SC104 is an industry standard protocol for differential correction data. The Lassen-SK8 is configured to accept RTCM SC-104 correction data over Port 2 (J4, pin 7). Alternatively, you can use TSIP packets 60 and 61 or the TAIP and DD messages to input differential corrections through the primary serial port (J4, pin 5).

4.6 Position Accuracy

GPS position accuracy is degraded by atmospheric distortion, satellite and receiver clock errors, and Selective Availability (SA). Effective models for atmospheric distortion of satellite signals have been developed to minimize the impact of tropospheric and ionospheric effects. The impact of satellite clock errors is minimized by incorporating the clock corrections transmitted by each satellite used in the position solution. SA is the most significant contributor to position error and cannot be effectively combated except with differential GPS.

4.6.1 Selective Availability (SA)

Operation and Performance

The U.S. Department of Defense, through a program called Selective Availability, intentionally degrades GPS accuracy for civilian users. The SA program creates position errors by modifying the apparent position of each satellite and introducing random dither into each satellite's clock.

In extreme cases all sources of error (natural, PDOP, and SA) can combine to produce large position errors. The DOD's definition of accuracy under SA is 100 meters 2 dRMS (horizontal 2 dimensional, 95% of the time). In April 1996, the U.S. government approved plans for disabling SA.

4.6.2 Differential GPS (DGPS)

Differential GPS is an effective technique for overcoming the effects of SA and other sources of position error. DGPS relies on GPS error corrections transmitted by a reference station placed at a known location. The reference station compares its GPS position solution to its precisely surveyed position and calculates the error in each satellite's range measurement. The industry standard protocol for GPS correction data is RTCM SC-104.

The GPS corrections are broadcast to mobile GPS receivers in neighboring areas. The mobile receivers incorporate the GPS corrections in their position solution to achieve excellent accuracy. For marine applications, corrections are typically modulated on marine radio beacon broadcasts. For land-based applications, the correction data can be transmitted over FM sub-carrier, cellular telephone or dedicated UHF or VHF radio links.

DGPS can reduce position error to under 5 meters, 95% of the time under steady state conditions. The DGPS accuracy is highly dependent on the quality and age of the differential corrections and the proximity of the mobile receiver to the reference site.

Lassen-SK8 Embedded GPS Module 4-7

Operation and Performance

4.7 Coordinate Systems

Once the Lassen-SK8 achieves its first fix, it is ready to commence output of position, velocity, and time information.

This information is output over serial communication channel in either the TSIP, TAIP, or NMEA protocol, as determined by the settings of the receiver. These protocols are defined in the following Appendices:

• TSIP - Appendix A

• TAIP - Appendix C

• NMEA - Appendix E

To change from one protocol to another, please see “Configuring your Receiver” in Appendix A.

4.7.1 TSIP Coordinate Systems

TSIP has the widest choice of coordinate systems. The output format is chosen by TSIP command 0x35. The output formats include the following:

• LLA position — Latitude, longitude, altitude (LLA) according to the WGS ellipsoid or one of over a hundred other datums. See Appendix A, Table A-86 for a list of available datums. Altitude can be chosen to be height above ellipsoid (HAE) or height above mean sea level (MSL).

• ENU velocity — ENU velocity is the velocity in East, North, and Up coordinates. These coordinates are easily converted to speed and heading.

• ECEF position and velocity — ECFF position and velocity is Earth-Centered, Earth-Fixed frame is a Cartesian coordinate frame with its center at the earth's center, the z-axis through the North Pole, and the x-axis through longitude 0 degrees, latitude 0 degrees. Velocity is reported relative to the same axes.

• UTM — Universal Transverse Mercator (UTM) is a mapping coordinate system used by many government agencies.

There are also two time coordinate systems:

• GPS time — GPS time is determined by an ensemble of atomic clocks operated by the Department of Defense (DOD).

• UTC time — UTC time is the world standard maintained by an ensemble of atomic clocks operated by government organizations around the world.

GPS time is steered relative to Universal Coordinated Time (UTC). GPS does not recognize leap seconds resulting in a situation where GPS time is currently 12 seconds ahead of UTC time. Time tags for most output messages can be in either UTC time or GPS time, as chosen by TSIP command 0x35.

4-8 Lassen-SK8 Embedded GPS Module

4.7.2 NMEA 0183

The NMEA 0183 protocol only supports LLA format and UTC time. Velocity is always described as horizontal speed and heading; vertical speed is not output.

4.7.3 TAIP

The TAIP protocol only supports LLA position output. Timetags are GPS, except for the TM time mark message.

4.8 Performance Characteristics

4.8.1 Update Rate

The Lassen-SK8 computes and outputs position solutions once per second, on the second. NMEA outputs can be scheduled at a slower rate using TSIP command 7Ah. Refer to Appendix A.

Operation and Performance

4.8.2 Dynamic Limits

The dynamic operating limits for the Lassen-SK8 are listed below. These operating limits assume that the GPS module is correctly embedded and that the overall system is designed to operate under the same dynamic conditions.

Table 4-2. Lassen-SK8 Operating Limits

Operation Limit

Acceleration 4 g (39.2 m/s2) Jerk 20 m/s Speed 500 m/s Altitude 18,000 m

4.8.3 Re-Acquisition

Re-acquisition time for a momentary signal blockages is typically under 2 seconds. When a satellite signal is momentarily interrupted during normal operation, the receiver

continues to search for the lost signal at the satellite's last known Doppler frequency. If the signal is available again within 15 seconds, the receiver will normally re-establish track within two seconds. If the lost signal is not re-acquired within 15 seconds, the receiver initiates a broader frequency search. The receiver will continue to search for the satellite until it falls below the elevation mask.

Lassen-SK8 Embedded GPS Module 4-9

Operation and Performance

4.9 GPS Timing

In many timing applications, such as time/frequency standards, site synchronization systems and event measurement systems, GPS receivers are used to discipline local oscillators.

The GPS constellation consists of 24 orbiting satellites. Each GPS satellite contains a highly-stable atomic (Cesium) clock, which is continuously monitored and corrected by the GPS control segment. Consequently, the GPS constellation can be considered a set of 24 orbiting clocks with worldwide 24-hour coverage.

GPS receivers use the signals from these GPS “clocks” to correct its internal clock, which is not as stable or accurate as the GPS atomic clocks. GPS receivers like the Lassen-SK8 output a highly accurate timing pulse (PPS) generated by its internal clock, which is constantly corrected using the GPS clocks. This timing pulse is synchronized to UTC within ±500 ns.

In addition to serving as a highly accurate stand-alone time source, GPS receivers are used to synchronize distant clocks in communication or data networks. This synchronization is possible since all GPS satellite clocks are corrected to a common master clock. Therefore, the relative clock error is the same, regardless of which satellite or satellites are used. For timing applications requiring a “common clock”, GPS is the ideal solution.

GPS time accuracy is bounded by the same major source of error affecting position accuracy, Selective Availability. The position and time errors are related by the speed of light. Therefore, a position error of 100 meters corresponds to a time error of approximately 333 ns. The hardware and software implementation affects the GPS receiver's PPS accuracy level. The receiver's clocking rate determines the PPS steering resolution.

The Lassen-SK8 clocking rate is 3.126 MHz. This rate corresponds to a steering resolution of ±160 ns. Software techniques such as over-determined clock algorithm can achieve PPS accuracy greater than Selective Availability because more satellites are used to give a higher timing accuracy.

4.9.1 Serial Time Output

Both the TSIP, TAIP, and NMEA protocols include time messages. Refer to Report Packet 41 in Appendix A or the ZDA descriptions in Appendix D for a description of the time reports for each protocol and the TAIP TM message.

