Lassen™ SQ GPS
Receiver
System Designer Reference Manual
F
Part Number 47838-00
Revision A
June 2002
Corporate Office
Release Notice
Trimble Navigation Limited
Components Technologies Division
645 North Mary Avenue
Post Office Box 3642
Sunnyvale, CA 94088-3642
U.S.A.
Phone: +1-408-481-8940, 1-800-545-7762
Fax: +1-408-481-7744
www.trimble.com
Support Offices
Trimble Navigation Limited
Components Technologies Division
645 North Mary Avenue
Post Office Box 3642
Sunnyvale, CA 94088-3642
U.S.A.
Phone: +1-408-481-8940, 1-800-545-7762
Fax: +1-408-481-7744
Trimble Navigation Europe Limited
Trimble House
Meridian Office Park
Osborn Way, Hook
Hampshire RG27 9HX
England
Phone: +44-1256-760-150
Fax: +44-1-256-760-148
Copyright and Trademarks
© 2002 Trimble Navigation Limited. All rights
reserved. No part of this manual may be copied,
reproduced, translated, or reduced to any
electronic medium or machine-readable form for
any use other than with the Lassen™ SQ GPS
Receiver.
This is the June 2002 release (Revision A) of the
Lassen™ SQ GPS Receiver System Designer
Reference Manual, part number 47838-00.
The following limited warranties give you specific
legal rights. You may have others, which vary
from state/jurisdiction to state/jurisdiction.
Hardware Limited Warranty
Trimble warrants that this Trimble hardware
product (the “Product”) shall be free from defects
in materials and workmanship and will
substantially conform to Trimble’s applicable
published specifications for the Product for a
period of one (1) year, starting from the date of
delivery. The warranty set forth in this paragraph
shall not apply to software/firmware products.
Software and Firmware License, Limited
Warranty
This Trimble software and/or firmware product
(the “Software”) is licensed and not sold. Its use is
governed by the provisions of the applicable End
User License Agreement (“EULA”), if any,
included with the Software. In the absence of a
separate EULA included with the Software
providing different limited warranty terms,
exclusions, and limitations, the following terms
and conditions shall apply. Trimble warrants that
this Trimble Software product will substantially
conform to Trimble’s applicable published
specifications for the Software for a period of
ninety (90) days, starting from the date of
delivery.
Warranty Remedies
The Globe & Triangle logo, Trimble, Colossus,
FirstGPS, and Lassen, are trademarks of Trimble
Navigation Limited.
The Sextant logo with Trimble is a trademark of
Trimble Navigation Limited, registered in the
United States Patent and Trademark Office.
All other trademarks are the property of their
respective owners.
Trimble's sole liability and your exclusive remedy
under the warranties set forth above shall be, at
Trimble’s option, to repair or replace any Product
or Software that fails to conform to such warranty
(“Nonconforming Product”), or refund the
purchase price paid by you for any such
Nonconforming Product, upon your return of any
Nonconforming Product to Trimble in accordance
with Trimble’s standard return material
authorization procedures.
Warranty Exclusions and Disclaimer
These warranties shall be applied only in the event
and to the extent that: (i) the Products and
Software are properly and correctly installed,
configured, interfaced, maintained, stored, and
operated in accordance with Trimble’s relevant
operator's manual and specifications, and; (ii) the
Products and Software are not modified or
misused. The preceding warranties shall not apply
to, and Trimble shall not be responsible for defects
or performance problems resulting from (i) the
combination or utilization of the Product or
Software with products, information, data,
systems or devices not made, supplied or specified
by Trimble; (ii) the operation of the Product or
Software under any specification other than, or in
addition to, Trimble's standard specifications for
its products; (iii) the unauthorized modification or
use of the Product or Software; (iv) damage
caused by accident, lightning or other electrical
discharge, fresh or salt water immersion or spray;
or (v) normal wear and tear on consumable parts
(e.g., batteries).
THE WARRANTIES ABOVE STATE TRIMBLE'S
ENTIRE LIABILITY, AND YOUR EXCLUSIVE
REMEDIES, RELATING TO PERFORMANCE OF
THE PRODUCTS AND SOFTWARE. EXCEPT AS
OTHERWISE EXPRESSLY PROVIDED HEREIN
THE PRODUCTS, SOFTWARE, AND
ACCOMPANYING DOCUMENTATION AND
MATERIALS ARE PROVIDED “AS-IS” AND
WITHOUT EXPRESS OR IMPLIED WARRANTY
OF ANY KIND BY EITHER TRIMBLE
NAVIGATION LIMITED OR ANYONE WHO HAS
BEEN INVOLVED IN ITS CREATION
PRODUCTION, INSTALLATION, OR
DISTRIBUTION, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE, TITLE, AND
NONINFRINGEMENT. THE STATED EXPRESS
WARRANTIES ARE IN LIEU OF ALL
OBLIGATIONS OR LIABILITIES ON THE PART
OF TRIMBLE ARISING OUT OF, OR IN
CONNECTION WITH, ANY PRODUCTS OR
SOFTWARE. SOME STATES AND
JURISDICTIONS DO NOT ALLOW LIMITATIONS
ON DURATION OR THE EXCLUSION OF AN
IMPLIED WARRANTY, SO THE ABOVE
LIMITATION MAY NOT APPLY TO YOU
,
,
.
TRIMBLE NAVIGATION LIMITED IS NOT
RESPONSIBLE FOR THE OPERATION OR
FAILURE OF OPERATION OF GPS SATELLITES
OR THE AVAILABILITY OF GPS SATELLITE
SIGNALS
.
Limitation of Liability
TRIMBLE’S ENTIRE LIABILITY UNDER ANY
PROVISION HEREIN SHALL BE LIMITED TO
THE GREATER OF THE AMOUNT PAID BY YOU
FOR THE PRODUCT OR SOFTWARE LICENSE OR
.$25.00. TO
U.S
PERMITTED BY APPLICABLE LAW, IN NO
EVENT SHALL TRIMBLE OR ITS SUPPLIERS BE
LIABLE FOR ANY INDIRECT, SPECIAL
INCIDENTAL, OR CONSEQUENTIAL DAMAGES
WHATSOEVER UNDER ANY CIRCUMSTANCE
OR LEGAL THEORY RELATING IN ANY WAY TO
THE PRODUCTS, SOFTWARE, AND
ACCOMPANYING DOCUMENTATION AND
MATERIALS
LIMITATION, DAMAGES FOR LOSS OF
BUSINESS PROFITS, BUSINESS INTERRUPTION
LOSS OF BUSINESS INFORMATION, OR ANY
OTHER PECUNIARY LOSS
WHETHER TRIMBLE HAS BEEN ADVISED OF
THE POSSIBILITY OF ANY SUCH LOSS AND
REGARDLESS OF THE COURSE OF DEALING
WHICH DEVELOPS OR HAS DEVELOPED
BETWEEN YOU AND TRIMBLE. BECAUSE SOME
STATES AND JURISDICTIONS DO NOT ALLOW
THE EXCLUSION OR LIMITATION OF LIABILITY
FOR CONSEQUENTIAL OR INCIDENTAL
DAMAGES, THE ABOVE LIMITATION MAY NOT
APPLY TO YOU
THE MAXIMUM EXTENT
, (
INCLUDING, WITHOUT
),
REGARDLESS OF
.
