Explore Scientific PMC-Eight ESOGT-01B Programmer's Reference Manual

PMC-Eight™

Programmer’s

Reference

DOC-ESPMC8-002 Release 2 2019_March 07

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Revised by: Jerry Hubbell, Vice President Engineering, Explore Scientific, LLC. Reviewed by: Alex Sanchez, Director Quality Explore Scientific, LLC. Reviewed by: Dan Dickerson, APh Technological Consulting Approved by: Scott Roberts, President Explore Scientific, LLC.

NOTE: This document is provided to our PMC-Eight™ customers for their personal use in developing applications for the PMC-Eight™ Control System in accordance with the requirements of Explore Scientific and the PMC-Eight™ OpenGOTO™ Community Steering Committee.

If you have any comments or questions about this document, please contact:

Attn: Vice President of Electrical Engineering Explore Scientific, LLC 1010 South 48th Street Springdale, AR 72762 (866) 252-3811

The PMC-Eight™ and OpenGOTO™ Name and Logo are registered trademarks of Explore Scientific, LLC, All Rights Reserved. The JingHua Optical Corporation (JOC) located in Guangzhou, China is the parent company of Explore Scientific.

Propeller™ copyright Parallax, Inc. SBIG ST-4 standard copyright Santa Barbara Instruments Group, Cyanogen, LLC. RN-131 module copyright Microchip, Inc. ESP-WROOM-02 (ESP8266) module copyright Espressif, LLC. G-11 mount copyright Losmandy Astronomical Products, Hollywood General Machining, Inc. PHD2 copyright Open PHD Guiding Project.

This is the third in the following series of documents for the PMC-Eight™ System:

Document Number Title DOC-ESPMC8-001A PMC-Eight™ Owner’s Reference Manual (Customer Use) DOC-ESPMC8-001B iEXOS 100 PMC-Eight™ Owner’s Reference Manual (Customer Use) DOC-ESPMC8-002 PMC-Eight™ Programmer’s Reference (Customer Use) DOC-ESPMC8-003 PMC-Eight™ JOC Command Language Reference (Internal Use) DOC-ESPMC8-004 PMC-Eight™ Datasheet and Design Basis Document (Internal Use) DOC-ESPMC8-005 PMC-Eight™ Firmware and Software Design Reference (Internal Use) DOC-ESPMC8-006 PMC-Eight™ Firmware and Software Flowcharts (Internal Use Only) DOC-ESPMC8-007 PMC-Eight™ Hardware Reference Schematics and Datasheets (Internal Use)

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Document Notes

Revision History

0.0 GRH DRAFT Initial Draft.

0.1 GRH DRAFT Added Sections VI and VII.

0.2 GRH DRAFT Revised Section V to add “ESR!” Communications Reset command.

0.3 GRH DRAFT Revised Section III to correct and expand on Meridian Flip discussion.

1.0 GRH RELEASE 0 Miscellaneous cleanup of text and sections for release.

1.1 GRH RELEASE 1 Revised Section II to add board layout information and LED and test point information. Miscellaneous revisions and formatting changes.

1.2 GRH RELEASE 2 Revised Sections II–VIII to add information about the iEXOS 100 mount and other updates. Added Appendix section for miscellaneous information, including Application Notes. Miscellaneous cleanup of text.

This document uses the following convention for units of measure. Instead of stating: 30 counts/second or 20 arc-sec/count, or 20 arc-sec per count, the units are stated as: 30 counts sec-1 or 20”arc count-1. The superscript -1 indicates that the unit is in the denominator. You will see , ‘, and “ for degrees, minutes, and seconds for angular values.

Motor count values are stated in decimal (115200) and hexadecimal (0x9C40) notation. The terms counts and microsteps are synonymous depending on the usage. All the values returned by the controller are hexadecimal strings such as “1F92CA”. Actual commands are shown in Courier New font with quotes around the command string, i.e., “ESGp0!”. Do not include the quotes when typing the commands at a terminal connected to the controller. Program names used to communicate with the PMC-Eight™ are designated in Bold Italic, i.e., Parallax Serial Terminal.