Note – GPS time differs from UTC (Universal Coordinated Time) by a variable, integer number of seconds UTC = (GPS time) - (GPS / UTC offset).

As of June 1997, the GPS / UTC offset was 11 seconds. The offset has historically increased by 1 second about every 18 months. System designers should plan to read the offset value as a part of the timing interface to obtain UTC. The GPS week number is in reference to a base week (Week #0), starting January 6, 1980.

4-10 Lassen-SK8 Embedded GPS Module

4.9.2 Timing Pulse Output (PPS)

A pulse-per-second (PPS), ten microsecond wide pulse is available on the Lassen-SK8 8-pin interface connector. The pulse is sent once per second and the rising edge of the pulse is synchronized with UTC. The pulse shape is affected by the distributed capacitance of the attached cabling and input circuit. The rising edge is typically less than 20 ns wide. The falling edge should never be used for timing applications.

Operation and Performance

Note – The PPS signal output by the Lassen-SK8 is a CMOS/TTL level signal. If this signal must be furnished to a remote location, the system designer should provide an RS422 driver for the timing pulse.

When the Lassen-SK8 is installed on the interface motherboard (supplied in the Starter Kit), the PPS signal is connected to an open collector circuit and the polarity of the signal is inverted.

4.10 System Architecture

The Lassen-SK8 module (see Figure 4-1) uses eight processing channels operating on the L1 frequency of 1575.42 MHz and using the coarse acquisition (C/A) code. The module uses custom integrated circuitry designed by Trimble to track the GPS satellite signals. These ICs also contain support circuitry to the navigation processor. An integrated 32-bit microprocessor is used for tracking, computing a position, and performing the I/O operations.

The module receives the GPS satellite signals through the antenna feed line connector, amplifies the signals, and then passes them to the RF down converter. A highly stable crystal reference oscillator operating at 12.504 MHz is used by the down converter to produce the signals used by the 8-channel signal processor. The 8-channel signal processor tracks the GPS satellite signals and extracts the carrier code information as well as the navigation data at 50 bits per second.

Operation of the tracking channels is controlled by the navigation processor. The tracking channels are used to track the highest eight satellites above the horizon. The navigation processor will then use the optimum satellite combination to compute a position. The navigation processor also manages the ephemeris and almanac data for all of the satellites, and performs the data I/O.

Lassen-SK8 Embedded GPS Module 4-11

Operation and Performance

RF IN

From Active antenna (20 to 40 db gain)

Ant. Pwr Protect/ Detect

Band Pass

Filter

IF Filter

SCOTT

RF/IF

CUSTOM

ROM

4Mb

Base Band

Filter

SClock

12.504 MHz

I Q

TTLTTL

8 CHANNEL

GPS DSP

12.504 MHz Oscillator

12.5 MHz TTL

SCORPION CUSTOM IC

DUART

Calibration

Port A Port B

RAM 1 Mb

Prime Power

PWR MON

Backup Power

SK8 Functional Block Diagram

sk8fbd.dwg 12/28/95

Figure 4-1. Lassen-SK8 Block Diagram

RTC

RESET CONTROL

32 BIT

CPU

SEE

A/D, D/A, PWM

32.768KHz Crystal

1 PPS

4-12 Lassen-SK8 Embedded GPS Module

A Trimble Standard Interface

Protocol

The Trimble Standard Interface Protocol (TSIP) provides the system designer with over 75 commands that may be used to configure a GPS receiver for optimum performance in a variety of applications. TSIP enables the system designer to customize the configuration of a GPS module to meet the requirements of a specific application.

This appendix provides the information needed to make judicious use of the powerful features TSIP has to offer, to greatly enhance overall system performance and to reduce the total development time. The reference tables beginning on Page 2 will help you determine which packets apply to your application. For those applications requiring customizing, see Page 3 for a detailed description of the key setup parameters. Application guidelines are provided for each TSIP Command Packet, beginning on Page 20.

A.1 Interface Scope

The Trimble Standard Interface Protocol is used in Trimble 6-channel and 8-channel receiver designs. The protocol was originally created for the Trimble Advanced Navigation Sensor (TANS) and is colloquially known as the TANS protocol even though the protocol applies to many other devices.

The Lassen-SK8 has two independently configurable serial I/O communication ports. Port1 is a bi-directional control and data port utilizing a Trimble Standard Interface Protocol (TSIP) or Trimble ASCII Interface Protocol (TAIP). Port 2 is a bi-directional port used to receive differential GPS (DGPS) corrections in the industry standard RTCMSC-104 format and for output of industry standard ASCII NMEA sentences. Port 1 can also be configured to TAIP I/O using the TSIP command. The dual data I/O port characteristics and other options are user programmable and stored in non-volatile memory.

The TSIP protocol is based on the transmission of packets of information between the user equipment and the unit. Each packet includes an identification code (1 byte, representing 2 hexadecimal digits) that identifies the meaning and format of the data that follows. Each packet begins and ends with control characters.

Lassen-SK8 Embedded GPS Module A-1

Trimble Standard Interface Protocol

This document describes in detail the format of the transmitted data, the packet identification codes, and all available information over the output channel to allow the user to choose the data required for his particular application. As will be discussed, the receiver transmits some of the information (position and velocity solutions, etc.) automatically when it is available, while other information is transmitted only on request. Additional packets may be defined for particular products and these will be covered in the specifications for those products as necessary.

The TSIPCHAT utility, part of the GPS Tool Kit, is designed to exercise many of the TSIP packets. The GPSSK Utility, part of the GPS Took Kit, is designed to exercise many of the TSIP messages.

A.2 Automatic Output Packets

The Lassen-SK8 receiver module is configured to automatically output the following packets. For minimal system implementations, these output packets provide all of the information required for operation including time, position, velocity, and receiver and satellite status and health. Position and velocity are reported using one or more of the packets listed below, depending on the selected I/O options. While there are other packets automatically output, the following packets provide the information most commonly used. No input packets are required.

‘

Table A-1. Automatic Output Packets

Reporting

Output Packet ID Description

0x41 GPS time 5 seconds 0x42, 0x83, 0x4A,

0x84, 0x43, 0x56, 0x8F-17, 0x8F-18, 0x8F-20

0x43, 0x56, 0x8F-20 velocity (choose packet with I/O options) 1 second 0x46 health of receiver 5 seconds 0x4B machinecode/status (includes antenna

0x6D all-in-view satellite selection 1 second 0x82 DGPS position fix mode (only in DGPS

Note – See page A-16 for a detailed description of the key receiver setup parameters.

position (choose packet with I/O options) 1 second

fault detect)

mode)

Interval

5 seconds

1 second

A-2 Lassen-SK8 Embedded GPS Module

A.3 Customizing Receiver Operations

To customize the Lassen-SK8 receiver output for your application:

1. Set up the receiver using TSIP commands until the receiver operation is as desired

2. Use command 0x8E-26 to store the settings in non-volatile memory

These settings will control receiver operation whenever the receiver is cold-started, or when battery back-up is lost. Table A-2 shows all of the commands that can be stored in SEEPROM.

A.3.1 TAIP Customizing

To customize the receiver for TAIP on either Port 1 or Port 2, use command 0x8E-40 which sets the TAIP default settings. Then use command 0xBC to change port baud settings and set the language to TAIP.

.If Port 1 is used, TSIP communication will stop so, use TAIP command RT, specifically:

>SRTSAVE_CONFIG<

to store to non-volatile memory instead of 0x8E-26 settings.

Trimble Standard Interface Protocol

A.3.2 NMEA Customizing

To customize the NMEA output on Port 2, use the command 0x7A

A.3.3 Reconfiguring to Factory Default Settings

To reset the receiver configuration to factory default settings, use TSIP command 0x1E with data byte-F. This will negate all previous 0x8E-26 settings.