,
,
Contents
1Starter Kit
Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Starter Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Removing the Lassen SQ GPS Module . . . . . . . . . . . . . . 4
Receiver Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Interface Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
TSIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
NMEA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Ordering Starter Kit Components. . . . . . . . . . . . . . . . . . . . . 7
Starter Kit Interface Unit . . . . . . . . . . . . . . . . . . . . . . . . . 8
Serial Port Interface . . . . . . . . . . . . . . . . . . . . . . . 11
Pulse-Per-Second (PPS) . . . . . . . . . . . . . . . . . . . . . 12
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Software Toolkit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2 Hardware Integration
General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Digital IO/Power Connector . . . . . . . . . . . . . . . . . . . 21
RF Connector. . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Digital IO/Power Connector Pinout . . . . . . . . . . . . . . . 24
Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Lassen SQ GPS Receiver v
Contents
Pulse-Per-Second (PPS). . . . . . . . . . . . . . . . . . . . . . . . . 28
Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
GPS Antennas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3 Software Interface
Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Communicating with the Lassen SQ GPS receiver Module . . . . . . 35
Software Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Port Configuration . . . . . . . . . . . . . . . . . . . . . . . . 35
Port Protocol and Data Output Options . . . . . . . . . . . . . . . . . 37
Protocol Configuration and Interface . . . . . . . . . . . . . . 37
TSIP Data Output Modes . . . . . . . . . . . . . . . . . . . . 38
Automatic TSIP Output Options and Defaults. . . . . . . . . . 38
Automatic TSIP Output Packets (fixed rate) . . . . . . . . . . . 39
Packet Output Order . . . . . . . . . . . . . . . . . . . . . . . 40
NMEA 0183 Protocol and Data Output Options. . . . . . . . . 41
Custom Port Configuration . . . . . . . . . . . . . . . . . . . . . . . 42
Timing Applications . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Extended GPS Week Number . . . . . . . . . . . . . . . . . . 46
4 Operation and Performance
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
GPS Satellite Message . . . . . . . . . . . . . . . . . . . . . . . . . 49
Satellite Acquisition and Time to First Fix . . . . . . . . . . . . . . . 50
Cold-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Warm Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Hot Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Garage Search Strategy . . . . . . . . . . . . . . . . . . . . . 52
System Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Satellite Mask Settings . . . . . . . . . . . . . . . . . . . . . . . . . 54
Elevation Mask . . . . . . . . . . . . . . . . . . . . . . . . . . 55
SNR Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
DOP Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
vi Lassen SQ GPS Receiver
Contents
PDOP Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Standard Operating Modes . . . . . . . . . . . . . . . . . . . . . . . 57
Fix Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Position Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Coordinate Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
TSIP Coordinate Systems . . . . . . . . . . . . . . . . . . . . 59
NMEA 0183 . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Performance Characteristics . . . . . . . . . . . . . . . . . . . . . . 61
Update Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Dynamic Limits . . . . . . . . . . . . . . . . . . . . . . . . . 61
Re-Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . 62
GPS Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Serial Time Output . . . . . . . . . . . . . . . . . . . . . . . . 64
Pulse-Per-Second (PPS) . . . . . . . . . . . . . . . . . . . . . 64
System Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . 65
A Trimble Standard Interface Protocol (TSIP)
Interface Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Packet Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Automatic Output Packets . . . . . . . . . . . . . . . . . . . . . . . 70
Customizing Receiver Operations . . . . . . . . . . . . . . . . . . . 71
Automatic Position and Velocity Reports. . . . . . . . . . . . . . . . 71
Initialization Packets to Speed Start-up. . . . . . . . . . . . . . . . . 72
Packets Output at Power-Up . . . . . . . . . . . . . . . . . . . . . . 73
Timing Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Satellite Data Packets . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Backwards Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 74
Recommended TSIP Packets . . . . . . . . . . . . . . . . . . . . . . 75
Command Packets Sent to the Receiver . . . . . . . . . . . . . . . . 76
Report Packets Sent by the Receiver to the User . . . . . . . . . . . . 78
Key Setup Parameters or Packet BB . . . . . . . . . . . . . . . . . . 79
Set Fix Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Dynamics Code . . . . . . . . . . . . . . . . . . . . . . . . . 81
Lassen SQ GPS Receiver vii
Contents
Packet Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Elevation Mask . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Signal Level Mask . . . . . . . . . . . . . . . . . . . . . . . . 82
DOP Mask and Switch . . . . . . . . . . . . . . . . . . . . . . 83
Command Packet 0x1E - Clear Battery Backup, then Reset. . . 84
Command Packet 0x1F - Request Software Versions . . . . . . 85
Command Packet 0x21 - Request Current Time . . . . . . . . . 85
Command Packet 0x23 - Initial Position
(XYZ Cartesian ECEF) . . . . . . . . . . . . . . . . . . 85
Command Packet 0x24 - Request GPS Position Fix Mode . . . 86
Command Packet 0x25 - Initiate Soft Reset & Self Test . . . . 86
Command Packet 0x26 - Request Health . . . . . . . . . . . . 86
Command Packet 0x27 - Request Signal Levels. . . . . . . . . 86
Command Packet 0x2A - Altitude for 2-D Mode . . . . . . . . 86
Command Packet 0x2B - Initial Position . . . . . . . . . . . . 88
Command Packet 0x2D - Request Oscillator Offset. . . . . . . 88
Command Packet 0x2E - Set GPS Time . . . . . . . . . . . . . 89
Command Packet 0x31 - Accurate Initial Position . . . . . . . 90
Command Packet 0x32 - Accurate Initial Position, . . . . . . . 91
Command Packet 0x35 - Set/Request I/O Options . . . . . . . 92
Command Packet 0x37 - Request Last Position and Velocity . . 95
Command Packet 0x38 - Request/Load Satellite System Data . 95
Command Packet 0x3C - Request Current Satellite Tracking . 97
Report Packet 0x41 - GPS Time . . . . . . . . . . . . . . . . . 97
Report Packet 0x42 - Single-Precision Position Fix . . . . . . . 99
Report Packet 0x43 - Velocity Fix, XYZ ECEF . . . . . . . . . 100
Report Packet 0x45 - Software Version Information. . . . . . . 101
Report Packet 0x46 - Health of Receiver . . . . . . . . . . . . 102
Report Packet 0x47 - Signal Levels for all Satellites . . . . . . 103
Report Packet 0x4A - 20 Byte Format . . . . . . . . . . . . . . 104
Report Packet 0x4A - 9 Byte Format . . . . . . . . . . . . . . 105
Report Packet 0x4B - Machine/Code ID and Additional Status . 106
viii Lassen SQ GPS Receiver
Contents
Report Packet 0x4D - Oscillator Offset . . . . . . . . . . . . . 107
Report Packet 0x4E - Response to Set GPS Time . . . . . . . . 107
Report Packet 0x55 - I/O Options . . . . . . . . . . . . . . . . 108
Report Packet 0x56 - Velocity Fix, East-North-Up (ENU) . . . 110
Report Packet 0x57 - Information About Last Computed Fix . . 111
Report Packet 0x58 - Satellite System Data/Acknowledge . . . 112
Report Packet 0x5C - Satellite Tracking Status . . . . . . . . . 116
Report Packet 0x6D - All-In-View Satellite Selection . . . . . . 118
Command Packet 0x70 - Filter Control . . . . . . . . . . . . . 119
Report Packet 0x70. . . . . . . . . . . . . . . . . . . . . . . . 120
Command Packet 0x7A . . . . . . . . . . . . . . . . . . . . . 121
Report Packet 0x7B . . . . . . . . . . . . . . . . . . . . . . .122
Report Packet 0x82 - Differential Position Fix Mode . . . . . . 122
Report Packet 0x83 - Double-Precision XYZ Fix and Bias . . 123
Report Packet 0x84 - Double-Precision LLA Fix and Bias . . 124
Packets 0x8E and 0x8F - Superpacket . . . . . . . . . . . . . . 124
Command Packet 0xBB - Navigation Configuration . . . . . . 125
Command Packet 0xBC - Protocol Configuration . . . . . . . . 126
TSIP Superpackets . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Command Packet 0x8E-20 - Request Last Fix with Extra Info. . 128
Report Packet 0x8F-20 - Last Fix with Extra Info. (binary) . . . 129
Command Packet 0x8E-26 - Non-Volatile Memory Storage . . 132
Report Packet 0x8F-26 - Non-Volatile Memory Status . . . . . 132
B TSIP Tool kit User’s Guide
SQ_Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Delta Position . . . . . . . . . . . . . . . . . . . . . . . . . .135
File Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
C NMEA 0183
The NMEA 0183 Communication Interface . . . . . . . . . . . . . . 138
NMEA 0183 Message Format . . . . . . . . . . . . . . . . . . . . . 139
Field Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Lassen SQ GPS Receiver ix
Contents
NMEA 0183 Message Options . . . . . . . . . . . . . . . . . . . . . 142
NMEA 0183 Message Formats . . . . . . . . . . . . . . . . . . . . . 143
GGA - GPS Fix Data. . . . . . . . . . . . . . . . . . . . . . . 143
GLL - Geographic Position - Latitude/Longitude . . . . . . . . 144
GSA - GPS DOP and Active Satellites . . . . . . . . . . . . . 145
GSV - GPS Satellites in View . . . . . . . . . . . . . . . . . . 146
RMC - Recommended Minimum Specific GPS/Transit Data . . 147
VTG - Track Made Good and Ground Speed . . . . . . . . . . 148
ZDA - Time & Date . . . . . . . . . . . . . . . . . . . . . . . 149
Exception Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Power-up with No BBRAM . . . . . . . . . . . . . . . . . . . 150
Power-up with BBRAM . . . . . . . . . . . . . . . . . . . . . 150
Interruption of GPS Signal . . . . . . . . . . . . . . . . . . . . 151
D Specifications and Mechanical Drawings
Lassen SQ GPS Receiver Specifications . . . . . . . . . . . . . . . . 154
Performance . . . . . . . . . . . . . . . . . . . . . . . . . . .154
Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Physical. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Ultra Compact Embedded Antenna . . . . . . . . . . . . . . . . . . . 159
Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
LNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Overall Specifications . . . . . . . . . . . . . . . . . . . . . . 160
Storage Conditions . . . . . . . . . . . . . . . . . . . . . . . . 160
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Compact Magnetic Mount Antenna. . . . . . . . . . . . . . . . . . . 162
Antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
LNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Overall Specifications . . . . . . . . . . . . . . . . . . . . . . 163
Storage Conditions . . . . . . . . . . . . . . . . . . . . . . . . 163
x Lassen SQ GPS Receiver
Contents
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Compact Unpackaged Antenna . . . . . . . . . . . . . . . . . . . . . 166
Glossary
Lassen SQ GPS Receiver xi
Contents
xii Lassen SQ GPS Receiver
About this Manual
Welcome to System Designer Reference Manual for the Lassen SQ
GPS receiver. This manual describes how to integrate and operate the
Lassen SQ GPS receiver.
If you are not familiar with GPS, visit Trimble’s website,
www.trimble.com, for an interactive look at Trimble and GPS.
Trimble assumes that you are familiar with Microsoft Windows and
know how to use a mouse, select options from menus and dialogs,
make selections from lists, and refer to online help.
Technical Assistance
If you have a problem and cannot find the information you need in the
product documentation, contact the Trimble Technical Assistance
Center at 800-767-4822.
Your Comments
Your feedback about the supporting documentation helps us to
improve it with each revision. To forward your comments, send an email to ReaderFeedback@trimble.com.
Lassen SQ GPS Receiver xiii
About this Manual
xiv Lassen SQ GPS Receiver
CHAPTER
1
Starter Kit
■
Product Overview
■
Starter Kit
■
Receiver Performance
■
Interface Protocols
■
Ordering Starter Kit Components
■
Starter Kit Interface Unit
■
Power
■
Hardware Setup
■
Software Toolkit
1
1 Starter Kit
1.1
Product Overview
The Lassen SQ GPS receiver is a full featured, ultra low power
receiver on a miniature form factor, suitable for a variety of mobile,
embedded applications. The Lassen SQ GPS receiver incorporates
Trimble’s FirstGPS
Colossus RF down converter and IO-TS-C33 baseband chip. The IOTS-C33 integrates Trimble’s IO digital signal processor with the
Epson C33 RISC processor, real-time clock, UART, and 1Mbit
memory. Together with the colossus RF, this implementation of
FirstGPS technology makes possible one of the smallest
(26 mm x 26 mm x 6mm) and lowest power (100mW) GPS modules
available.
The Lassen SQ GPS receiver outputs a complete position, velocity,
and time (PVT) solution in the NMEA Version 3.0 ASCII protocol,
and the Trimble TSIP binary protocol. A Pulse-Per-Second signal is
available for very accurate timing applications.
TM
architecture in the form of two ASICS:
2 Lassen SQ GPS Receiver
1.2
Starter Kit
Starter Kit 1
The Starter Kit makes it simple to evaluate the Lassen SQ GPS
receiver’s exceptional performance. The Starter Kit can be used as a
platform for configuring the receiver module and as a platform for
troubleshooting your design. The Starter Kit includes:
• Shielded Lassen SQ GPS module mounted on an interface
motherboard in a durable metal enclosure. The motherboard
accepts 9 - 32 VDC power and provides regulated +3.3V power
to the Lassen SQ GPS receiver. The motherboard also contains:
– 3.6V lithium battery that provides back-up power to the
receiver.