The PMC-Eight™ Control System is warranted by Explore Scientific, LLC. If you have any questions or issues when using this reference with your PMC-Eight™ system, you should contact Explore Scientific Customer Support at +1 (866) 252-3811

CAUTION: BOARD FAILURE INDUCED THROUGH PROBING THE CIRCUITRY IS NOT COVERED UNDER THE

PMC-Eight™ LIMITED WARRANTY.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Table of Contents

Document Notes 2 Table of Contents 3 Glossary 3

Acronyms 4 I. Introduction 5 II. System Description 6 III. PMC-Eight™ Controller and Command Language

Theory of Operation 13 IV. PMC-Eight™ ASCII Command Language 20 V. PMC-Eight™ ASCII Command Language Syntax 22 VI. PMC-Eight™ Hardware Interface Specifications 32 VII. PMC-Eight™ System Software Development Kit Information 33 VIII. Miscellaneous System Information 34 IX. Appendices 35

Application Note AN001: Firmware Update Procedure 36

Application Note AN002: Model 2A Switching Communications 39

Application Note AN003: Model 1A Switching Communications 44

Model 2A Analog Autoguider (ST4) Port Calibration Procedure 50

ASCOM Platform Conformance Test – PMC-Eight™ ASCOM Driver 55

Glossary

Axis—The rotational axis that the motor is driving, either RA or DEC. Right Ascension (RA)—The rotational axis that parallels the Earth’s rotational axis. Declination (DEC)—The rotational axis that allows the scope to move north or south. German Equatorial Mount (GEM)—A type of mount that positions the telescope to move on one axis to

counteract the rotation of the Earth.

Hexadecimal—The base 16 number system using characters “0” through “9” and “A” through “F”. Decimal—The normal base 10 number system used in everyday life using characters “0” through “9”. Rate—The rotational speed at which the motors are driving the mount. Position—The number of microsteps the motor has moved since startup. Direction—The direction of the motor rotation (clockwise, or counterclockwise) when looking at the

shaft end. Tracking Rate—The precision rotational speed of the RA axis motor at a very slow rate. Used to counteract the rotation of the Earth. Tracking—The act of counteracting the rotation of the Earth to keep an object in the center of the telescope field-of-view (FOV). North Celestial Pole (NCP)—The point in the Celestial Sphere where the Earth’s rotational axis points in the Northern Hemisphere. Likewise, with the South Celestial Pole (SCP) in the Southern Hemisphere. Firmware—The computer instructions installed in the permanent memory of the processor that communicate directly with the hardware I/O on the system. The firmware is compiled on an external computer and uploaded via the serial RS232(DB9)/USB communications port. RS232—A communications hardware standard for serial communications.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Acronyms

DEC Declination EpW East Pointing West FOV Field-of-View GEM German Equatorial Mount HA Hour Angle HMI Human-Machine Interface I/O Input/Output JOC Jinghua Optical Corporation LDO Low Drop Out LMST Local Mean Sidereal Time NCP/SCP North Celestial Pole/South Celestial Pole OTA Optical Tube Assembly PMC Precision Motion Controller PMGR Programmer RA Right Ascension TCP Transmission Control Protocol UDP User Datagram Protocol WpE West Pointing East

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

I Introduction

The Explore Scientific PMC-Eight™ Controller Programmer’s Reference contains the information needed to understand the controller operation and to communicate and use the base controller command language. This document contains the system description and other data that can be used to create programs to control the PMC-Eight™. More information about the PMC-Eight™ controller can be found on the Explore Scientific website at ExploreScientificUSA.com. Additional information is included in the Application Notes available on the PMC-Eight™ webpage and in Section VIII: Appendices of this document.

One of the key elements of the PMC-Eight™ System is the Explore Scientific PMC-Eight™ Command Language. This language is designed to be both flexible and powerful enough to instruct the controller to perform any task the controller can perform. This language is different from most mount controller languages in that it does not contain astronomy or telescope mount specific commands. This language contains more generic motion control commands that enable the user to quickly learn and use the system. The PMC-Eight™ System also has a built-in JOC Command Interpreter used by the OpenGOTO™ Explore Stars App available at the Microsoft App Store, Google Play Store, and Apple App Store.