Caution – Whenever using command 0x8E-26 or 0x1E, wait two seconds before removing power. This allows the process of writing to non-volatile memory to be completed.

Warning – When changing port settings, record the new settings for future reference. These settings must be used whenever the receiver is powered up. If the port settings are lost, use theTPRESET program in the Toolkit disk to return the board to the factory default settings.

Lassen-SK8 Embedded GPS Module A-3

Trimble Standard Interface Protocol

Table A-2. Customizing Receiver Operation I/Os

Input ID Description Output ID

0xBB set/request query receiver configuration BB 0xBC set/request query port configuration BC 0x35 set input/output options 55 0x70 enable/disable PV/altitude filters 70 0x7A set NMEA schedule 7B 0x8E-15 set datums 8F-15 0x8E-19 enable UTM 8F-19 0x8E-20 enable superpacket 0x8E-26 save settings

Note – After setting wait 2 seconds.

A-4 Lassen-SK8 Embedded GPS Module

A.4 Automatic Position and Velocity Reports

The receiver automatically outputs position and velocity reports at set intervals. Automatic report packets are controlled by Packet 35. Setting the control bits as indicated in the table below allows you to control which position and velocity packets are output.

Table A-3. Automatic Position and Velocity Reports Control Setting Bits

Trimble Standard Interface Protocol

Packet ID Description

0x42 single

precision XYZ position

0x83 double-

precision XYZ position

0x4A single-

precision LLA position

0x84 double-

precision LLA position

0x43 velocity fix

(XYZ, ECEF)

0x56 velocity fix

(ENU)

0x8F-17 Single

Precision

0x8F-18 Single

Precision ELEF

0x8F-20 LLA & ENU 1

Byte 0 Bit 0

1 0

1 1

Byte 0 Bit 1

1 0

1 1

Byte 0 Bit 4

0 1

Byte 0 Bit 5

Byte 1 Bit 0

Byte 1 Bit 1

Lassen-SK8 Embedded GPS Module A-5

Trimble Standard Interface Protocol

A.5 Warm Start Packets

If the receiver is connected to a back-up power source such as a lithium battery, the data required to cause a warm start is retained even when main power is turned off. Before power off, check the following automatic outputs to ensure a warm start will occur on the next power on cycle:

• The value of Packet 0x4B (byte 1, bit 3) is 0 which indicates that the almanac is complete and current.

• The position input (0x42,4A, 0x83, 0x84, 0x8F-17, 0x8F-18, 0x8F-20) are correct. See Table A-4.

• The time in Packet 41 is correct.

• Turning on main power will cause a warm start.

If however you are not supplying the receiver with battery power when main power is off, you can still warm start the receiver by sending the following commands after the receiver has completed its internal initialization and has sent Packet 82 (see Table A-5).

Table A-4. Warm Start Packet Commands

INPUT Description

0x2B initial position 0x2E initial time 0x38-02 almanac (for each SV) 0x38-03 almanac health 0x38-04 ionosphere page 0x38-05 UTC correction

A-6 Lassen-SK8 Embedded GPS Module

A.6 Packets Output at Power-Up

The following table lists the messages output by the receiver at power-up. After completing its self-diagnostics, the receiver automatically outputs a series of packets which indicate the initial operating condition of the receiver. Messages are output in the following order. After Packet 82 is output, the sequence is complete and the receiver is ready to accept commands.

Table A-5. Packet Power-up Output Messages

Output ID Description Notes

0x41 GPS time This Packet is only output

0x45 software version -0x46 receiver health -0x4B machine code/status -As chosen, see Table A-4 position/Velocity output As chosen, see Table A-

82 DGPS position fix mode --

Trimble Standard Interface Protocol

if GPS time is available.

A.7 Differential GPS Packets

For differential GPS applications you may need to implement the following TSIP control commands.

Table A-6. Differential GPS Packet TSIP Control Commands

Input ID Description Output ID

0xBC Port configuration 0xBC 0x60 Differential GPS corrections (types 1 and 9) -0x61 Differential GPS corrections (type 2) -0xBB Differential Auto or Manual operating mode. Maximum

age that differential corrections will be used

0x65 Differential correction data request 0x85

0xBB

Lassen-SK8 Embedded GPS Module A-7

Trimble Standard Interface Protocol

A.8 Timing Packets

If you are using the Lassen-SK8 as a timing system, you may need to implement the following TSIP control commands.

Table A-7. Timing Packet TSIP Control Commands

Input ID Description Output ID

0x21 get the current GPS time. 0x41 0xBB setup static mode if desired. 0xBB 0x38-05 request UTC parameters. 0x58-05

A.9 Satellite Data Packets

The following packets contain a variety of GPS satellite data.

Table A-8. Satellite Date Packet Data I/O Descriptions

Input ID Description Output ID

0x27 request signal levels 0x47 0x28 request GPS system message 0x48 0x38 request/load satellite system data 0x58 0x39 set/request satellite disable or ignore health 0x59 0x3A/auto request last raw measurement 0x5A 0x3C request tracking status 0x5C auto Synchronized Measurement measurement packet 0x6F

A.10 Background Packets

The receiver automatically outputs a set of packets that the user may want to monitor for changes in receiver operations. These messages are output at the rates indicated in the table below.

Table A-9. Background Packet Output Messages

Output ID Description Notes

0x41 GPS time If the receiver's GPS clock is set and the

0x46, 0x4B receiver health messages Receiver health messages are output

0x6D mode packets Mode packets are output every second.

receiver is not outputting positions, time is output approximately every 5 seconds.

every 5 seconds.

A-8 Lassen-SK8 Embedded GPS Module

Trimble Standard Interface Protocol

A.11 Backwards Incompatibility of Lassen-SK8 Packets with Previous

TSIP Versions

Several new TSIP command packets have been made available with the release of the Lassen-SK8 receiver module, and some existing packets have been modified or are no longer supported. Table A-10 identifies the backwards compatibility of auto-output packets. Table A-11 identifies the backwards compatibility of the TSIP command packets. Unless otherwise noted, the commands and their corresponding output packets are still supported in the firmware.

Table A-10. Supported Auto-Output Packet Command Backward

Compatibility

Old Packet Control New Packet Control Notes

0x40 auto 0x58-02 0x38-02 no longer auto 0x44 auto 0x6D 0x38-06 0x44 not supported 0x5A auto 0x6F auto 0x5B auto 0x58-06 no longer auto 0x5E auto 0x5E not supported 0x8F-01,

0x8F-02

auto 0x8F-20 auto 0x01, 0x02 not

supported

Lassen-SK8 Embedded GPS Module A-9

Trimble Standard Interface Protocol

A-10 Lassen-SK8 Embedded GPS Module

A.12 Recommended TSIP Packets

Table A-11. Recommended TSIP Packet Data

Function Description Input Output

Protocol and port setup set/query port configuration 0xBC 0xBC

set/query NMEA configuration 0x7A 0x7B set/query I/O options

(autoreport and format options) Packet output control 0x6E-01 0x6E-01

Navigation GPS time 0x21 0x41

position & velocity (superpacket) 0x8E-20

double-precision LLA 0x37/auto 0x84 double-precision XYZ 0x37/auto 0x83 ENU velocity 0x37/auto 0x56 XYZ velocity 0x37/auto 0x43

Satellite and tracking information

Receiver settings query software version 0x1F 0x45

DGPS query DGPS corrections 0x65 0x85

query receiver state (health) 0x26 0x46, 0x4B

query current satellite selection 0x24 0x6D query signal levels 0x27 0x47 query satellite information