– Circuitry to convert the TTL output to RS-232, enabling
the user to connect the RS-232 port in the Starter Kit to the
PC COM port via an RS-232 cable connection.
• Compact Magnetic-Mount GPS Antenna with a 5 meter cable.
• Ultra-Compact Embedded Antenna with an 8 cm cable.
• 9-pin RS-232 interface cable.
• AC/DC power supply adapter (input: 100-240VAC,
output: 12 VDC).
• DC power cable.
• Cigarette lighter adapter power cable.
• CD containing software tools used to communicate with the
receiver, the System Designer Reference Manual, and “C”
programming source routines to be used as a template for
communicating with the receiver.
Lassen SQ GPS Receiver 3
1 Starter Kit
1.2.1
Removing the Lassen SQ GPS Module
The Lassen SQ GPS module is secured to the motherboard with
double-sided adhesive tape allowing for easy removal and integration
with the user’s application. (The adhesive tape used by Trimble is 3M
Scotch, part number 4945).
Follow these steps to remove the module from the motherboard:
• Unplug the I/O cable and the RF cable from the module.
• Use a small flat-head screw driver to pry the Lassen SQ GPS
receiver module off the motherboard.
Warning – Once the Lassen SQ GPS receiver module is removed from
the motherboard, the double-sided tape looses some of it’s adhesive
quality. This adhesive tape may only be re-used for laboratory testing. The
original adhesive tape should not be re-used for drive testing the Starter
Kit interface unit because the module could loosen and cause short circuit
when contacting other motherboard components. If drive testing is
required, use a new piece of double-sided adhesive tape to re-attach the
Lassen SQ GPS receiver module to the motherboard.
4 Lassen SQ GPS Receiver
1.3
Receiver Performance
The Lassen SQ GPS receiver 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
where small size and extremely low power consumption are required.
The receiver features Trimble's latest signal processing code, a highgain RF section for compatibility with standard 27 dB active gain GPS
antennas, and a CMOS TTL level pulse-per-second (PPS) output for
timing applications or for use as a general purpose synchronization
signal.
The Lassen SQ GPS receiver acquires a position fix with minimal
delay after power cycling. The battery back-up RAM is used to keep
the Real Time clock (RTC) alive, and to store the following:
• Almanac
Starter Kit 1
• Ephemeris
• Last position
User settings such as port parameters and NMEA settings can be
stored in the receiver’s non-volatile (Flash) memory. These settings
are retained without application of main power or battery back-up
power.
The Lassen SQ GPS receiver has a single configurable serial I/O
communication port.
Warning – When customizing port assignments or characteristics,
confirm that your changes do not affect your ability to communicate with
the receiver (see Chapter 3, Software Interface).
Lassen SQ GPS Receiver 5
1 Starter Kit
1.4
Interface Protocols
The Lassen SQ GPS receiver operates using one of two protocols —
Trimble Standard Interface Protocol (TSIP) or NMEA 0183. The
factory default setting for the I/O port is TSIP bi-directional. Protocol
selection and port characteristics are user configurable.
1.4.1
1.4.2
TSIP
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 20 commands and their associated response packets for use in
configuring the Lassen SQ GPS receiver to meet user requirements.
NMEA
NMEA 0183 is an industry standard protocol common to marine
applications. NMEA provides direct compatibility with other NMEAcapable devices such as chart plotters, radars, etc. The Lassen SQ GPS
receiver supports most NMEA messages for GPS navigation. NMEA
messages and output rates can be user selected as required.
6 Lassen SQ GPS Receiver
1.5
Ordering Starter Kit Components
The Lassen SQ GPS receiver is available in a Starter Kit or as an
individual module and associated antenna. The Starter Kit
(PN 47225-00) includes all the components necessary to quickly test
and integrate the module:
• Compact Magnetic-Mount Antenna with 5m cable
• Ultra-Compact Embedded Antenna with 8cm cable
• AC/DC power supply adapter
• DC Power cable (3-wire)
• RS-232 interface cable DB9M/DB9F (pin to pin)
• Cigarette lighter adapter power cable
• CD-ROM containing software tools and the System Designer
Reference Manual
Starter Kit 1
Table 1.1 provides ordering information for the Lassen SQ GPS
module and the associated antennas and cables.
Table 1.1 Lassen SQ GPS Receiver Ordering Information
Products Part Number
Lassen SQ GPS receiver Module 46240-00
Lassen SQ GPS receiver Starter Kit 47225-00
Lassen SQ GPS receiver antenna transition cable 47274
Ultra-Compact Embedded Antenna, 3.3V, 8cm cable 45336-00
Compact Unpackaged Antenna, 3V, 11cm cable 39265-51
Compact Magnetic Mount Antenna, 3V, 5m cable 39265-50
Note – Part numbers are subject to change. Confirm part numbers
with your Trimble representative when placing your order.
Lassen SQ GPS Receiver 7
1 Starter Kit
1.6
Starter Kit Interface Unit
The Starter Kit interface unit consists of a Lassen SQ GPS module
attached to an interface motherboard, housed in a sturdy metal
enclosure. This packaging simplifies testing and evaluation of the
module by providing an RS-232 serial interface which is compatible
with most PC communication ports. Power (9-32 VDC) is supplied
through the power connector on the front of the interface unit. The
motherboard features a switching power supply which converts this
voltage input to the 3.3 volts required by the module. The DB9
connector allows for an easy connection to a PC serial port using the
serial interface cable provided in the Starter Kit. The metal enclosure
protects the module and the motherboard for testing outside of the
laboratory environment.
The Lassen SQ GPS receiver is a single module encased in a sturdy
metal enclosure. The dimensions of the receiver in this enclosure are
26 mm H x 26 mm L x 6 mm H (1.02” W x 1.02” L x 0.24” H). A
straight-in, panel-mount RF connector (J1) supports the GPS antenna
connection. The center conductor of the coaxial connector also
supplies +3.3 VDC for the Low Noise Amplifier of the active antenna.
An 8-pin (2x4), 0.09 inch header (J2) supports the serial interface
(CMOS TTL level), the pulse-per-second (PPS) signal (CMOS TTL
level), and the input power (+3.3 VDC). Figur e1.1 illustrates the
module in the metal enclosure.
8 Lassen SQ GPS Receiver
Starter Kit 1
Bottom Shield
Figure 1.1 Lassen SQ GPS receiver Module
The interface motherboard includes a 9 to 32 VDC switching power
supply which provides regulated +3.3 VDC power to the receiver, and
contains circuitry which provides an RS-232 interface to a computer.
A 3.6V lithium backup battery enables quick hot starts. The TTL level
PPS is brought directly out to Pin 9 of the Port 2 DB9 connector on the
front of the interface unit.
The Starter Kit includes an AC/DC converter for powering the module
from an AC wall socket. The metal enclosure (see Figure 1.2.)
provides 2 DB9 interface port connectors, an antenna connector, and a
power connector. Port 1 is for serial I/O.
Top Shield
Lassen SQ GPS Receiver 9
1 Starter Kit
The mounting plate is secured to the metal enclosure with four screws.
The eight pin I/O header on the receiver module connects to a mating
connector on a ribbon cable. The ribbon cable is attached to a mating
I/O connector on the interface motherboard. Figure 1.2 illustrates the
Starter Kit interface unit.
Figure 1.2 Starter Kit Interface Unit
Port 2
Port 1
10 Lassen SQ GPS Receiver
Starter Kit 1
1.6.1
Serial Port Interface
The Starter Kit interface unit is a DCE (Data Communication
Equipment) device. To connect to a host computer, or DTE (Data
Terminal Equipment) device, use a straight through cable. To connect
a Differential Radio (DCE device) to the receiver (DCE Device) use a
cross over cable or null modem cable.
Table 1.2 Port 1 Pinouts
Pin Description
1NC
2TX
3RX
4NC
5GND
6NC
7NC
8NC
9NC
Table 1.3 Port 2 Pinouts
Pin Description
1NC
2NC
3NC
4NC
5GND
6NC
7NC
8NC
9 PPS Out
Lassen SQ GPS Receiver 11
1 Starter Kit
1.6.2
Pulse-Per-Second (PPS)
The Lassen SQ GPS receiver provides a four microsecond wide,
CMOS compatible TTL level Pulse-Per-Second (PPS). The PPS is a
positive pulse available on pin 9 of the port 2 DB9 connector of the
interface unit (see Table 1.3). The rising edge of the PPS pulse is
synchronized with respect to UTC. The timing accuracy is ±95
nanoseconds when valid position fixes are being reported.
The rising edge of the pulse is typically less than 20 nanoseconds. The
distributed impedance of the attached signal line and input circuit can
affect the pulse shape and rise time. The PPS can drive a load up to
5mA without damaging the module. The falling edge of the pulse
should not be used. The PPS is always on (early PPS) and is driven by
the Real Time Clock (RTC) until the receiver acquires GPS time from
the satellite and generates position fixes. The PPS is output
immediately after main power is applied, and continues even if the
receiver loses GPS lock. The drift of the PPS, when the receiver is not
tracking satellites, is unspecified and should not be used for
synchronization.
Note – Trimble has measured better than 50 nanosecond accuracy on
the Lassen SQ GPS receiver’s PPS signal in static mode. For more
information on use of the Lassen SQ GPS receiver in timing
applications, contact your Trimble sales representative.
12 Lassen SQ GPS Receiver
1.7
Power
Starter Kit 1
The Lassen SQ GPS receiver receiver is designed for embedded
applications and requires a regulated +3.3 VDC input (+3.0 to +3.6
VDC). The receiver provided in the Starter Kit is installed on a
motherboard, providing a DC power regulator which converts a 9 to
32 VDC input to the regulated 3.3 VDC required by the receiver.
Power can be applied to the interface unit using one of three options:
the DC power cable (Figure 1.3), the AC/DC power converter
(Figure 1.4), or the cigarette lighter adapter.
Figure 1.3 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 un-terminated 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
and the antenna. The combined power consumption of the interface
unit with the receiver and the antenna is 133 - 145 milli-amps.