The PMC-Eight™ architecture was driven by the design philosophy of abstracting the astronomical functions from the hardware/firmware layer and encapsulating them within the software driver/application layer. This provides several benefits to the overall performance, reliability, and operation of the control system. The system architecture is very similar to other industrial motion control systems that are used for single and multiple motor control functions used in robotics, power plants, and manufacturing facilities.

The model 2A circuit board design includes several features that contribute to the reliability and thermal performance of the control system, including:

• Simple three-layer circuit assembly design with an internal ground-plane used as the system

electrical common and as a thermal heat sync. This design helps evenly distribute the heat from the components throughout the board and out through the DB9 connectors and the all-aluminum enclosure. The on-board LDO voltage regulators also provide a source of heat when operating in very cold temperatures < 5F (< -15C).

• Electronic components are widely distributed on a single side of the circuit assembly to minimize

the chance of defects arising during manufacturing that could occur when placing components on both top and bottom layers of the circuit board. This also contributes to the even distribution of heat throughout the circuit board assembly.

• Wide circuit traces are used to maximize the conductivity between component pins and minimize

the voltage drop between components. This considerably reduces the amount of heat generated when power from the on-board voltage regulators is delivered to the high-current motor driver and motors. This greatly contributes to the long expected lifetime of the Model 2A.

• A conformal coating is applied to both sides of the completed circuit board assembly to create a

moisture barrier that protects the components from degradation due to moisture when operating in high-humidity environments coupled with large temperature changes.



Most of these features are not included in the PMC-Eight™ Model 1A used in the iEXOS 100 mount.

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II System Description

The PMC-Eight™ is a high-precision stepper motor controller that very accurately controls the pointing and tracking of a telescope mount. The design basis for this “industrial strength” Precision Motion Controller (PMC) includes features to increase the reliability and flexibility of the system. The PMC-Eight™ model 2A includes several electrical and thermal design features and characteristics that provide plenty of margin to ensure a long product lifetime in terms of individual assembly performance in the field, and in the life-cycle of the design. The model 1A includes a basic level of thermal design features that help to distribute and dissipate the heat generated in the system. Additional design elements incorporated in the model 1A and 2A firmware take full advantage of the deterministic processing inherent in the processor architecture to prevent complete system lockups. The system is designed to fail gracefully. While individual functions of the system may fail due to external factors, the whole system should not experience the lockups that other interrupt driven system may experience.

The microcontroller selected is a unique multi-processor design that uses eight processors, all working as independent units and communicating through shared global memory. Each of these processors is deterministic in its operation and DOES NOT use interrupts. This ensures that the task assigned to each processor runs independently, and any failure of any one task does not cause a cascading failure in any of the other processors; the result is a system that is designed to keep running even with a partial shutdown of the processor. For more information about the operation of the Parallax Propeller™ Microprocessor Chip, download the Propeller™ Datasheet . Note that both the model 2A and 1A use the same components and have nearly identical schematics.

Parallax Propeller™ P8X32A 8-Processor Architecture/Block Diagram

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Both the PMC-Eight™ model 2A and 1A use the same components and have nearly identical schematics.

PMC-Eight™ Controller Model 2A-06B

Component

Part Number

Description

1(ea) Microcontroller

Parallax P8X32A-Q44

Propeller 8-CPU Microcontroller

1(ea) 8x64k Memory

Microchip AT24C512C

EEPROM Firmware & Storage

2(ea) Motor Driver

Texas Instruments DRV8835

Stepper Motor Driver Chip

1(ea) 2A-06B WiFi Module

Microchip RN-131G

WiFi Module

1(ea) 1A-01C WiFi Module

Espressif ESP8266

ESP-WROOM-02 WiFi Module

1(ea) 1A-01C USB

FTDI FT232RL

USB Serial Interface Chip

PMC-Eight™ Major Component List

PMC-Eight™ Controller Model 1A TOP

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

PMC-Eight™ Controller Model 1A BOTTOM

The PMC-Eight™ system consists of several components and is designed to interface with the Host Computer in several different ways. The primary interface to the PMC-Eight™ Model 2A-06B is through a dedicated RS-232 interface (DB-9 connector) that serves both as the programmer’s (PGMR) interface for loading updated firmware into the system and as the interface for sending data request commands and receiving data. The primary interface to the PMC-Eight™ Model 1A-01C is through a dedicated mini-USB