(azimuth, elevation, etc.) Synchronized Measurement

packet

set/query datum values 0x8E-15 0x8F-15 query receiver ID & error status 0x26 0x4B, 0x46 set/query satellite flags 0x39 0x59 set/query receiver configuration 0xBB 0xBB set altitude for 2D mode 0x2A 0x4A disable PV/altitude filters 0x70 0x70 set/query positioning mode (2D

v. 3D)

query DGPS operating mode & status

load DGPS Type 1 correction 0x60 load DGPS Type 2 correction 0x61

Trimble Standard Interface Protocol

0x35 0x55

0x8F-20 or 0x37 or auto

0x3C 0x5C

0x6F

0xBB 0xBB

0x62 0x82

Lassen-SK8 Embedded GPS Module A-11

Trimble Standard Interface Protocol

Table A-11. Recommended TSIP Packet Data (Continued)

Function Description Input Output

GPS system query/load GPS system data 0x38 0x58

Initialization full reset (clear battery backup

GPS system message 0x28 0x48

0x1E

and/or non-volatile settings) soft reset 0x25 set GPS time 0x2E 0x4E set exact LLA 0x32 set approx. XYZ 0x23 set approx. LLA 0x2B set exact XYZ 0x31

A-12 Lassen-SK8 Embedded GPS Module

A.13 Command Packets Sent to the Receiver

The table below summarizes the command packets sent to the receiver. The table includes the input Packet ID, a short description of each packet, and the associated response packet. In some cases, the response packets depend on user-selected options. These selections are covered in the packet descriptions beginning on page A-13.

Table A-12. User-Selected Command Packet Options

Input ID Packet Description Output ID

0x1E clear battery back-up/reset See Note 1 0x1F software version 0x45 0x21 current time 0x41 0x23 initial position (XYZ ECEF) -0x24 request receiver position fix mode 0x6D 0x25 soft reset & self-test See Note 1 0x26 receiver health 0x46, 0x4B 0x27 signal levels 0x47 0x28 GPS system message 0x48 0x2A altitude for 2-D mode 0x4A 0x2B initial position (Lat, Lon, Alt) -0x2D oscillator offset 0x4D 0x2E set GPS time 0x4E 0x31 accurate initial position (XYZ Cartesian ECEF) -0x32 accurate initial position -0x35 I/O options 0x55 0x37 status and values of last position and velocity 0x57 0x38 load or request satellite system data 0x58 0x39 satellite disable 0x59 0x3A last raw measurement 0x5A, see Note 2 0x3C tracking status 0x5C, see Note 2 0x60 type 1 differential correction -0x61 set differential correction -0x62 request differential GPS position fix mode 0x82 0x65 differential correction status 0x85, see Note 2 0x6E Synchronized Measurement output control 0x6E 0x70 filter configuration 0x70 0x7A set/request NMEA output configuration 0x7B 0xBB set receiver configuration 0xBB 0xBC set port configuration 0xBB

Trimble Standard Interface Protocol

Lassen-SK8 Embedded GPS Module A-13

Trimble Standard Interface Protocol

Table A-12. User-Selected Command Packet Options (Continued)

Input ID Packet Description Output ID

0x8E-15 set/request current datum values 0x8F-15 0x8E-20 last fix with extra information (fixed point) 0x8F-20

Note 1. – Output is determined by Packet 0x35 settings. See Table A-5 to determine which messages are output at power-up.

Note 2. – No response sent if data is not available.

Note 3. – Not all Packet 0x39 operations have a response. See Packet 0x39 description.

A-14 Lassen-SK8 Embedded GPS Module

Trimble Standard Interface Protocol

A.14 Report Packets Sent by the GPS Receiver to the User

The table below summarizes the packets output by the receiver. The table includes the output Packet ID, a short description of each packet, and the associated input packet. In some cases, the response packets depend on user-selected options. These selections are covered in the packet descriptions beginning on page A-23.

Table A-13. User-Selected Report Packet Options

Output ID Packet Description Input ID

0x41 GPS time 0x21, auto 0x42 single-precision XYZ position 0x25, 0x37, auto 0x43 velocity fix (XYZ ECEF) 0x37, auto 0x45 software version information 0x1F, power-up 0x46 health of Receiver 0x26, auto, power-up 0x47 signal level for all satellites 0x27 0x48 GPS system message 0x28 0x4A single-precision LLA position 0x37, auto 0x4B machine code/status 0x26, auto, power-up 0x4D oscillator offset 0x2D 0x4E response to set GPS time 0x2E 0x55 I/O options 0x35 0x6E Synchronized Measurement packet output

control 0x6F Synchronized Measurement packet Auto 0x56 velocity fix (ENU) 0x37, auto 0x57 information about last computed fix 0x37 0x58 GPS system data/acknowledge 0x38 0x59 sat enable/disable & health heed 0x39 0x5A raw measurement data 0x3A 0x5C satellite tracking status 0x3C 0x6D all-in-view satellite selection 0x24, auto 0x82 differential position fix mode 0x62, auto 0x83 double-precision XYZ auto, 0x37 0x84 double-precision LLA auto, 0x37 0x85 differential correction status 0x65 0x8F-20 last fix with extra information (fixed point) auto, 0x37, 0x8E-20 0x8F-17 UTM auto, 0x37

Lassen-SK8 Embedded GPS Module A-15

Trimble Standard Interface Protocol

A.15 Key Setup Parameters or Packet BB

Selecting the correct operating parameters has significant impact on receiver performance. Packet 0xBB (set receiver configuration) controls the key setup parameters.

The default operating parameters allow the receiver to perform well in almost any environment. The user can optimize the receiver to a particular application if the vehicle dynamics and expected level of obscuration are understood. If the receiver is then taken out of this environment, the specifically tuned receiver may not operate as well as a receiver with the default options.

The table below lists suggested parameter selections as a function of obscuration and whether accuracy or fix density is important. In this table, NA indicates that the operating parameter is not applicable, DC (don't care) indicates that the user may choose the operating parameter.

Table A-14. Setup Parameters

Packet Parameter Accuracy Fixes

0xBB Fix mode Man 3D AUTO AUTO 0xBB Dynamics code Land Land Land 0xBB Elevation mask 10° 5° 5° 0xBB Signal mask 6.0 4.0 2.0 0xBB DOP mask 6.0 12.0 12.0 0xBB DOP switch NA 8.0 5.0 0xBB DGPS correction age 10 Seconds N/A 30 Seconds

Factory Default

The default values in Table A-15 allow the receiver to operate well under the most varied and demanding conditions. A user may choose to change the default parameters if the receiver is only required to perform in a specific or limited environment. The user should be warned that when the receiver is exposed to operating conditions which are different from the conditions described by the user setup, then the performance may be degraded.

Initially, the user must consider the environment in which the receiver is expected to operate. There is a trade-off between how frequently a position fix is output versus the absolute accuracy of the fix. The user must decide which takes priority and then make the appropriate selections. This becomes increasingly important when frequent satellite blockages are expected, as in downtown “urban canyon” environments and heavily foliated areas.

Following is a description of the key fields in Packet 0xBB.

A-16 Lassen-SK8 Embedded GPS Module

A.15.1 Packet 0xBB - Set Fix Mode

Packet 0xBB is used to choose the appropriate position fix mode for your application: 2-D, 3-D or AUTO. The default mode is AUTO 2-D/3-D, where the receiver first attempts to obtain a 3-D solution with a PDOP below both the DOP mask and DOP switch. If this is not possible, then the receiver attempts to obtain a 2-D solution with a DOP less than the DOP mask. This mode supplies fairly continuous position fixes even when there is frequent obscuration. This mode is preferable for most land or air applications, where altitude changes are occurring and there is occasional obscuration.