Note – To ensure compliance with CE conducted emissions
requirements when using the DC power cable, the Starter Kit interface
unit must be bonded to a ground plane.
Note – The yellow wire of the DC power cable is not used. Battery
back-up power is provided by a factory installed 3.6V lithium battery
on the motherboard.
Lassen SQ GPS Receiver 13
1 Starter Kit
The AC/DC power converter may be used as an alternate power source
for the interface unit. The AC/DC power converter converts 110 or 220
VAC to a regulated 12 VDC compatible with the interface unit. 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 country-specific. The input connector is a standard 3-prong
connector used on many desktop PCs.
Figure 1.4 AC/DC Power Converter
14 Lassen SQ GPS Receiver
1.8
Hardware Setup
The Lassen SQ GPS receiver supports the TSIP and NMEA protocols.
A single port supports both the input/output of TSIP messages and the
output of NMEA messages. Follow the steps below to setup the Starter
Kit
interface unit. Figure 1.5 illustrates the setup.
Starter Kit 1
Po we r
Supply
Lassen SQ GPS
Starter Kit
GPS
DC E
9 to 32 VDC
Re c e ive r
DC E
GPS
Antenna
Figure 1.5 Starter Kit Interface Unit
DTE
Computer
Lassen SQ GPS Receiver 15
1 Starter Kit
1. When using the TSIP protocol, connect one end of the 9-pin
serial interface cable to Port 1 of the interface unit. Connect the
other end of the cable to COM1 or COM2 on a PC. A 9-pin-to25-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 MCX
connector on the module. Place the antenna so that it has a clear
view of the sky.
Note – To remove the antenna cable, grasp the antenna mating MCX
connector and pull from the MCX connector mounted on the interface
unit.
3. Using either the DC power cable or an 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.
– 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.
16 Lassen SQ GPS Receiver
1.9
Software Toolkit
The CD provided in the Starter Kit contains the SQ_Monitor and the
TSIPCHAT interface programs used to monitor GPS performance and
to assist system integrators in developing a software interface for the
GPS module. These applications are described in detail in Appendix
B, TSIP User's Guide.
SQ_Monitor runs on the Windows 95/98/2000 platforms. TSIPCHAT
runs under the DOS operating system on a 386 or higher processor.
Following are quick start instructions for using the SQ_Monitor
application to monitor the receiver’s performance.
1. Connect one end of the serial interface cable to Port 1 of the
2. Turn on the DC power source or plug in the AC/DC converter.
Starter Kit 1
interface unit. Connect the other end of the cable to the COM
port of your PC.
3. Insert the CD in the computer’s CD-ROM drive.
4. The SQ_Monitor program may be run directly off the CD or it
may be copied onto your computer’s hard drive. To run the
program off the CD, initiate the SQ_Monitor.exe file.
5. When the SQ_Monitor screen appears, the TX and RX
indicators appear in the lower left corner of the status bar. A
blinking TX indicates that the PC is transmitting commands to
the receiver; a blinking RX indicates that the PC is receiving
reports from the receiver. If either of these indicators stop
blinking, there is no activity. The PC COM port settings appear
in the lower right corner of this same status bar.
6. After a GPS antenna is connected to the receiver and the
receiver has achieved a position fix, the transmitted position
reports, time, velocity, satellites tracked, and GPS receiver
status appear on the screen. The receiver also sends a health
report every few seconds, even if satellites are not being
tracked.
Lassen SQ GPS Receiver 17
1 Starter Kit
Note – If the SQ_Monitor program displays a question mark (?) in a
data field, the receiver has not reported a status for this field. If a (?)
remains in the data field, the GPS module may not be communicating
with the computer. Re-check the interface cable connections and verify
the serial port selection and settings. If the communication failure
continues after checking all connections and settings, please call the
Trimble Technical Assistance Center (TAC) at 1 (800) 767-4822.
18 Lassen SQ GPS Receiver
CHAPTER
2
Hardware Integration
In this chapter:
■
General Description
■
Connectors
■
Power Requirements
■
Serial Interface
■
Pulse-Per-Second (PPS)
■
Mounting
■
GPS Antennas
2
2 Hardware Integration
2.1
General Description
Trimble’s new Lassen SQ GPS receiver adds complete GPS
functionality to mobile products, in a postage-stamp-sized footprint
with ultra-low power consumption. Using Trimble’s breakthrough
FirstGPS™ architecture, the module delivers complete position,
velocity and time (PVT) solutions for use in mobile, battery-powered
applications such as cell phones, pagers, PDAs, and digital cameras.
The Lassen SQ GPS module is packaged in a tiny form factor
(26 mm x 26 mm x 6 mm, including the metal shield). It typically
requires only 100 mW of power (at 3.3 VDC). Total typical power
usage, including the Trimble 3.3 VDC miniature antenna, is 133 mW.
The module includes flash memory for field upgrades and for storing
the user configuration.
Figure 2.1 Lassen SQ GPS Receiver Board without Shield
20 Lassen SQ GPS Receiver
2.2
Connectors
Hardware Integration 2
2.2.1
Digital IO/Power Connector
The Lassen SQ GPS module uses a single 8-pin (2x4) male header
connector for both power and data I/O. The power and I/O connector,
J2, is a surface mount micro terminal strip. This connector uses 0.09
inch (2.286mm) high pins on 0.05 inch (1.27mm) spacing. The
manufacturer of this connector is Samtec, part number
ASP 69533-01.
Note – See Appendix D for mechanical drawings and specifications.
Mating Connectors
The customer must supply his own mating connector to the Lassen SQ
GPS receiver 8-pin (2x4) connector. There are two mating connectors
available:
• Surface-Mount Mating Connector
A recommended surface mount mating connector is Samtec’s
part number CLP-104-02.
When a surface-mount mating connector is chosen, the RF
connector must be attached to the Lassen SQ GPS module prior
to securing the module to the user’s PCB. The mounting tabs
may be used for securing the Lassen SQ GPS module to the
PCB when using the surface-mount mating scheme.
Lassen SQ GPS Receiver 21
2 Hardware Integration
• Cable Strip Mating Connector
A low profile, cable strip mating connector is the second I/O
mating method. A recommended cable strip part is Samtec’s
part number FFSD-04-?-XX part. The user will need to
substitute the following letters and numbers into the part
number when ordering this part where the '?' and 'XX' symbols
occur: for the '?' symbol substitute the letter S for single end or
D for double end; for the 'XX' symbol substitute the overall
length in inches, ± 1/8 inch, with a 2 inch minimum. Since the
signals are CMOS TTL level signals, Trimble does not
recommend cable lengths of longer than six inches.
If the cable strip I/O connector scheme is used, the connector
side of the Lassen SQ module will be facing up and the
mounting tabs will be on the top of the module away from PCB.
The RF connector is easily accessible, using this interfacing
methodology.
Figure 2.2 Cable Strip Mating Connector
22 Lassen SQ GPS Receiver
Hardware Integration 2
2.2.2
RF Connector
The RF connector mounted on the Lassen SQ module is a Hirose
connector, part number H.FL-R-SMT (10) 50 Ohm. The mating RF
connector is Hirose H.FL-LP-XXX where XXX depends on the cable
type.
Figure 2.3 Lassen SQ GPS Module with Connectors
Possible cable manufactures include the following:
• 1.48 mm diameter (single shield) cable:
– CO-6F/FH-SB manufactured by Hitachi Cable Ltd.
– UL1979 manufactured by Junkosha Co., Ltd.
– 0.8DS-PBE manufactured by Sumitomo Electric Industry
Co., Ltd.
• 1.32 mm diameter cable (double shield):
– A12B0733 manufactured by Junkosha Co., Ltd.
• 1.47 mm diameter cable (single shield):
– CXN2571 manufactured by W.L. Gore & Associated, Inc.
Lassen SQ GPS Receiver 23
2 Hardware Integration
Trimble offers three antennas for use with the Lassen SQ GPS receiver
receiver: The Ultra-Compact Embedded Antenna, which mates
directly to the RF connector. The Compact Unpackaged Antenna and
the Compact Magnetic-Mount Antenna, which mate through the
optional RF transition cable to the module’s RF connector. For more
information on the antennas, see pag e30.
2.2.3
Digital IO/Power Connector Pinout
The digital IO/Power connector pinout information is listed in
Table 2.1.
Table 2.1 J2 I/O Connector Signals
Pin number Function Description
1 TXD A Serial Port A transmit, CMOS/TTL
2 GND Ground, Power and Signal
3 RXD A Serial Port A receive, CMOS/TTL
4 PPS Pulse-Per-Second, CMOS/TTL
5 Reserve No connect
6 Reserve No connect
7 Prime Power (VCC) +3.3 VDC to
8 Battery Backup Power +2.5 VDC to
± 0.3 VDC
+ 3.6 VDC
24 Lassen SQ GPS Receiver
2.3
Power Requirements
The Lassen SQ GPS module requires +3.3 VDC ±0.3 VDC at 33 mA,
typical excluding the antenna. The on-board capacitance is 10 µF. An
important design consideration for power is the 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.
The receiver does not require any special power up or down
sequencing. The receiver power is supplied through pin 7 of the I/O
connector. See Table 2.2 for the +3.3 VDC power specifications.
Warning – The Lassen SQ GPS receiver is ready to accept TSIP
commands approximately 2.1 seconds after power -up. If a command is
sent to the receiver within this 2.1 second window, the receiver will ignore
the command. The Lassen SQ GPS receiver will not respond to
commands sent within the 2.1 second window and will discard any
associated command data.
Hardware Integration 2
Battery Back-up
The Lassen SQ GPS receiver 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 can be stored in non-volatile Flash 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 time to first fix. A 3.6 volt lithium battery used
for back-up power can last up to five years.
Lassen SQ GPS Receiver 25
2 Hardware Integration
Warning – If battery power is not present, the receiver’s power can be
turned off and then back on to force a system reset and a cold start. The
receiver should be off for no less than 3 minutes to ensure that the RAM
memory does not retain any old data due to the residual voltage from the
power supply. Alternatively, you can enter the cold start command (TSIP
Packet 0x1E) to force a system reset and a cold start. Cycle power and
issue the cold start TSIP command immediately after switching the power
back on.