type B connector that serves both as the programmer’s (PGMR) interface for loading updated firmware

into the system and as the interface for sending data request commands and receiving data. A wireless network interface (Wi-Fi) is available also for sending data request commands and receiving data. This wireless interface is the primary HMI interface for the OpenGOTO™ Explore Stars application available for the Microsoft Windows OS, Google Android OS, and Apple iOS. For details, see Section VII, Miscellaneous Programming Application Notes. The controller communicates at 115,200 BAUD with No Parity, 8 Bits, 1 Stop Bit over the network, through the RS232 connection and the USB connection.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

PMC-Eight™ System Boot Up

When the PMC-Eight™ system boots up, if you are connected to it via the wired PGMR/Serial port, you will see the following displayed on the Parallax Serial Terminal:

-------------------------------------------------------------

------------------------------------------------------------ PPPPPPP MM MM CCCCCCCC 88888 PP PP MMM MMM CC 88 88 PPPPPPP MM M M MM CC XXXXX 888 PP MM M M MM CC 88 88 PP MM MM MM CCCCCCCC 88888

------------------------------------------------------------Copyright 2013-2018 Explore Scientific LLC., Gerald R Hubbell 1010 South 48th Street, Springdale, AR 72762 PMC-Eight Support 1-866-252-3811 http://www.explorescientificusa.com

------------------------------------------------------------Portions of FIRMWARE covered by MIT LICENSE terms

------------------------------------------------------------Explore Scientific PMC-Eight Controller - Startup Initializing PMC-Eight Model 1A-01C-FW10B1a 10 AUGUST 2018... CONFORM TEST VERSION - COMMUNICATIONS TIMEOUT DISABLED

------------------------------------------------------------EEPROM Memory Test - Basic MEM_TEST1:F0F0F0F0 MEM_TEST2:0F0F0F0F MEM_TEST3:F0F0F0F0 MEM_TEST4:0F0F0F0F MEM_TEST5:F0F0F0F0

----------------------------------------------------------Command Processor Started JOC Controller Command Set: Enabled PMC-Eight Diagnostic Command Set: Enabled PMC-Eight ES Command Set: Enabled System Initialized!

------------------------------------------------------------BAUD Rate Value: P0 115200 Assigned SSID: PMC-Eight-280D Communications Channel - Enabled: P1 Serial WiFi Protocol - Disabled: P2 UDP/IP Assigned WiFi Channel Number: 7 ST4 port Sidereal Rate Fraction: P3 40 Unused Value: P4 0 Unused Value: P5 0 Unused Value: P6 0 Unused Value: P7 0 Unused Value: P8 0 Unused Value: P9 0

-------------------------------------------------------------

PMC-Eight™ Boot-Up Splash Screen

After the copyright information is displayed on the PMC-Eight™ boot splash screen, the current firmware version installed in the controller is displayed. You can also use the “ESGv!” command to obtain the current firmware version. The bottom portion of the PMC-Eight™ boot splash screen shows you the current configuration of parameters P0–P9. The ones to make note of include P1-Communications Channel, P2-WiFi Protocol, and the value of the Assigned WiFi Channel Number.

Updating/Restoring/Loading Firmware

The firmware on the PMC-Eight™ model 1A and 2A can be updated via the PGMR/Serial port. The document Explore Scientific PMC-Eight™ Application Note PMC8-AN001: How-To Update the PMC- Eight™ Control System Firmware (located in the Appendices) explains this process. The firmware files are in a Knowledge Base Article on the Explore Scientific USA website, just search for “firmware” in the Knowledge Base search tool.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Board Status Indicator LEDs

The model 2A-06B and model 1A-01C PMC-Eight™ processor boards have two LEDs; the RED LED (6) is ON when power is applied to the board. The GREEN LED (3) is ON indicating the processor status after the processor firmware boots up and active communications are going on with the processor, and the watchdog process is active monitoring the communications.