The highest accuracy fix mode is 3-D manual, where altitude is always calculated along with the latitude, longitude, and time. However, this requires four satellites with a PDOP below the DOP mask set in Packet BB in order to obtain a position. Normally, this will provide the most accurate solution. Thus, if only 3-D solutions are desired, then the user should request 3-D manual mode. Depending on how the PDOP mask is set, this may be restrictive when the receiver is subjected to frequent obscuration, or when the geometry is poor due to an incomplete constellation.

Alternatively, if the user only wants a 2-D solution, then 2-D manual should be requested. In this case, the receiver uses either the last altitude obtained in a 3-D fix, or the altitude supplied by the user. However, any error in the assumed altitude will affect the accuracy of the latitude and longitude solution.

Trimble Standard Interface Protocol

High accuracy users should avoid the 2-D mode and should expect fixes with accuracies which are at best as accurate as the supplied altitude. If a marine user enters sea-level as the altitude, then small errors in the horizontal solution will occur when the sea state is rough or there are high tidal variations. However, these errors may be smaller than the altitude errors induced by SA, so 2-D may be preferable for a marine user who does not want to observe “unusual” altitudes.

A.15.2 Dynamics Code

The feature default is LAND mode, where the receiver assumes a moderate dynamic environment. In this case, the satellite search and re-acquisition routines are optimized for vehicle type environments. In SEA mode, the search and re-acquisition routines assume a low acceleration environment and reverts to user entered altitude in 2-D auto. In AIR mode, the search and re-acquisition routines are optimized for high acceleration conditions.

A.15.3 Elevation Mask

This is the minimum elevation angle for satellites to be used in a solution output by the receiver. Satellites which are near the horizon are typically more difficult to track due to signal attenuation, and are also generally less accurate due to higher variability in the ionospheric and tropospheric corruption of the signal. When there are no obstructions, the receiver can generally track a satellite down to near the horizon. However, when this mask is set too low, the receiver may experience frequent constellation switching due to low elevation satellites being obscured.

Lassen-SK8 Embedded GPS Module A-17

Trimble Standard Interface Protocol

Frequent constellation switching is undesirable because position jumps may be experienced when SA is present and DGPS is not available to remove these effects. The benefit of a low elevation mask is that more satellites are available for use in a solution and a better PDOP may be yielded. The current mask is set to five degrees and provides a reasonable trade-off of the benefits and drawbacks. High accuracy users may prefer a mask angle around ten degrees, where the ionosphere and troposphere begin to be more predictable

A.15.4 Signal Level Mask

This mask defines the minimum signal strength for a satellite used in a solution. There is some internal hysteresis on this threshold which allows brief excursions below the threshold if lock is maintained and the signal was previously above the mask. The factory default mask has been set to zero. High accuracy users may use a slightly higher mask of

6.0-8.0, since weaker measurements may be slightly noisier and are often caused by reflected signals which provide erroneous ranges.

One should also resist the temptation to set the elevation and SNR masks too low. The satellite geometry is sometimes improved considerably by selecting low elevation satellites. They are, however, subject to significant signal degradation by the greater ionospheric and tropospheric attenuation that occurs. They are also subject to more obscuration by the passing scenery when the receiver is in a moving vehicle. The code phase data from those satellites is therefore more difficult to decode and therefore has more noise.

Note – A level of hysteresis in the signal level mask is allowed in the core operating software. The hysteresis allows the receiver to continue using satellite signals which fall slightly below the mask and prevents the receiver from incorporating a new signal until the signal level slightly exceeds the mask. This feature minimizes constellation changes caused by temporary fluctuations in signal levels.

A.15.5 DOP Mask and Switch

The DOP mask is the maximum DOP limit for any 2-D or 3-D position solution will be made. The DOP switch is the level at which the receiver stops attempting a 3-D solution, and tries for a 2-D solution when in automatic 2-D, 3-D mode. The switch level has no effect in either manual mode. Raising the DOP mask will generally increase the fix density during obscuration, but the fixes with the higher DOP will be less accurate (especially with SA present). Lowering the mask will improve the average accuracy at the risk of lowering the fix density.

A-18 Lassen-SK8 Embedded GPS Module

A.15.6 Packet 0xBB - Set DGPS Mode

Packet 0xBB is used to set the differential GPS operating mode. The factory default mode is OFF. If differential corrections are available, the recommended mode is DGPS Auto. In this mode, the receiver computes differentially corrected positions whenever valid corrections are available. Otherwise, the receiver computes non-differentially corrected positions.

In manual DGPS mode, the receiver only computes solutions if corrections are available for the selected satellites. This is the most accurate mode but it is also the most selective, since the fix density is dependent on the availability of corrections. The applicability of corrections is determined by the maximum age which can be set using Packet 0xBB.

The AUTO mode avoids the fix density problem but opens the possibility of going in and out of DGPS mode, potentially resulting in position and velocity jumps. In differential OFF mode, the receiver will not use corrections even if they are valid. If accuracy is critical, use MANUAL DGPS mode. If fix density is critical, AUTO DGPS is the recommended mode.

A.16 Packet Structure

Trimble Standard Interface Protocol

TSIP packet structure is the same for both commands and reports. The packet format is:

Where:

• <DLE> is the byte 0x10

• <ETX> is the byte 0x03

• <id> is a packet identifier byte, which can have any value excepting <ETX> and

<DLE>.

The bytes in the data string can have any value. To prevent confusion with the frame sequences <DLE> <id> and <DLE> <ETX>, every <DLE> byte in the data string is preceded by an extra <DLE> byte ('stuffing'). These extra <DLE> bytes must be added ('stuffed') before sending a packet and removed after receiving the packet. Notice that a simple

<DLE> <ETX> sequence does not necessarily signify the end of the packet, as these can be

bytes in the middle of a data string. The end of a packet is <ETX> preceded by an odd number of <DLE> bytes.

Multiple-byte numbers (integer, float, and double) follow the ANSI / IEEE Std. 754 IEEE Standard for binary Floating-Point Arithmetic. They are sent most-significant byte first. This may involve switching the order of the bytes as they are normally stored in Intel based machines. Specifically:

• INTEGER — A 16 bit unsigned number sent in two's complement format.

• SINGLE — Float, or 4 byte REAL has a precision of 24 significant bits, roughly

6.5 digits.

• DOUBLE — 8 byte REAL has a precision of 52 significant bits. It is a little better

than 15 digits.

Lassen-SK8 Embedded GPS Module A-19

Trimble Standard Interface Protocol

A.17 Packet Descriptions

A.17.1 Command Packet 0x1D

This packet commands the GPS receiver to set or clear the oscillator offset in batterybacked memory. This is normally used for servicing the unit.

To clear the oscillator offset, one data byte is sent: the ASCII letter 'C' = 0x43. To set the oscillator offset, four data bytes are sent: the oscillator offset in Hertz as a

Single real value.

A.17.2 Command Packet 0x1E

This packet commands the GPS receiver to clear all battery back-up data and to perform a software reset. This packet contains one data byte.

Caution – All almanac, ephemeris, current position, mode, and communication port setup information is lost by the execution of this command. In normal use this packet should not be sent. It is very helpful to keep a fresh copy of the current almanac, which is stored in the file GPSALM.DAT collected by the TSIPCHAT command “!”. This allows nearinstantaneous recuperation by the receiver in case of power loss or clearing of batterybacked memory by using the TSIPCHAT command “@” to load it back into the receiver memory.

Table A-15. Command Packet 0x1E Format

Byte Item Type Value Meaning

0 Reset

Mode

A.17.3 Command Packet 0x1F

This packet requests information about the version of software running in the Navigation and Signal Processors. This packet contains no data. The GPS receiver returns Packet

0x45.