Note – 2.5V is the minimum allowable battery back-up voltage. When
the battery back-up power output drops below 2.5V, the real-time clock
may not operate over the specified temperature range. This can also
significantly extend the time to first fix.
Table 2.2 Power Requirements
Signal Volt ag e Current J2 Pin #
VCC 3.0 to 3.6 33mA 7
Battery Back-up 2.5 to 3.6 19µA
(at 3.3 volts, +25°C)
Ground 0 -- 2
8
26 Lassen SQ GPS Receiver
2.4
Serial Interface
As an embedded design, the Lassen SQ GPS module provides direct
CMOS compatible TTL level serial I/O. The RX and TX signals on
the J2 I/O connector are driven directly by the UART on the Lassen
SQ GPS receiver. Interfacing these signals directly to a UART in your
application circuitry provides direct serial communication without the
complication of RS-232 or RS-422 line drivers.
Note – The serial I/O signals on J2 are TTL level. They are not
inverted or driven to RS-232 levels.
Hardware Integration 2
Lassen SQ GPS Receiver 27
2 Hardware Integration
2.5
Pulse-Per-Second (PPS)
The Lassen SQ GPS receiver provides a four microsecond wide,
CMOS compatible TTL level Pulse-Per-Second (PPS). The PPS is a
positive pulse available on pin 4 of the power and I/O connector. The
rising edge of the PPS pulse is synchronized with respect to UTC. The
timing accuracy is ±95 nanoseconds when valid position fixes are
being reported.
The rising edge of the pulse is typically less than 20 nanoseconds. The
distributed impedance of the attached signal line and input circuit can
affect the pulse shape and rise time. The PPS can drive a load up to
5mA without damaging the module. The falling edge of the pulse
should not be used. The PPS is always on (early PPS) and is driven by
the Real Time Clock (RTC) until the receiver acquires GPS time from
the satellite and is getting fixes. The PPS is output immediately after
main power is applied, and continues even if the receiver loses GPS
lock. The drift of the PPS, when the Lassen SQ GPS receiver is not
tracking satellites, is unspecified and should not be used for
synchronization.
Note – Trimble Navigation has measured better than 50 nanoseconds
accuracy on the Lassen SQ GPS receiver PPS signal in static mode.
For more information on the use of the Lassen SQ GPS module in
timing applications, contact your Trimble sales representative.
28 Lassen SQ GPS Receiver
2.6
Mounting
Hardware Integration 2
The Lassen SQ GPS PCB is encased in a metal enclosure. The
enclosure acts as a protective case. There are four mounting solder
tabs on the bottom of the enclosure. When the surface-mount mating
connector is used, the mounting tabs may be used for securing the
Lassen SQ GPS module on the user’s PCB. When the cable strip I/O
connector scheme is used, the connector side of the Lassen SQ GPS
module will be faced up and the mounting tabs will be on the top of
the module away from PCB.
The Lassen SQ GPS module can be attached to the integrator platform
by many methodologies including solder, glue, double sided adhesive
tape, and custom hold down mounts for the module's mounting tabs.
Note – See Appendix D for mechanical drawings and specifications
regarding the spacing of the mounting tabs and the dimensions of the
enclosure.
Lassen SQ GPS Receiver 29
2 Hardware Integration
2.7
GPS Antennas
The antenna receives the GPS satellite signals and passes them to the
receiver. The GPS signals are spread spectrum signals in the 1575
MHz range and do not penetrate conductive or opaque surfaces.
Therefore, the antenna must be located outdoors with a clear view of
the sky. The Lassen SQ GPS receiver requires an active antenna. The
received GPS signals are very low power, approximately -130 dBm, 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 three antennas for use with the Lassen SQ GPS receiver
described below and in Appendix D.
1. The Ultra-Compact Embedded GPS Antenna with an HFL
connector, is ideal for portable and mobile applications. This
unpackaged antenna is approximately the same size as the
module itself, and can be easily integrated into mobile
applications. This antenna is supplied with the Starter Kit (see
Figure 2.4).
2. A Compact Unpackaged Antenna with an MCX connector,
slightly larger than the ultra-compact model (see #1 above),
mates to the Hirose connector on the Lassen SQ GPS module
with an optional RF transition cable (see Figur e2.5).
3. A Compact Magnetic-Mount GPS Antenna with a 5 m cable
and an MCX connector. This antenna provides for a flexible,
movable installation. The MCX output connector mates to the
Hirose connector on the Lassen SQ GPS module with an
optional RF transition cable. This antenna is supplied with the
Starter Kit (see Figure 2.6). The MCX connector on the end of
the antenna cable mates to the MCX connector in the front of
the Starter Kit interface unit.
Warning – When magnetic-mount or permanent-mount GPS antennas
are installed on a metal surface for prolonged periods, care must be taken
to insulate the antennas in order to prevent galvanic corrosion.
30 Lassen SQ GPS Receiver
Hardware Integration 2
Figure 2.4 Ultra-Compact Embedded GPS Antenna
Figure 2.5 Compact Unpackaged GPS Antenna
Figure 2.6 Compact Magnetic-Mount GPS Antenna
Lassen SQ GPS Receiver 31
2 Hardware Integration
32 Lassen SQ GPS Receiver
CHAPTER
3
Software Interface
In this chapter:
■
Start-up
■
Communicating with the Lassen SQ GPS receiver Module
■
Port Protocol and Data Output Options
■
Custom Port Configuration
■
When prompted, select the factory default option.
3
3 Software Interface
3.1
Start-up
Lassen SQ GPS module is a complete 8-channel parallel tracking GPS
receiver designed to operate with the L1 frequency, standard position
service, Coarse Acquisition code. 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.
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, the receiver
must continuously track satellites for approximately 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 45 seconds. The
receiver will respond to commands almost immediately after power-up
(see Warning below).
Note – See Chapter 4 for further detail on ephemeris data and the
GPS almanac.
Warning – The Lassen SQ GPS receiver is ready to accept TSIP
commands approximately 2.1 seconds after power -up. If a command is
sent to the receiver within this 2.1 second window, the receiver will ignore
the command. The Lassen SQ GPS receiver will not respond to
commands sent within the 2.1 second window and will discard any
associated command data.
34 Lassen SQ GPS Receiver
Software Interface 3
3.2
Communicating with the Lassen SQ GPS receiver
Module
The Lassen SQ GPS receiver supports two message protocols: TSIP
and NMEA. Communication with the module is through a CMOS
compatible, TTL level serial port. The port characteristics can be
modified to accommodate your application requirements. Port
parameters are stored in non-volatile memory (flash) which does not
require backup power. Table 3.1. lists the default port characteristics.
3.2.1
3.2.2
Software Tools
The Software Tools provided on the Starter Kit CD-ROM include both
user friendly Windows and DOS applications to facilitate
communication with the receiver, via the Trimble Standard Interface
Protocol (TSIP). This CD also includes sample C source code and
reusable routines to aid in developing applications.
Note – The TSIP and NMEA protocols are discussed beginning on
page 37 of this chapter, and in Appendix A, Appendix B, and
Appendix C.
Port Configuration
The Lassen SQ GPS module has a single I/O port. Tabl e3.1 provides
the default protocol and port configuration for the receiver, as
delivered from the factory. TSIP IN/OUT is the default protocol.
Table 3.1 Default Protocol and Port Configuration
Input Output
Protocol Default Setup Protocol Default Setup
TSIP Baud Rate: 9600
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
Lassen SQ GPS Receiver 35
3 Software Interface
The Lassen SQ GPS receiver can also be configured to output NMEA
messages. The industry standard port characteristics for NMEA are:
• Baud Rate: 4800
• Data Bits: 8
• Parity: None
• Stop Bits:1
•No Flow Control
Any standard serial communications program, such as Windows
Hyper-Terminal or PROCOMM, can be used to view the NMEA
output messages. TSIP is a binary protocol and outputs raw binary
serial data that cannot be read when using Windows Terminal or
PROCOMM. To view the output of the TSIP protocol in text format,
use the TSIPCHAT or the SQ_Monitor program (see the CD-ROM
provided in the Starter Kit).
The serial port driver in the TSIPCHAT Tool Kit matches the Lassen
SQ GPS receiver serial port characteristics. The TSIPPRNT program
converts binary data logged with the
TSIPCHAT
program into text that
may be printed and displayed. Both of these tools are included in the
Software Developer’s Toolkit.
Warning – When using the TSIP protocol to change port assignments or
settings, confirm that your changes do not affect the ability to
communicate with the receiver (e.g., selecting the PC COM port settings
that do not match the receiver’s, or changing the output protocol to TSIP
while not using TSIPCHAT ).
36 Lassen SQ GPS Receiver
3.3
Port Protocol and Data Output Options
Software Interface 3
3.3.1
Protocol Configuration and Interface
The factory default protocol for the Lassen SQ GPS receiver is the
Trimble Standard Interface Protocol (TSIP), for both input and output.
The serial port setting is 9600 baud 8-odd-1. The receiver protocol can
be re-configured using TSIP command packet 0xBC, in conjunction
with TSIPCHAT, SQ_Monitor, or a user written serial interface
program. See Table 2 for protocol configuration options, and
Appendix A for details on the 0xBC command packet.
TSIPCHAT provides the simplest means to communicate with the
receiver using a PC (386 or higher) running either the DOS or
Windows operating systems. Responses are displayed on the computer
monitor in text format.
SQ_Monitor, a Windows-based GUI, provides a versatile graphical
interface for monitoring TSIP data. This application allows the user to
view complete receiver operations including data output, status and
configuration. In this application, the entry of command packets is
replaced by traditional point and click pull-down menus.
C source code routines for TSIPCHAT are also provided on the CD
contained in the Starter Kit. When used as software design templates,
this source code can significantly speed-up code development.
The protocol settings and options are stored in battery-backed
Random-Access-Memory (BBRAM). They can also be saved into the
non-volatile memory (Flash), if desired, using command 0x8E-26. See
to Appendix A for additional information on Flash storage for custom
operation.
Lassen SQ GPS Receiver 37
3 Software Interface
3.3.2
3.3.3
TSIP Data Output Modes
TSIP is the default protocol for the Lassen SQ GPS receiver. This
binary language offers users a wide variety of commands and reports.