PMC-Eight™ Model 2A-06B Status LEDs

The model 2A-06B PMC-Eight™ RN-131 daughter board has four LEDs; The YELLOW LED (1) is FLASHING when there is data transmission between the PMC-Eight™ and the host computer application—either the ExploreStars application or the ASCOM Driver. The RED LED (5) is the WiFi association status and flashes until a connection to the model 2A-06B SSID (PMC-Eight-xx) of the PMC-Eight™ is made by the host computer. The GREEN LED (2) is ON when power is applied to the daughter board from the main board. The GREEN LED (4) FLASHES FAST when a connection is ACTIVE. LED (4) FLASHES SLOW when the module is waiting on a connection. The model 1A-01C PMC-Eight™ uses the Espressif ESP-WROOM-02 (ESP8266) WiFi module for wireless communications. There are no communications status lights provided on that version of the PMC-Eight™.

Switching PMC-Eight™ Communications Channels

You can use the document Explore Scientific PMC-Eight™ Application Note PMC8-AN002: Connecting to the PMC-Eight™ with a Terminal Program to Configure the RN-131 WiFi Interface and Switching Between the WiFi Interface and the Serial Interface, and the document Explore Scientific PMC-Eight™ Application Note PMC8-AN003: Switching Between the WiFi Interface and the Serial Interface on the

iEXOS 100™ Mount Controller (available in the Appendix at the end of this document) to switch the communications channel from WiFi (UDP/TCP) to Serial and back again.

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Model 2A Circuit Test Points

WARNING: Prior to opening the PMC-Eight™ enclosure, ensure that you are familiar with all

applicable electrical safety procedures as they apply to working on low-voltage DC circuits. Circuit failure may occur if proper procedures are not followed when probing the circuitry. See this extensive discussion on Electrical Safety.

CAUTION: BOARD FAILURE INDUCED THROUGH PROBING THE CIRCUITRY IS NOT COVERED UNDER

THE PMC-Eight™ LIMITED WARRANTY.

There are several test points on the model 2A-06B circuit board assembly (indicated below with a black triangle) labeled TP_XXXX, such as: TP_GND, TP_VDD, TP_10V-1, TP_10V-2, and TP_5V. There are also test points to measure the reference voltages for the current limits and the ST4 port frequency and stepper motor pulses. Headers on the assembly provide access to the RS-232 signals, the power supply voltages (3.3 Vdc, 5.0 Vdc, 10.0 Vdc, and GND), and the WiFi serial communications signals (COM_TEST header).

PMC-Eight™ Controller Version 2A-06B Test Points

The PMC-Eight™ model 2A-06B WiFi module (Microchip RN-131G) daughter board has a test point (TP_IO9) used in resetting the module to the Microchip factory defaults. Explore Scientific PMC-Eight™

Application Note PMC8-AN002: Connecting to the PMC-Eight™ with a Terminal Program to Configure the RN-131 WiFi Interface and Switching Between the WiFi Interface and the Serial Interface (available

in the Appendix at the end of this document) describes in detail how to connect to the Microchip RN-131 Module and restore the PMC-Eight™ default configuration.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

PMC-Eight™ Controller WiFi Daughter Board

CAUTION: Changing the WIFI module configuration from the default factory configuration is at

your own risk.

You can also use Application Note AN002 to configure the Microchip RN-131 Module to communicate on your Local Area Network (LAN). The Microchip RN-131 WiFly Command Reference Manual is located at

http://ww1.microchip.com/downloads/en/DeviceDoc/50002230B.pdf.