BYTE 0x46

ASCII “F”

0x4B Erase BBRAM and Reset

Erase BBRAM, reset nonvolatile memory to factory default, and restart

A.17.4 Command Packet 0x21

This packet requests current GPS time. This packet contains no data. The GPS receiver returns Packet 0x41.

A-20 Lassen-SK8 Embedded GPS Module

A.17.5 Command Packet 0x23

This packet provides the GPS receiver with an approximate initial position in XYZ coordinates. This packet is useful if the user has moved more than a 1,000 miles after the previous fix. (Note that the GPS receiver can initialize itself without any data from the user; this packet merely reduces the time required for initialization.) This packet is ignored if the receiver is already calculating positions. The data format is shown below.

To initialize with latitude-longitude-altitude, use Command Packet 0x2B.

Table A-16 Command Packet 0x23 Data Format

Byte Item Type Units

0-3 X Single Meters 4-7 Y Single Meters 8-11 Z Single Meters

A.17.6 Command Packet 0x24

This packet requests current position fix mode of the GPS receiver. This packet contains no data. The GPS receiver returns Packet 0x6D.

Trimble Standard Interface Protocol

A.17.7 Command Packet 0x25

This packet commands the GPS receiver to perform a software reset. This is equivalent to cycling the power. The GPS receiver performs a self-test as part of the reset operation. This packet contains no data. Following completion of the reset, the receiver will output the start-up messages (see Table A-5). The GPS receiver sends Packet 0x45 only on power-up and reset (or on request); thus if Packet 0x45 appears unrequested, then either the GPS receiver power was cycled or the GPS receiver was reset.

A.17.8 Command Packet 0x26

This packet requests health and status information from the GPS receiver. This packet contains no data. The GPS receiver returns packet0x 46 and 0x4B.

A.17.9 Command Packet 0x27

This packet requests signal levels for all satellites currently being tracked. This packet contains no data. The GPS receiver returns Packet 0x47.

A.17.10 Command Packet 0x28

This packet requests the most recent GPS system ASCII message sent with the navigation data by each satellite. This packet contains no data. The GPS receiver returns Packet 0x48.

Lassen-SK8 Embedded GPS Module A-21

Trimble Standard Interface Protocol

A.17.11 Command Packet 0x2A

Note – This packet sets or requests the altitude parameters used for the Manual 2-D mode: Reference Altitude and Altitude Flag. Packet 0x4A (type 2) is returned.

Reference Altitude is the altitude used for manual 2-D positions if the altitude flag is set. Altitude is in units of HAE WGS-84 or MSL depending on the selected I/O options for the position. The Altitude Flag determines whether or not the Reference Altitude will be used. If set, it will be used. If cleared, altitude hold (last 3-D altitude) is used.

Note – With no data bytes, this packet requests the current values of these altitude parameters. In this case, the GPS receiver returns Packet 4A.

Table A-17. Packet 0x2A Set Altitude Only Description

Byte Item Type Meaning

0-3 Altitude SINGLE Reference altitude for 2-D

Note – Sets the Altitude Flag.

Table A-18. Reset Altitude Flag Description

Byte Item Type Value Meaning

0 Altitude Flag BYTE 0 x 00 Clear Altitude flag

A-22 Lassen-SK8 Embedded GPS Module

A.17.12 Command Packet 0x2B

This packet provides the GPS receiver with an approximate initial position in latitude and longitude coordinates (WGS-84). This packet is useful if the user has moved more than 1,000 miles after the previous fix. (Note that the GPS receiver can initialize itself without any data from the user; this packet merely reduces the time required for initialization.) This packet is ignored if the receiver is already calculating positions. To initialize with ELEF position, use Command Packet 0x23. The data format is shown inTable A-19:

Table A-19. Command Packet 0x23 Data Format

Byte Item Type Units

0-3 Latitude Single Radians, north 4-7 Longitude Single Radians, east 8-11 Altitude Single Meters

A.17.13 Command Packet 0x2D

This packet requests the calculated offset of the GPS receiver master oscillator. This packet contains no data. The GPS receiver returns Packet 0x4D. This packet is used mainly for service. The permissible oscillator offset varies with the particular GPS receiver unit.

Trimble Standard Interface Protocol

A.17.14 Command Packet 0x2E

This packet provides the approximate GPS time of week and the week number to the GPS receiver. The GPS receiver returns Packet 0x4E. The data format is shown below. The GPS week number reference is Week # 0 starting January 6, 1980. The seconds count begins at the midnight which begins each Sunday morning. This packet is usually not required when the battery back-up voltage is applied as the internal clock keeps time to sufficient accuracy. This packet is ignored if the receiver has already calculated the time from tracking a GPS satellite.

Note – See A.17.22, Report Packet 41 for information on the Extended GPS week number.

Table A-20. Command Packet 0x2E Data Formats

Byte Item Type Units

0-3 GPS time of week Single Seconds 4-5 Extended GPS week

Integer Weeks

number

Lassen-SK8 Embedded GPS Module A-23

Trimble Standard Interface Protocol

A.17.15 Command Packet 0x31

This packet is identical in content to Packet 0x23. This packet provides an initial position to the GPS receiver in XYZ coordinates. However, the GPS receiver assumes the position provided in this packet to be accurate. This packet is used for satellite acquisition aiding in systems where another source of position is available and in time transfer (one-satellite mode) applications. For acquisition aiding, the position provided by the user to the GPS receiver in this packet should be accurate to a few kilometers. For high-accuracy time transfer, position should be accurate to a few meters.

A.17.16 Command Packet 0x32

This packet is identical in content to Packet 0x2B. This packet provides the GPS receiver with an approximate initial position in latitude, longitude, and altitude coordinates. However, the GPS receiver assumes the position provided in this packet to be accurate. This packet is used for satellite acquisition aiding in systems where another source of position is available and in time transfer (one-satellite mode) applications. For acquisition aiding, the position provided by the user to the GPS receiver in this packet should be accurate to a few kilometers. For high-accuracy time transfer, position should be accurate to a few meters.

A.17.17 Command Packet 0x35

This packet requests the current I/O option states and optionally allows the I/O option states to be set as desired.

To request the option states without changing them, the user sends the packet with no data bytes included. To change any option states, the user includes 4 data bytes with the values. The I/O options, their default states, and the byte values for all possible states are shown below. These option states are held in battery-backed memory and can be set into nonvolatile RAM (EEPROM) with the 0x8E-26 command. The GPS receiver returns Packet

0x55. See A.3 for information on saving the settings to non-volatile memory.

These abbreviations apply to the following table: ALT (Altitude), ECEF (Earth-centered, Earth-fixed), XYZ (Cartesian coordinates), LLA (latitude, longitude, altitude), HAE (height above ellipsoid), WGS-84 (Earth model (ellipsoid)), MSL geoid (mean sea level), and UTC (coordinated universal time).

A-24 Lassen-SK8 Embedded GPS Module

Trimble Standard Interface Protocol

Table A-21. Command Packets 0x35 and 0x55 Data Descriptions

Default

Parameter

Byte

Name

0 position 0 (LSB) 1 XYZ ECEF Output

0 position 5 0 0: output no Super

1 velocity 0 1 XYZ ECEF Output

Bit Position

Bit Value Option

0: off 1: on

1 0 LLA Output

0: off 1: on

2 0 LLA ALT Output

0: HAE (datum) 1: MSL geoid

3 0 ALT input

0: HAE (datum) 1: MSL geoid

4 0 Precision-of-position

output 0: Send single-precision packet 1: Send doubleprecision packet

Packets 1: output all enabled Super Packets

6-7 0 not used

0: off 1: on

1 0 ENU Output

0: off 1: on

2-7 0 not used

Associated Packet

0x42 or 0x83

0x4A or 0x84

0x4A or 0x84 0x8F-17 0x8F-18

0x2A

0x42/4A/8F17

0x83/84/8F18

0x8F-17, 0x8F-18 0x8F-20

0x43

0x56

Lassen-SK8 Embedded GPS Module A-25

Trimble Standard Interface Protocol

Table A-21. Command Packets 0x35 and 0x55 Data Descriptions

(Continued)

Parameter

Byte

2 timing 0 0 time type

3 Auxiliary PR

Name

meas.