TSIP enables the Lassen SQ GPS receiver to operate in two data
output modes, both available during operation. In Query Mode, packet
data is returned in response to input query packets. In Automatic
Mode, a selected group of data packets is output continuously at two
fixed rates – every second and every five seconds. The format and
ensemble of the automatic output packets is configured using packets
0x35, 0x70, and 0x8E-20 (see Appendi xA for packet details). Packet
settings are stored in BBRAM. They can also be saved in non-volatile
memory (Flash) using command packet 0x8E-26. See Appendix A for
additional information on Flash storage for custom operation.
Automatic TSIP Output Options and Defaults
Default 0x35 setting (byte 0, 1, 2, 3 = 2, 2, 0, 0):
• Position and velocity data precision: 4 byte floating point
• Position output option and format (byte 0 setting):
– Latitude – radian
– Longitude – radian
– Altitude – meters (WGS-84)
• No super-packet output (byte 0 setting)
• Velocity output option and format (byte 1 setting):
– East Velocity – meters/sec.; + for East
– North Velocity – meters/sec.; + for North
– Up Velocity – meters/sec.; + for Up
38 Lassen SQ GPS Receiver
Software Interface 3
• Time reports option and format (byte 2 setting):
– GPS (not UTC) time of week – seconds; 4 byte floating
point
– Extended GPS week number – weeks; 2 byte integer
(INT16)
– GPS UTC offset – seconds; 4 byte floating point
Default 0x70 setting (byte 0, 1, 2, 3 = 1, 1, 1, 0):
• Position-Velocity Dynamic Filter enabled
• Position-Velocity static Filter enabled
• Altitude Filter enabled
Default 0x8E-20 setting (byte 1 = 1):
3.3.4
• 0x8F-20 output is included in the super-packet for automatic
output IF packet 0x35 selects the super-packet for automatic
output options
Automatic TSIP Output Packets (fixed rate)
One second interval:
• 0x4A – (1) GPS position fix; (2) clock bias and time of fix; {20
byte format}
• 0x56 – velocity fix
• 0x6D – (1) list of satellites used for position fixes; (2) PDOP,
HDOP, VDOP; (3) fix mode
• 0x82 – DGPS position fix mode
Lassen SQ GPS Receiver 39
3 Software Interface
Five second interval:
• 0x41 – (1) GPS time of the week (seconds); (2) extended GSP
• 0x46 – health of receiver
• 0x4B – (1) Machine/Code ID; (2) Real-time-clock availability
week number; (3) GPS UTC offset(seconds)
status; (3) almanac validity status; (4) having super-packet
support status
3.3.5
Packet Output Order
After power up or a software reset (packet 0x1E), seven start-up
packets are sent, only once, by the receiver in this order: 45, 46, 4B,
4A, 56, 41, 82
Before position fixes are available, the 1 second and 5 second interval
packets are sent in this order, periodically:
• Every one second for 5 seconds: 6D, 82
• Every five seconds 41, 46, 4B
When position fixes are available, the 1 second and 5 second interval
packets are sent in this order, periodically:
• Every one second for 4 seconds: 4A, 56, 6D, 82
• Every 5 seconds: 4A, 56, 41, 46, 4B, 6D, 82
40 Lassen SQ GPS Receiver
Software Interface 3
3.3.6
NMEA 0183 Protocol and Data Output Options
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. The Lassen SQ GPS
receiver also adheres to the NMEA 0183, Version 3.0 specification.
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 SQ GPS receiver, NMEA is an output only protocol. The
NMEA protocol is described in detail in Appendix C.
The receiver is shipped from the factory with the TSIP protocol
configured on Port 1. The receiver can be reconfigured using TSIP
command packet 0xBC, in conjunction with TSIPCHAT, SQ_Monitor,
or a user written serial interface program.
The NMEA output messages selection and message output rate can be
set using TSIP command packet 0x7A. The default setting is to output
the GGA and VTG messages at a 1 second interval, when the receiver
output protocol is configured to NMEA, using packet 0xBC.
If NMEA is to be permanent for the application, the protocol
configuration (0xBC) and NMEA message output setting (0x7A) can
be stored in the non-volatile memory (on-board flash) using TSIP
command 0x8E-26.
Lassen SQ GPS Receiver 41
3 Software Interface
3.4
Custom Port Configuration
TSIPCHAT can be used to customize the Lassen SQ GPS receiver
configuration settings and to save a configuration to non-volatile
memory. The most recent port configuration is stored in BBRAM.
This eliminates the need to repeat setup each time the receiver power
is cycled. However, if the battery-backed power is accidentally lost,
the port configuration automatically resets to either what was saved in
the non-volatile memory (Flash) or to the factory default.
Tip – To ensure continuous operation, store all port configuration changes
in the non-volatile memory.
Following are step-by-step instructions for using TSIPCHAT to
customize Lassen SQ GPS receiver port configuration.
Customizing the Configuration
1. Insert the CD in the CD-ROM drive of your computer.
2. Open a DOS window and set the path to the TSIPCHAT
location.
3. To run the program, type TSIPCHAT –c1 if attached to PC
COM1, or type TSIPCHAT –c2 if attached to PC COM2.
4. Power-up the receiver. Automatic report streams should be
scrolling up in the DOS window. Assuming that your receiver is
set to the default configuration, the settings will be: 9600 baud,
8-odd-1.
Note – If data is not being output after receiver power up, use the “^i”
command in TSIPCHAT to reset the COM1/COM2 setting in PC (not
the receiver).
Tip – Entering “?” in the TSIPCHAT window displays all the available
commands and their corresponding TSIP packets.
42 Lassen SQ GPS Receiver
Software Interface 3
5. To re-configure the port settings and protocol, type “U” and
respond to the input prompts. At the end of this procedure,
select the option that resets the PC COM port to match the new
settings. Communication should resume almost immediately.
Saving the Configuration
1. Before storing the new configuration in Flash, confirm that the
receiver has been configured to the desired settings.
Warning – Record the new serial port settings. If power is lost, this will
speed-up recovery. Alternatively, the receiver can always be returned to
the default configuration.
2. To save the configuration to Flash:
– Enter “=” to access the command list page for the 0x8E
command packet.
– Enter “s”, to send the 0x8E-26 command packet.
– Communication is momentarily suspended while the
configuration is being stored in Flash.
3. To confirm that the configuration changes have been saved,
turn-off the power supply and the battery back-up for a few
minutes. Then, power-up the receiver and confirm that the
configuration changes have been retained. Alternatively, you
can use Packet 1E to command a cold start.
Note – Command packet 0x8E-26 executes storage of various types of
receiver settings in addition to the port and protocol. See Table 3.2 for
a complete list of the settings that can be stored in Flash memory.
Lassen SQ GPS Receiver 43
3 Software Interface
Returning to the Factory Settings
At any time, the receiver can be returned to the factory default
configuration, using command packet 0x1E.
1. Type “^k” to invoke the 0x1E command.
2. When prompted, select the factory default option.
Table 3.2 TSIPChat Command Settings Stored in Flash Memory
Command Packet 0x8E-26
TSIP Command ID TSIPCHAT
Keystroke
0x35 ‘O’ TSIP input/output formatting
0x70 ‘l’ Position filter controls
0x7A ‘q’ NMEA message formats and
Description TSIP Response ID
– Superpacket output (on/off)
– Position format (LLA and/or
ECEF)
– Precision (double or single)
– altitude format (MSL or HAE)
– Timetag format (GPS or UTC)
– SNR format (AMU or C/N
– Automatic pseudorange
output
– Position filter on/off
– Static filter on/off
– Altitude filter on/off
schedule
– NMEA output messages
– NMEA output interval
0x55
0
0x70
0x7B
44 Lassen SQ GPS Receiver
Table 3.2 TSIPChat Command Settings Stored in Flash Memory
Command Packet 0x8E-26 (Continued)
Software Interface 3
TSIP Command ID TSIPCHAT
Description TSIP Response ID
Keystroke
0xBB ‘p’ GPS configuration parameters
– Operating dimension
(2D, 3D,...)
– DGPS mode
– Dynamics mode
–Elevation mask
– SNR mask
–DOP mask
–PDOP switch
– DGPS correction age
0xBC ‘U’ Serial port configuration
– Protocol: input, output
– Baud, data bits, parity, stop
bits
0x8E-20 ‘= g’ Fixed point superfix control
(default = on)
0xBB
0xBC
0x8F-20
Lassen SQ GPS Receiver 45
3 Software Interface
3.5
Timing Applications
The Lassen SQ GPS receiver is an excellent source for accurate
system timing. Two examples of applications requiring accurate time
are environmental data acquisition and synchronization of
communications networks. The timing functions of the receiver are
supported by the TSIP protocol and the PPS signal. See Report Packet
41 in Appendix A for a description of the time function reports for
TSIP.
Note – GPS time differs from UTC (Universal Coordinated Time) by a
variable integer number of seconds: UTC = (GPS time) - (GPS UTC
Offset)
As of April 2002, the GPS UTC offset was 13 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.
3.5.1
The current GPS UTC offset is contained within the almanac
transmitted by the GPS system. The Lassen SQ GPS receiver must
have a complete almanac before the offset data is valid.
Extended GPS Week Number
The Lassen SQ GPS receiver outputs the Extended GPS Week
Number as the absolute number of weeks since the beginning of GPS
time or January 6, 1980. If the true GPS Week Number is desired,
ignore the extra MSBs of the Extended GPS Week Number and use
only the 10 LSBs (bytes 4 and 5 of Packet 0x41).
46 Lassen SQ GPS Receiver
CHAPTER
4
Operation and Performance
In this chapter:
Introduction
GPS Satellite Message
Satellite Acquisition and Time to First Fix
Satellite Mask Settings
Standard Operating Modes
Position Accuracy
Coordinate Systems
Performance Characteristics
GPS Timing
System Architecture
4
4 Operation and Performance
Introduction
4.1
This chapter describes the Lassen SQ GPS receiver 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 SQ GPS receiver 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 SQ GPS receiver automatically acquires new
satellites and includes them in the solution set as required.
48 Lassen SQ GPS Receiver
GPS Satellite Message
4.2
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 SQ GPS receiver
module updates its ephemeris and almanac as needed.