WiFi Channel Selection

In some instances, the WiFi environment is very busy with several SSIDs, and if the PMC-Eight™ WiFi module is configured to use the same channel as others, this can disrupt the communications, regardless of the signal strength, and may make the PMC-Eight™ WiFi drop out. The default channel configured in the RN-131 wireless module is channel 6, which is a popular channel for many WiFi devices. The solution is to change the WiFi channel. You can do this with the ST4 port (RJ12) dongle included with your PMCEight™ system. You can learn more about how WiFi and channels work in the specification document for IEEE 802.11. An overview is available here: https://en.wikipedia.org/wiki/IEEE_802.11

Here is the procedure to increment the channel number:

NOTE: You can monitor the channel number selected by the channel change procedure by downloading, installing, and running the program WiFiInfoView available at:

http://www.nirsoft.net/utils/wifi_information_view.html

1. Power up the PMC-Eight™ and it will boot up (the lights will settle out).

2. Insert the dongle into the Autoguider port (ST4 RJ12).

3. Watch the LEDs cycle, as the system reboots.

4. Remove the dongle.

5. Wait until the LEDs settle down, then Reconnect your tablet to the mount’s SSID.

6. Try to connect the ExploreStars or ASCOM Client application to the PMC-Eight™

7. IF you still cannot connect and see the “Please Wait” message, THEN press the reset button.

8. Repeat steps 2 – 7 as needed.

It is recommended to power down the system and then power it back up between steps 3 and 4, but this shouldn't be necessary. If the new channel still gives problems, the procedure can be repeated (step 8) until successful. The number (channel) will increment by one each time the dongle is used to change the channel and will recycle back to 1 after reaching channel 11. There are 11 channels available in total, channels 1–11.

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

III PMC-Eight™ Controller and Command Language Theory of Operation

Controller Theory of Operation

The PMC-Eight™ Precision Motion Controller is designed to enable the quick and reliable movement of the telescope OTA to point to any object of interest on the celestial sphere. The controller is made up of three main electronic subsystems: a) Computer Processor and Memory System, b) Motor Driver System, and c) Communications Interface.

The Computer Processor and Memory System processes and interprets the incoming commands and provides data output to the communications channels. Eight processors are integrated into the microcontroller chip (Parallax Propeller Microprocessor P8X32A), each with its own dedicated memory space and common memory space for sharing information between the processors. There is also a system RESET/REBOOT momentary push-button switch next to the 12 Vdc Power input. Two processors are dedicated to communicating with each motor, reading the real-time motor parameters, and generating the required DIRECTION and RATE motion values real-time to command the motors . One processor is dedicated to communicating via the RS232 Serial Port via the port driver. One processor is dedicated to taking the commands and translating them into executable instructions. One processor is dedicated to monitoring the motor status and reading the Autoguider port. Two processors for the motors are used only when monitoring the status of the real-time SLEW process. The processors run independently so that if any one processor fails, it will not affect the operation of the others.

PMC-Eight™ System Architecture

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The Texas Instrument DRV8834 Motor Driver integrated circuit chip (one for each motor channel) is designed to generate the required low-level stepper motor control/drive signals at the proper voltage and current levels needed to drive the mount as required. A performance margin is built into the system to enable the mount to operate over a wide temperature range. These motor driver chips are low power and very efficient in delivering the power to the stepper motors reliably.

PMC-Eight™ Communications

There are three communication interfaces on the system. The first is the base serial interface using the RS232 hardware specification and the Parallax recommended interface circuitry to provide basic communications to transfer firmware and data to the permanent memory of the Computer Processor and to configure the wireless network Wi-Fi processing module.

PGMR/ ST4

Serial Autoguider DEC RA RST PWR LEDS

Model 2A PMC-Eight™ connections.

The model 2A-06B serial command processor/interpreter can be accessed via the RS232 port and via the second interface, the RN-131 wireless network interface. The model 1A-01C serial command processor/interpreter can be accessed via the mini-USB Type B port and via the second interface, the ESPWROOM-02 (ESP8266) wireless network interface. The third communications channel is via the RJ 6P6C connector configured as an SBIG ST4 Autoguider Port. This port is also used to change the WiFi Channel, when needed, using the supplied ST4 port dongle.

PMC-Eight™ Fixed Tracking Rates

There are several fixed tracking rates available for the PMC-Eight™ ASCOM driver and one fixed rate is

available for selection in the ExploreStars™ application. The Sidereal, Solar, Lunar, and Average King rates

are available for selection. The following tables show the tracking rate values and their corresponding settings in the customer rate section of the ExploreStars application. These rates are pre-defined in the ASCOM driver.