Default Bit Position

1 0 reserved 2 0 reserved 3 0 reserved 4 0 reserved 5-7 0 not used 0 0: off 0x5A 1 0: raw 0: raw Pr’s in 5A

2 reserved 3 0: off

4-7 reserved

Bit

Value Option

0: GPS time 1: UTC

1: filtered PR’s in 5A

output dBHz instead of

1: on

AMU

Associated Packet

0x42, 0x43, 0x4A, 0x83, 0x84, 0x56, 0x8F-17, 0x8F-18

0x5A

0x5A, 0x5C, 0x47, 0x6F

Note – Automatic output of 5 A messages is supported in the Lassen-SK8 for backwards compatibility with older TSIP applications.

Note – See the associated superpacket output, described later in this appendix. Packet 8E must be used to specify which superpacket is to be output.

A.17.18 Command Packet 0x37

This packet requests information regarding the last position fix and is only used when the receiver is not automatically outputting positions. The GPS receiver returns the position/ velocity auto packets specified in the 0x35 message as well as message 0x57.

A-26 Lassen-SK8 Embedded GPS Module

A.17.19 Command Packet 0x38

This packet requests current satellite data (almanac, ephemeris, etc.) or permits loading initialization data from an external source (for example, by extracting initialization data from an operating GPS receiver unit via a data logger or computer and then using that data to initialize a second GPS receiver unit). The GPS receiver returns Packet 0x58. (Note that the GPS receiver can initialize itself without any data from the user; it merely requires more time.)

To request data without loading data, use only bytes 0 through 2; to load data, use all bytes. Before loading data, observe the caution notice below. The data formats are located in Report Packet 0 x 5B.

Table A-22. Command Packet 0x38 Data Formats

Byte Item Type Value Meaning

0 Operation Byte 1

1 Type of

data

2 Sat PRN# Byte 0

3 length (n) Byte number of bytes of data to be

4 to n+3 data n Bytes

Byte 1

2 3 4 5 6

1 - 32

Trimble Standard Interface Protocol

Request data from SVeeSix; Load data into SVeeSix

not used Almanac Health page, T_oa, WN_oa Ionosphere UTC Ephemeris; request only

data that is not satellite - ID specific satellite PRN number

loaded

Caution – Proper structure of satellite data is critical to SVeeSix operation. Requesting data is not hazardous; Loading data improperly is hazardous. Use this packet only with extreme caution. The data should not be modified in any way. It should only be retrieved and stored for later reload.

Note – Ephemeris can not be loaded into the receiver in Version 7.52.

Lassen-SK8 Embedded GPS Module A-27

Trimble Standard Interface Protocol

A.17.20 Command Packet 0x39

Normally the GPS receiver selects only healthy satellites (based on transmitted values in the ephemeris and almanac) which satisfy all mask values, for use in the position solution. This packet allows you to override the internal logic and force the receiver to either unconditionally disable a particular satellite or to ignore a bad health flag. The GPS receiver returns Packet 0x59 for operation modes 3 and 6 only.

It should be noted that when viewing the satellite disables list, the satellites are not numbered but are in numerical order. The disabled satellites are signified by a “1” and enabled satellites are signified by a “0”.

Table A-23. Command Packet 0x39 Data Formats

Byte Item Type Value Meaning

0 Operation Byte 1

1 Satellite # Byte 0

2 3

4 5 6

1 - 32

Enable for selection (default) Disable for selection Request enable - or - disable status of all 32 satellites Heed health on satellite (default) Ignore health on satellite Request heed - or - ignore health on all 32 satellites

all 32 satellites any one satellite PRN number

This information is not held in battery-backed memory. At power-on and after a reset the default values are set for all satellites.

Caution – Ignoring satellite health flags can cause the GPS receiver software to lock up. An unhealthy satellite may contain defective data. Use extreme caution when ignoring satellite health flags.

A.17.21 Command Packet 0x3C

This packet requests the current satellite tracking status. The GPS receiver returns Packet

0x5C if data is available.

Table A-24. Command Packet 0x3C Data Format

Byte Item Type Value Meaning

0 Satellite # Byte 0

1 - 32

All satellites in the current tracking set Desired satellite

A-28 Lassen-SK8 Embedded GPS Module

A.17.22 Report Packet 0x41

This packet provides the current GPS time of week and the week number. The GPS receiver sends this packet in response to Packet 0x21 and during an update cycle. Update cycles occur approximately every 5 seconds. The data format is shown below.

Table A-25. Report Packet 0x41 Data Formats

Byte Item Type Units

0-3 GPS time of week SINGLE seconds 4-5 Extended GPS week number INTEGER weeks 6-9 GPS/UTC offset SINGLE seconds

Trimble Standard Interface Protocol

Note – UTC time lags behind GPS time by an integer number of seconds UTC = (GPS time) - (GPS UTC offset).

Caution – GPS week numbers run from 0 to 1023 and then cycles back to week #0. Week # 0 began January 6, 1980. There will be another week #0 beginning August 22, 1999. The extended GPS week number however, does not cycle back to 0. For example, August 22, 1999 starts week number 1024.

The seconds count begins with “0” each Sunday morning at midnight GPS time. A negative indicated time-of-week indicates that time is not yet known; in that case, the packet is sent only on request. The following table shows the relationship between the information in Packet 0x41, and the Packet 0x46 status code.

Table A-26. Packets 0x41 and 0x46 Status Code Relationships

Approximate Time Accuracy Time Source Sign (TOW)

none no time at all - 0x01 unknown approximate time

from real-time clock or Packet

2E 20-50 msec + clock drift time from satellite + not 0x01 full accuracy time from GPS

solution

+ 0x01

+ 0x00

Packet 46 Status Code

Lassen-SK8 Embedded GPS Module A-29

Note – Before using the GPS time from Packet 0x41, verify that the Packet 0x46 status code is 00 (“Doing position fixes”). This will ensure the most accurate GPS time.

Trimble Standard Interface Protocol

A.17.23 Report Packet 0x42

This packet provides current GPS position fix in XYZ ECEF coordinates. If the I/O “position” option is set to “XYZ ECEF” and the I/O “precision-of-position output” is set to single-precision, then the GPS receiver sends this packet each time a fix is computed. The data format is shown below.

Table A-27. Report Packet 0x42 Data Formats

Byte Item Type Units

0-3 X SINGLE meters 4-7 Y SINGLE meters 8-11 Z SINGLE meters 12-15 time-of-fix SINGLE seconds

The time-of-fix is in GPS time or UTC as selected by the I/O “timing” option. Packet 83 provides a double-precision version of this information.

A.17.24 Report Packet 0x43

This packet provides current GPS velocity fix in XYZ ECEF coordinates. If the I/O “velocity” option is set to “XYZ ECEF, then the GPS receiver sends this packet each time a fix is computed. The data format is shown below.

Table A-28. Report Packet 0x43 Data Formats

Byte Item Type Value

0-3 X velocity SINGLE meters/second 4-7 Y velocity SINGLE meters/second 8-11 Z velocity SINGLE meters/second 12-15 bias rate SINGLE meters/second 16-19 time-of-fix SINGLE seconds

The time-of-fix is in GPS time or UTC as selected by the I/O “timing” option.