Operation and Performance 4
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 SQ GPS Receiver 49
4 Operation and Performance
Satellite Acquisition and Time to First Fix
4.3
4.3.1
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 SQ GPS receiver 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 predetermined 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 SQ
GPS receiver 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.
50 Lassen SQ GPS Receiver
Operation and Performance 4
4.3.2
Warm Start
In a warm-start condition the receiver has been powered down for at
least one hour but has stored a current almanac, an initial position, and
time, in memory.
When connected to an external back-up power source (battery
back-up), the Lassen SQ GPS receiver 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 SQ GPS receiver 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.
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.
4.3.3
Hot Start
A hot start strategy applies when the Lassen SQ GPS receiver 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.
Lassen SQ GPS Receiver 51
4 Operation and Performance
4.3.4
4.3.5
Garage Search Strategy
During a warm start search, the Lassen SQ GPS receiver 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.
System Reset
The Lassen SQ GPS receiver can be reset with software commands or
by cycling power. A system reset will cause the receiver to restart and
begin the satellite acquisition and tracking process again. There are
three types of system resets: soft reset, hard reset, and factory reset.
The TSIP protocol supports all three resets using the 0x1E command.
Power cycling can be used for either the soft reset or the hard reset.
A soft reset is a system restart. In a soft reset, the system will attempt
to acquire satellites using the satellite information and last position
data stored in RAM, and the time information supplied by the realtime clock. There are two ways to initiate a soft reset:
• Cycling main power while keeping the memory and the realtime clock alive with back-up power.
• Issuing Command Packet 0x25.
A soft reset is the same as a warm or hot start, if the information
contained in memory and supplied by the real-time clock is valid.
52 Lassen SQ GPS Receiver
Operation and Performance 4
A hard reset is a system restart that results in satellite acquisition
search using a default search set. Any data contained within RAM
memory is discarded and the real-time clock is re-initialized. Even if
back-up power is supplied, the information from memory and the realtime clock is not used. There are two ways to initiate a soft reset:
• Issuing the 0x1E command with a value of 0x4B.
• Cycling power without back-up power applied. Using this
method, power must be removed for at least 3 minutes to ensure
any residual memory storage is erased. If power is cycled
rapidly, the 0x1E command with a value of 0x4B must then be
issued to the receiver 2.5 seconds after power is restored to
ensure a hard reset.
A factory reset is used to restore all the factory default settings into the
receiver. Any user settings stored in Flash memory will be erased.
Issuing the 0x1E command with a value of 0x46 will initiate a factory
reset.
Lassen SQ GPS Receiver 53
4 Operation and Performance
Satellite Mask Settings
4.4
Once the Lassen SQ GPS receiver 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 SQ GPS receiver
are listed in Table 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 SQ GPS receiver 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
Appendix A for details on key setup parameters.)
Table 4.1 Satellite Mask Settings
Mask Setting
Elevation 5°
SNR 3
PDOP 12
PDOP Switch 6
54 Lassen SQ GPS Receiver
Operation and Performance 4
4.4.1
4.4.2
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.
SNR Mask
Although the Lassen SQ GPS receiver 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 low-elevation satellites were discussed above. In
mobile applications, the attenuation of signals by foliage is typically a
temporary condition. Since the Lassen SQ GPS receiver can maintain
lock on signals with SNRs as low as 0, it offers excellent performance
when traveling through heavy foliage.
Lassen SQ GPS Receiver 55
4 Operation and Performance
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. Multireflected signals tend to be weak (low SNR value), since each
reflection attenuates the signal. By setting the SNR mask to 3 or
higher, the impact of multi-reflected signals is minimized.
4.4.3
4.4.4
DOP Mask
Position Dilution of Precision (DOP) 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 DOP and will contribute to a lower position accuracy.
For most applications, a DOP mask of 12 offers a satisfactory trade-off
between accuracy and GPS coverage time. With world-wide GPS
coverage now available, the DOP mask can be lowered even further
for many applications without sacrificing coverage.
PDOP Switch
The default positioning mode for the Lassen SQ GPS receiver is
Automatic. In this mode, the receiver attempts to generate a 3dimensional (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.
Note – PDOP Switch is only used in Auto mode.
56 Lassen SQ GPS Receiver
Standard Operating Modes
4.5
The tracking mode controls the allocation of the receiver's tracking
channels and the method used for computing position fixes.
Operation and Performance 4
4.5.1
Fix Modes
The Lassen SQ GPS receiver offers three positioning modes: 2D
Manual, 3D Manual, and Automatic 2D/3D. Automatic 2D/3D is the
default mode for the Lassen SQ GPS receiver. The positioning mode
can be modified in receivers accepting TSIP commands. (See
Appendix A for more information on the TSIP protocol.)
2D ManualLassen SQ GPS Receiver
In 2D Manual mode, the Lassen SQ GPS receiver 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 zero 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).
3D Manual
In 3D Manual mode, the Lassen SQ GPS receiver 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 SQ GPS receiver will suspend position data
outputs.
Lassen SQ GPS Receiver 57
4 Operation and Performance
2D/3D Automatic
The default operating mode for the Lassen SQ GPS receiver is 2D/3D
Automatic. In this mode, the Lassen SQ GPS receiver 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 SQ GPS receiver
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.
Position Accuracy
4.6
GPS position accuracy is degraded by atmospheric distortion, satellite
geometry, satellite clock errors, and receiver clock errors. 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.
58 Lassen SQ GPS Receiver
Coordinate Systems
4.7
Once the Lassen SQ GPS receiver 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 or NMEA protocol, as determined by the settings of the receiver.
These protocols are defined in the Appendices. To change from one
protocol to another, see Appendix A.
Operation and Performance 4
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-84 ellipsoid. 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.
Lassen SQ GPS Receiver 59
4 Operation and Performance
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. UTC time replaced GMT
(Greenwitch Mean Time) as the world standard, in 1986.
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 13 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.
4.7.2
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.
60 Lassen SQ GPS Receiver
Performance Characteristics
4.8
Operation and Performance 4
4.8.1
4.8.2
Update Rate
The Lassen SQ GPS receiver computes and outputs position solutions
once per second, on the second. NMEA outputs can be scheduled at a
slower rate using TSIP command 0x7A (see Appendix A).
Dynamic Limits
The dynamic operating limits for the Lassen SQ GPS receiver 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 SQ GPS Receiver Operating Limits
Operation Limit
Acceleration 4 g (39.2 m/s
Jerk 20 m/s
Speed 500 m/s
2
)
3
Altitude 18,000 m
Note – The Lassen SQ GPS Receiver firmware contains an algorithm
that allows either the speed limit or altitude limit to be exceeded, but
not both. This allows the receiver to be used in high altitude (research
balloon) applications without a special factory configuration.
Lassen SQ GPS Receiver 61
4 Operation and Performance
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.
62 Lassen SQ GPS Receiver
GPS Timing
4.9
Operation and Performance 4
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 SQ GPS receiver 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 ±95 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.
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 SQ GPS receiver clocking rate is 3.126 MHz. This rate
corresponds to a steering resolution of ±160 ns.
Lassen SQ GPS Receiver 63
4 Operation and Performance
4.9.1
4.9.2
Serial Time Output
Both the TSIP and NMEA protocols include time messages. See Report
Packet 41 in Appendix A for a description of the time reports for each
protocol.
Note – GPS time differs from UTC (Universal Coordinated Time) by a
variable, integer number of seconds UTC=(GPS time)-(GPS UTC offset).
As of April 2002, the GPS UTC offset was 13 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.
Pulse-Per-Second (PPS)
The Lassen SQ GPS receiver provides a four microsecond wide, CMOS
compatible TTL level Pulse-Per-Second (PPS). The PPS is a positive pulse
available on pin 4 of the Lassen SQ GPS receiver power and I/O
connector. The rising edge of the PPS pulse is synchronized with respect
to UTC. The timing accuracy is ±95 nanoseconds when valid position
fixes are being reported.
The rising edge of the pulse is typically less than 20 nanoseconds. The
distributed impedance of the attached signal line and input circuit can
affect the pulse shape and rise time. The PPS can drive a load up to 5mA
without damaging the module. The falling edge of the pulse should not be
used. The PPS is always on (early PPS) and is driven by the Real Time
Clock (RTC) until the receiver acquires GPS time from the satellite and is
obtaining fixes. The PPS is output immediately after main power is
applied, and continues even if the receiver loses GPS lock. The drift of the
PPS, when the Lassen SQ GPS receiver is not tracking satellites, is
unspecified and should not be used for synchronization.
Note – Trimble Navigation has measured better than 50 nanoseconds
accuracy of the Lassen SQ GPS receiver PPS signal in static mode. For
more information on timing applications, contact your Trimble sales
representative.
64 Lassen SQ GPS Receiver
System Architecture
4.10
The Lassen SQ GPS receiver (see Figur e4.3) 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 Lassen SQ GPS receiver receives the amplified GPS satellite
signals through the antenna feed line connector and 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.
Operation and Performance 4
Lassen SQ GPS Receiver 65
4 Operation and Performance
32.768kHz
3.3V
Antenna
Protect and
Monitor
TxA
1
RxA
3
PPS
4
8 CH DSP +
3.3V
Vback
8
Vbat
32 bit Microprocessor
XCLK
3.3V
Gnd
2,5,6
7
Data
Addr
VSTBY
POWMON
256k x 16
ROM
Reset
Generator
Vbat
3.126MHz
Sampling Clock
Q_OUT
Active L1
Antenna
I_OUT
RF
RF
Trap
SAMP_IN
RF
Connector
CLK_out
RF ASIC
PLL
Loop Filter
Figure 4.3 Lassen SQ GPS receiver Block Diagram
XTAL1
12.504MHz
TCXO
Linear
Regulator
3.3V
Q
LPF
I
LPF
Baseband Filter
66 Lassen SQ GPS Receiver
APPENDIX
A
Trimble Standard Interface
Protocol (TSIP)
The Trimble Standard Interface Protocol (TSIP) provides the system
designer with over 20 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 pag e70 will help you determine which
packets apply to your application. For those applications requiring
customization see Customizing Receiver Operations, page 71 for a
detailed description of the key setup parameters. Application
guidelines are provided for each TSIP Command Packet, beginning on
page 84.