NOTE: The different mount rates specified in microstep sec-1 are specified to the nearest 0.04 (± 0.02)”arc sec-1. This value is based on the internal precision of the firmware integer calculation and setting of the precision tracking rate value. (See

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Application

Object Rate

Solar-Second Rate Value

“arc sec-1

Sidereal-Second Rate Value

“arc sec-1

ExploreStars

Sidereal

15.041

15.000

ASCOM Driver

Sidereal

15.041

15.000

ASCOM Driver

Solar

15.000

14.959

ASCOM Driver

Lunar

14.491

14.451

ASCOM Driver

Average King

15.037

14.996

Fixed Tracking Rate Values

Fixed Tracking Rate

G11 microstep sec-1

@0.28125 arc-sec microstep-1

EXOS 2 & iEXOS 100 microstep sec-1

@0.31250 arc-sec microstep-1

Sidereal

53.32

48.00

Solar

53.20

47.88

Lunar

51.40

46.24

Average King



53.32

48.00

Custom Rate

See Calculation

See calculation

Explore Stars Mount Rate Setting Values



The value of 53.32 microstep sec-1 in the table for the G11 is very close to the actual calculated Average

King rate of 53.3191 microstep sec-1.

The user can also set a custom rate value based on the following equation:

Microstep Rate Value (microstep sec-1) = Sidereal-Second Rate Value (“arc sec-1) / X (“arc microstep-1) Where X = specific mount’s motor scaling value in “arc microstep-1

For example, if you want to visually observe a comet with the ExploreStars application that is moving across the sky in RA a little faster than Sidereal, namely at 16.35 “arc sidereal-sec-1 with your G11 mount, then the calculation would be:

Rate Value = (16.35 “arc sidereal-sec-1/ 0.28125 ”arc microstep-1) = 58.133 microstep sec-1 = 58.12 microstep sec-1 (rounded to nearest ±0.02 microstep sec-1)

When this value is entered the ExploreStars application would immediately start tracking at that rate. There would still be a need to move the mount in Declination due to the objects motion in the Declination axis that is not corrected when in the “square-T” Tracking Mode.

Autoguider (ST4) Port

Both the model 2A and model 1A ST4 port have dedicated interface circuitry to provide contact input commands into the controller to slowly move the mount in the four cardinal directions to correct for any tracking errors due to drift in Right Ascension (RA) or Declination (DEC) drift caused by less than perfect polar alignment.

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The ST4 port on the PMC-Eight™ model 2A-06B uses an analog multiplexer design (VCO) to convert the four contact inputs sent from the Autoguider camera to the controller into numeric values that can be processed by the firmware into direction values (N, S, E, W). The analog design requires a factory default calibration that is included in the firmware. The port meets all the SBIG ST4 standard requirements for processing a “contact closure” input. Contacts are between each direction pin (N, S, E, W) and the common pin.

Most guide cameras provide an ST4 compliant “contact closure,” or equivalent, via a MOSFET transistor circuit using a high-quality component. Some cameras, however, do not have a MOSFET transistor that provides the correct “contact closure” input resistance (shorted input) but instead provides a higher resistance input that does not work with the PMC-Eight™ ST4 factory default calibration. In this case, customers must contact Explore Scientific to have their ST4 input calibrated to their specific camera. See Appendix VIII.4 “Explore Scientific PMC-Eight™ version 2A-006A/B Autoguider (ST-4) Port Calibration Procedure (Rev 1.3) Firmware Version 9r4 08162015 AND LATER (2015 August 22)” for details on this procedure.

The ST4 port on the PMC-Eight™ model 1A-01C uses a digital transistor optocoupler circuit design that provides a reliable and optically isolated input to the controller from the guide camera system. This updated digital transistor optocoupler circuit design has also been incorporated into the latest Model 2A07A board design. The significance of this design is that it does not require calibration.