A-30 Lassen-SK8 Embedded GPS Module

A.17.25 Report Packet 0x45

This packet provides information about the version of software in the Navigation and Signal Processors. The GPS receiver sends this packet after power-on and in response to Packet 0x1F.

Table A-29. Report Packet 0x45 Data Formats

Byte Item Type

0 Major version number BYTE 1 Minor version number BYTE 2 Month BYTE 3 Day BYTE 4 Year number minus 1900 BYTE 5 Major revision number BYTE 6 Minor revision number BYTE 7 Month BYTE 8 Day BYTE 9 Year number minus 1900 BYTE

Trimble Standard Interface Protocol

The first 5 bytes refer to the Navigation Processor and the second 5 bytes refer to the Signal Processor.

Lassen-SK8 Embedded GPS Module A-31

Trimble Standard Interface Protocol

A.17.26 Report Packet 0x46

This packet provides information about the satellite tracking status and the operational health of the Receiver. The receiver sends this packet after power-on or software-initiated resets, in response to Packet 0x26 and, during an update cycle. Packet 0x4B is always sent with this packet.

Table A-30. Report Packet 0x46 Data Formats

Byte Item Type Value Meaning

0 Status Code BYTE 0 h Doing position fixes

1 Status codes BYTE 0-7 b See Table A-31

01 h Don't have GPS time yet 02 h need initialization 03 h PDOP is too high 08 h No usable satellites 09 h Only 1 usable satellite 0A h Only 2 usable satellites 0B h Only 3 usable satellites 0C h The chosen satellite is unusable

The error codes in Byte 1 of Packet 0x46 are encoded into individual bits within the byte. The bit positions and their meanings are shown below.

Table A-31. Report Packet 0x46 Bit Positions and Descriptions

Status Code Bit Position Meaning if bit value = 1

0 (LSB) 1 2 3 4 5 6 7 (MSB)

Note – After this status is detected, its bit remains set until the receiver is reset.

A.17.27 Report Packet 0x47

No battery back-up at start-up (note 1) not used not used not used Antenna feed line fault (open or short) not used not used not used

This packet provides received signal levels for all satellites currently being tracked or on which tracking is being attempted (i.e., above the elevation mask and healthy according to

A-32 Lassen-SK8 Embedded GPS Module

Trimble Standard Interface Protocol

the almanac). The receiver sends this packet only in response to Packet 0x27. The data format is shown below.

Table A-32. Report Packet 0x47 Data Formats

Byte Item Type

0 Count BYTE 1 Satellite number 1 BYTE 2- 5 Signal level 1 SINGLE 6 Satellite number 2 BYTE 7-10 Signal level 2 SINGLE (etc.) (etc.) (etc.)

Up to 8 satellite number/signal level pairs may be sent, indicated by the count field. Signal level is normally positive. If it is zero then that satellite has not yet been acquired. If it is negative then that satellite is not currently in lock. The absolute value of signal level field is the last known signal level of that satellite. The signal level provided in this packet is a linear measure of the signal strength after correlation or de-spreading. Units, either AMU or dBHz, are controlled by Packet 0x35.

A.17.28 Report Packet 0x48

This packet provides the most recent 22-byte ASCII message broadcast in the GPS satellite navigation message. The receiver sends this packet in response to Packet 0x28.

The message effectively is a bulletin board from the Air Force to GPS users. The format is free-form ASCII and is often enabled or encrypted. The message may be blank.

A.17.29 Report Packet 0x4A

This packet provides current GPS position fix in LLA (latitude, longitude, and altitude) coordinates. If the I/O “position” option is set to “LLA” and the I/O “precision-of-position output” is set to single-precision, then the receiver sends this packet each time a fix is computed.

Lassen-SK8 Embedded GPS Module A-33

Trimble Standard Interface Protocol

A.17.30 Main 0x4A Report Packet Type

The data format is shown below:

Table A-33. Report Packet 0x4A Data Formats

Byte Item Type Units

0-3 Latitude SINGLE radians; + for north, - for south 4-7 Longitude SINGLE radians; + for east, - for west 8-11 Altitude SINGLE meters (HAE or MSL) 2-15 Clock Bias SINGLE meters 6-19 Time-of-Fix SINGLE seconds (GPS or UTZ)

The LLA conversion is done according to the datum selected using Packet 0x8E-15. The default is WGS-84. Altitude is referred to the datum ellipsoid or the MSL Geoid, depending on which I/O “LLA altitude” option is selected. The time-of-fix is in GPS time or UTC, depending on which I/O “timing” option is selected.

This packet also is sent at start-up with a negative time-of-fix to report the current known position. Packet 0x84 provides a double-precision version of this information

Caution – When converting from radians to degrees, significant and readily visible errors will be introduced by use of an insufficiently precise approximation for the constant PI. The value of the constant PI as specified in ICD-GPS-200 is 3.1415926535898.

A.17.31 Second 0x4A Packet Type

Report Packet 0x4A is also sent in response to the setting or requesting of the Reference Altitude Parameters using Command Packet 0x2A. These parameters can be used in the Manual 2-D mode.

Reference Altitude

The altitude used for manual 2-D positions if the altitude flag is set. Altitude is in units of HAE WGS-84 or MSL depending on the selected I/O options for the position.

A-34 Lassen-SK8 Embedded GPS Module

Altitude Flag

A flag that determines whether or not the Reference Altitude will be used. If set, it will be used. If cleared, altitude hold (last 3-D altitude) will be used. The data format is shown in the following table.

Table A-34. Reference Altitude

Byte Item Type Units

0-3 Reference Altitude SINGLE Meters 4-7 Reserved SINGLE 8 Altitude flag BYTE

A.17.32 Report Packet 0x4B

The receiver transmits this packet in response to packets 0x25 and 0x26 and following a change in state. In conjunction with Packet 0x46, “health of receiver,” this packet identifies the receiver and may present status messages. The machine ID can be used by equipment communicating with the receiver to determine the type of receiver to which the equipment is connected. Then the interpretation and use of packets can be adjusted accordingly.

Trimble Standard Interface Protocol

Table A-35. Report Packet 0x4B Data Formats

Byte Item Type/Value Status/Meaning

0 Machine ID BYTE 6-channel receiver 1 Status 1 BYTE see Table A-36 2 Status 2 BYTE Bit 0 = Super packets supported

The status codes are encoded into individual bits within the bytes. The bit positions and their meanings are shown in Table A-36.

Table A-36. Report Packet 0x4B Bit Positions and Descriptions

Status 1 Bit Position Meaning if bit value = 1

0 (LSB) not used 1 not used 2 not used 3 The almanac stored in the receiver, is not complete and

current

4-7 not used

Lassen-SK8 Embedded GPS Module A-35

Trimble Standard Interface Protocol

A.17.33 Report Packet 0x4D

This packet provides the current value of the receiver master oscillator offset in Hertz at carrier. This packet contains one SINGLE number. The receiver sends this packet in response to Packet 0x2D. The permissible offset varies with the receiver unit.

A.17.34 Report Packet 0x4E

Indicates whether the receiver accepted the time given in a Set GPS time packet. the receiver sends this packet in response to Packet 0x2E. This packet contains one byte.

Table A-37. Report Packet 0x4E Data Formats

Value Meaning

ASCII “Y” The receiver accepts the time entered via Packet 2E. The receiver has

not yet received the time from a satellite.

ASCII “N” The receiver does not accept the time entered via Packet 2E. The

receiver has received the time from a satellite and uses that time. The receiver disregards the time in Packet 0x 2E.

A-36 Lassen-SK8 Embedded GPS Module

Trimble SK8, Lassen-SK8 Reference Manual

Specifications and Main Features

Frequently Asked Questions

User Manual