A
A Trimble Standard Interface Protocol (TSIP)
Interface Scope
A.1
The Trimble Standard Interface Protocol is used extensively in
Trimble 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 SQ GPS receiver has one serial I/O communications port.
This port is a bi-directional control and data port utilizing Trimble
Standard Interface Protocol (TSIP). This port may also be used to
receive TSIP commands and to output industry standard ASCII-based
NMEA messages. The data I/O port characteristics and other options
are user programmable and can be stored in non-volatile flash
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.
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.
68 Lassen SQ GPS Receiver
Packet Structure
A.2
TSIP packet structure is the same for both commands and reports. The
packet format is:
Where:
Trimble Standard Interface Protocol (TSIP) A
<DLE> <id> <data string bytes> <DLE> <ETX>
•
•
<DLE>
<ETX>
is the byte 0x10
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>
('stuffing'). These extra
byte in the data string is preceded by an extra
<DLE>
<DLE> <ID>
bytes must be added ('stuffed') before
<DLE> <ETX>
and
, every
<DLE>
byte
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:
• UINT8 = Byte: An 8 bit unsigned integer.
• UINT16 = Word: A 16 bit unsigned integer.
•INT16 = I
• INT32 = Long: A 32 bit integer.
• UINT32 = ULong: A 32 bit unsigned integer.
• 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.
nteger:
A 16 bit integer.
Lassen SQ GPS Receiver 69
A Trimble Standard Interface Protocol (TSIP)
Automatic Output Packets
A.3
The Lassen SQ GPS receiver receiver 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
Output Packet ID Description Reporting
Interval
0x41 GPS time 5 seconds
0x42, 0x83, 0x4A, 0x84,
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 fault
0x6D all-in-view satellite selection, DOPs, Fix Mode 1 second
0x82 DGPS position fix mode (only in DGPS mode) 1 second
position (choose packet with I/O options) 1 second
5 seconds
detect)
70 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
Customizing Receiver Operations
A.4
For information on customizing receiver operations, see the following
tables on selecting report data.
Automatic Position and Velocity Reports
A.5
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.2 Packet 35: Automatic Position and Velocity Reports Control Setting Bits
Packet 0x35, Byte 0 Packet 0x35, Byte 1
Report
Packet ID
Description
Bit 0 Bit 1 Bit 4 Bit 5 Bit 0 Bit 1
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) 1
0x8F-20 LLA and ENU 1
10
11
1
(default)
11
0
1
(default)
Lassen SQ GPS Receiver 71
A Trimble Standard Interface Protocol (TSIP)
Initialization Packets to Speed Start-up
A.6
If 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.
Table A.3
Input Byte Description
0x2B initial position
0x2E initial time
0x38 almanac (for each SV)
0x38 almanac health
0x38 ionosphere page
0x38 UTC correction
72 Lassen SQ GPS Receiver
Packets Output at Power-Up
A.7
The following table lists the messages output by the receiver at powerup. 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 as listed in the table
below. After Packet 82 is output, the sequence is complete and the
receiver is ready to accept commands.
Table A.4 Packet Power-up Output Messages
Output ID Description Notes
0x45 software version --
0x46 receiver health --
0x4B machine code/status --
Trimble Standard Interface Protocol (TSIP) A
As chosen, see Table A.3
default: 0 x 4A, 0 x 56
0x41 GPS time
82 DGPS position fix mode --
Timing Packets
A.8
If you are using the Lassen SQ GPS receiver as a timing system, you
may need to implement the following TSIP control commands.
Table A.5 Timing Packet TSIP Control Commands
Input ID Description Output ID
0x21 get the current GPS time 0x41
0x38-05 request UTC parameters 0x58-05
position/Velocity output As chosen, see
Ta b l e A . 3 .
Lassen SQ GPS Receiver 73
A Trimble Standard Interface Protocol (TSIP)
Satellite Data Packets
A.9
The following packets contain a variety of GPS satellite data.
Table A.6 Satellite Data Packet Data I/O Descriptions
Input ID Description Output ID
0x27 request signal levels 0x47
0x38 request/load satellite system data 0x58
0x3C request tracking status 0x5C
Backwards Compatibility
A.10
TSIP packets implemented in the Lassen SQ GPS receiver are
backward compatible with those used in Lassen SK II GPS receiver.
For information regarding compatibility with other Trimble receivers,
contact the Trimble Technical Assistance Center.
74 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
Recommended TSIP Packets
A.11
Table A.7 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)
Navigation GPS time 0x21 0x41
position & velocity (superpacket) 0x8E-20 or
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
query receiver state (health) 0x26 0x46,
query current satellite selection 0x24 0x6D
query signal levels 0x27 0x47
query satellite information (azimuth,
elevation, etc.)
0x35 0x55
0x8F-20
0x37 or
auto
0x4B
0x3C 0x5C
GPS System query/load GPS system data 0x38 0x58
query receiver ID & error status 0x26 0x4B,
0x46
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) 0xBB 0xBB
Lassen SQ GPS Receiver 75
A Trimble Standard Interface Protocol (TSIP)
Table A.7 (Continued)Recommended TSIP Packet Data
Function Description Input Output
Initialization full reset (clear battery backup 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
Command Packets Sent to the Receiver
A.12
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 84.
0x1E
Table A.8 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
0x2A altitude for 2-D mode 0x4A
76 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
Table A.8 User-Selected Command Packet Options (Continued)
Input ID Packet Description Output ID
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
0x3C tracking status 0x5C, see Note 2
0x70 filter configuration 0x70
0x7A set/request NMEA output configuration 0x7B
0xBB set receiver configuration 0xBB
0xBC set port configuration 0xBC
0x8E-20 last fix with extra information (fixed point) 0x8F-20
0x8E-26 Store settings in Flash memory. 0x8F-26
Note 1 – Output is determined by packet 0 x 35. See Tabl eA.4 to
determine which messages are output at power-up.
Note 2 – No response sent if data is not available.
Lassen SQ GPS Receiver 77
A Trimble Standard Interface Protocol (TSIP)
Report Packets Sent by the Receiver to the User
A.13
The table below summarizes the packets output by the receiver. The
response packets may depend on user-selected options. These
selections are described on page84.
Table A.9 User-Selected Report Packet Options
Output ID Packet Description Input ID
0x41 GPS time 0x21, auto
0x42 single-precision XYZ position 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
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
0x56 velocity fix (ENU) 0x37, auto
0x57 information about last computed fix 0x37
0x58 GPS system data/acknowledge 0x38
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
0x8F-20 last fix with extra information (fixed point) auto, 0x37, 0x8E-20
0xBB GPS navigation configuration 0xBB
0xBC Receiver port configuration 0xBC
78 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
Key Setup Parameters or Packet BB
A.14
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.10 Setup Parameters in Packet 0xBB
Parameter Accuracy Fixes Factory Default
Fix mode Man 3D AUTO AUTO
Dynamics code Land Land Land
Elevation mask 10° 5° 5°
Signal mask 6.0 4.0 3.0
DOP mask 6.0 12.0 12.0
DOP switch NA 8.0 6.0
DGPS correction age 10 Seconds N/A 30 Seconds
The default values in Table A.10 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.
Lassen SQ GPS Receiver 79
A Trimble Standard Interface Protocol (TSIP)
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.14.1
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 2D/3-D, where the receiver first attempts to obtain a 3-D solution with a
PDOP below the 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.
80 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
When using the 2-D mode, expect fixes with accuracies which are at
best as accurate as the supplied altitude. If a marine user enters sealevel 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.14.2
A.14.3
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.
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 SQ GPS Receiver 81
A Trimble Standard Interface Protocol (TSIP)
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.14.4
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 3 (AMU). 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.
82 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
A.14.5
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.
Lassen SQ GPS Receiver 83
A Trimble Standard Interface Protocol (TSIP)
Packet Descriptions
A.15
A.15.1
Command Packet 0x1E - Clear Battery Backup, then Reset
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.
Table A.11 Command Packet 0x1E Format
Byte Item Type Value Definition
0Reset
mode
Warning – All almanac, ephemeris, current position, mode, and
communication port setup information is lost when executing the “Factory
Reset” command. In normal use this packet should not be sent.
Warning – 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 near-instantaneous recuperation by the receiver
in case of power loss or clearing of battery-backed memory by using the
TSIPCHAT command “@” to load it back into the receiver memory.
Unit 8 0x4B
0x46
Cold start: Erase BBRAM and
restart
Factory reset: Erase BBRAM and
Flash and restart
84 Lassen SQ GPS Receiver
Trimble Standard Interface Protocol (TSIP) A
A.15.2
A.15.3
A.15.4
Command Packet 0x1F - Request Software Versions
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
0x
45.
Command Packet 0x21 - Request Current Time
This packet requests current GPS time. This packet contains no data.
The GPS receiver returns Packet
0x
41.
Command Packet 0x23 - Initial Position
(XYZ Cartesian ECEF)
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 about 1,000 miles since 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.
Note – To initialize using the Latitude-Longitude-Altitude
representation, use Command Packet
Table A.12 Command Packet 0x23 Data Format
Byte Item Type Units
0-3 X Single Meters
4-7 Y Single Meters
8-11 Z Single Meters
2B.
0x
Lassen SQ GPS Receiver 85
A Trimble Standard Interface Protocol (TSIP)
A.15.5
A.15.6
A.15.7
Command Packet 0x24 - Request GPS Receiver Position
Fix Mode
This packet requests current position fix mode of the GPS receiver.
This packet contains no data. The GPS receiver returns Packet
0x
6D.
Command Packet 0x25 - Initiate Soft Reset & Self Test
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.4). The GPS receiver sends Packet
on power-up and reset (or on request); thus if Packet
0x
0x
45 appears
45 only
unrequested, then either the GPS receiver power was cycled or the
GPS receiver was reset.
Command Packet 0x26 - Request Health
A.15.8
A.15.9
This packet requests health and status information from the GPS
receiver. This packet contains no data. The GPS receiver returns
Packet
0x
46 and 0x4B.
Command Packet 0x27 - Request Signal Levels
This packet requests signal levels for all satellites currently being
tracked. This packet contains no data. The GPS receiver returns
Packet
0x
47.
Command Packet 0x2A - Altitude for 2-D Mode
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 (see page 92).
86 Lassen SQ GPS Receiver
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