Autoguiding (ST4) Port Pinout

Inputs to the Autoguider port are interpreted by the firmware to adjust the rate according to the Sidereal Rate Fraction, i.e., Percent Sidereal Rate, configured in the PMC-Eight™ ASCOM driver. The factory default value is set to 40% or 0.4 x 15.00”arc sec-1, or 6.00”arc sec-1. This value is stored in the system EEPROM as Parameter 3 (P3) so that when using the ST4 port and RJ12 (6P6C) cable to connect directly to an Autoguider camera, that camera knows what value to use. The Autoguiding software, PHD2™ corrects any tracking error by sending pulses to the mount that are different time intervals typically from 20 mS to 200+ mS in length, depending on the amount needed to move the mount back to the target star that PHD2™ is locked onto.

The total movement needed to correct a position error is the product of correction rate and pulse time. For example, with a measured position error of 1.07”arc and the Sidereal Rate Fraction set to 0.40 or

6.00”arc second-1, the pulse time would equal the position error 1.07”arc / 6.00”arc second-1, or 0.178 seconds (178 mS).

Explore Scientific PMC-Eight™ Controller Programmer’s Reference DOC-ESPMC8-002 Rev. 1.2 2019 March 07 (Firmware 09T10, 10A01 and above)

Command Language Theory of Operation

The Explore Scientific Command Language commands are used to send data requests and instructions to control the motors and receive status data back from the hardware. Four basic types of commands are used to interrogate the controller, two general purpose commands, and two special purpose commands. The GET and SET commands are used to get and set real-time motor parameters. These are general purpose commands to get and set a variety of parameters. The two special purpose commands are the POINT and TRACK commands. Each of these commands are applied to a given motor axis defined by the AXIS value. With a telescope mount there are 2 predefined axes: AXIS 0: RA/AZ, AXIS 1: DEC/ALT. This command language can support multiple axis controllers with any number of axes.

The GET and SET commands have several primary parameters dealing with motor operation: DIRECTION, POSITION, RATE, and TARGET. The three main parameters, DIRECTION, POSITION, and RATE are statically set and are fixed until the next time they are changed with a SET command. The SET commands for DIRECTION and RATE are immediate commands and update the values in real time. The SET POSITION command is used to adjust the motor position coordinates when calibrating the position in reference to the celestial coordinate system, or when SYNCING with the celestial coordinates of a given object.

The GET commands allow you to interrogate the controller for various real-time parameters, including: DIRECTION, POSITION, RATE, and TARGET. Other parameters that are available are FIRMWARE VERSION, SYSTEM INFORMATION via an Index value, and the current TRACKING RATE value.

NOTE: The SYSTEM INFORMATION command is not implemented in firmware versions 9T10, 11, and 12, and 10A01.

The controller is designed to handle the requirement for fast slews and very slow, precise tracking rates by implementing two rate types, like a HIGH and LOW in a four-wheel drive vehicle. Standard Rate (SLEW) and Precision Track Rate (TRACK) commands are provided. The SLEW Rates are 25x faster than the TRACK Rates. The rate values can be set to any value between 0 and 40000 (decimal), 0x9C40 (hexadecimal). For the ES/Losmandy G-11, this equates to SLEW rates up to 3.125 sec-1 on each axis1. This allows the system to SLEW the telescope 180 across the sky in 60 seconds. The TRACK rate allows for setting the RA motor rate up to 450.00”arc sec-1 with an accuracy of ±0.006”arc sec-1. The standard GET/SET RATE command sets the SLEW rates. The TRACK command and GET TRACKING RATE command are used to SET/GET a more precise tracking rate value. This is an equivalent rate selection range of 1:1000000.

The POINT command is a higher-level FIRMWARE command that automatically calculates the necessary rates to efficiently SLEW to a TARGET. The process algorithm handles the ramping up and down of the motor rate to manage the inertial load placed on the stepper motors. In addition, the motor current is carefully managed to provide enough torque while slewing to accurately position the telescope on the object desired without exceeding the motor capability. The GET/SET commands for FIRMWARE VERSION and SYSTEM INFORMATION are used to query and set various values such as communications BAUD rate, Sync Offset Positions, and Axis Scale values.

This angular rate is for the ES/Losmandy G-11 mount. Other mounts will slew faster or slower, depending on the

total motor counts for the drive.

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Explore Scientific PMC-Eight ESOGT-01B Programmer's Reference Manual

Specifications and Main Features

Frequently Asked Questions

User Manual