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© 2017 Jackson Labs Technologies, Inc.

35

Mini-JLT GNSS™

 User Manual

3.10.11 SERVo:1PPSoffset

This command sets the Mini-JLT GNSS™ 1PPS signal’s offset to UTC in 16.7ns steps.
Using the SERV:1PPS command results in immediate phase change of the 1PPS output signal.
This command has the following format:

SERVo:1PPSoffset        <int> ns

3.10.12 SERVo:TRACe

This command sets the period in seconds for the debug trace. Debug trace data can be used with 
Ulrich Bangert’s “Plotter” utility to show UTC tracking versus time etc.
This command has the following format:

SERVo:TRACe   <int >  [0,255]

An example output is described here:

08-07-31 373815 60685 -32.08 -2.22E-11 14 10 6 0x54

[date][1PPS Count][Fine DAC][UTC offset ns][Frequency Error Estimate][Sats Visible][Sats 
Tracked][Lock State][Health Status]
Please see the 

SYNChronization?

 command for detailed information on how to decode the health 

status indicator values. The Lock State variable indicates one of the following states:

3.10.13 SERVo?

This command returns the result of the following queries:

SERVo:COARSeDac?
SERVo:DACGain?
SERVo: EFCScale?
SERVo:EFCDamping?

Value

State

0

OCXO warmup

1

Holdover

2

Locking (OCXO training)

4

[Value not defined]

5

Holdover, but still phase locked (stays in this 
state for about 100s after GNSS lock is lost)

6

Locked, and GNSS active

Summary of Contents for Mini-JLT GNSS

Page 1: ...Mini JLT GNSS User Manual Document 80200549 Version 1 1 Date 28 August 2017 ...

Page 2: ...Mini JLT GNSS User Manual Copyright 2017 Jackson Labs Technologies Inc ...

Page 3: ...ions 11 3 1 Introduction 11 3 2 General SCPI Commands 11 3 2 1 Quick Start Commands 11 3 2 2 IDN 11 3 2 3 HELP 12 3 3 GPS Subsystem 12 3 3 1 GPS SATellite 13 3 3 2 GPS SATellite TRAcking COUNt 13 3 3 3 GPS SATellite VISible COUNt 13 3 3 4 NMEA Support 13 3 3 5 GPS GPGGA 14 3 3 6 GPS GGASTat 14 3 3 7 GPS GPRMC 14 3 3 8 GPS GPGSV 14 3 3 9 GPS XYZSPeed 15 3 3 10GPS GPZDA 15 3 3 11GPS PASHR 15 3 3 12G...

Page 4: ... 26 3 5 8 PTIMe LEAPsecond DATE 26 3 5 9 PTIMe LEAPsecond DURation 26 3 5 10PTIME 26 3 6 SYNChronization Subsystem 27 3 6 1 SYNChronization HOLDover DURation 27 3 6 2 SYNChronization HOLDover INITiate 27 3 6 3 SYNChronization HOLDover RECovery INITiate 28 3 6 4 SYNChronization SOURce MODE 28 3 6 5 SYNChronization SOURce STATE 28 3 6 6 SYNChronization TINTerval 28 3 6 7 SYNChronization TINTerval TH...

Page 5: ...Flash Loader Utility installation 37 4 2 1 Philips LPC2000 Flash Utility 37 4 2 2 Flash Magic Flash Programming Utility 38 4 3 Putting the PCB into In Circuit Programming ISP mode 38 4 4 Downloading the firmware 38 4 4 1 Philips LPC2000 Flash Utility 38 4 4 2 Flash Magic Flash Programming Utility 40 4 5 Verifying Firmware Update 43 5 GPSCon Utility 45 5 1 Description 45 5 2 Installation 45 5 3 Usi...

Page 6: ...Mini JLT GNSS User Manual 4 2017 Jackson Labs Technologies Inc ...

Page 7: ...roved thermal stability Allan Deviation and Phase Noise performance The unit also adds support for NMEA and SCPI communication commands and removes support for TSIP proprietary commands The Mini JLT GNSS GPSDO uses a multi GNSS receiver that can run in stationary Position Hold mode and mobile mode to discipline an OCXO local oscillator to better than 1ppb frequency accuracy It supplies two 10MHz o...

Page 8: ...amage injury and or death in case of a lightning strike 1 2 2 Grounding To avoid damaging the sensitive electronic components in the Mini JLT GNSS GSPDO always make sure to discharge any built up electrostatic charge to a good ground source such as power supply ground This should be done before handling the circuit board or anything connected to it i e the GNSS antenna 1 2 3 Power Connections Make...

Page 9: ... better than 1ppb frequency accuracy By default the unit will be set to Position Hold mode and an antenna position Auto Survey process is started after power on that may take up to 3 hours to finish The antenna should never be moved when the unit is set to run in Position Hold mode as this would result in loss of frequency and timing accuracy and incorrect GNSS fixes The unit must be configured to...

Page 10: ... on connector J1 as the default configuration is TTL level Both the TTL serial port J1 and the USB port are internally ored together so the user may send and receive commands to from both ports as long as commands are not sent to both ports at the same time Try some of these SCPI commands help syst stat GPS sync meas 2 1 1 PCB Photos The Mini JLT GNSS PCB is shown in Figure 2 1 Figure 2 1 Mini JLT...

Page 11: ...gnal J1 Pin 3 Serial RX Serial Receive Input 3 3V LVCMOS RS 232 serial optional 5V compatible Serial Receive input for SCPI commands internally wired ored to USB RX signal J1 Pin 4 Ground Ground Ground Main Power Return J1 Pin 5 VANT External Antenna Voltage 3 0V to 5 5V up to 100mA The unit provides a 3 3V antenna supply to the GNSS antenna by default This can be over driven by a voltage 3 3V sup...

Page 12: ...ogramming mode ISP when pulled low during power on typically enabled by using a jumper to pin 1 3 3V GPS is receiving a sat fix 0V GPS is not receiving a sat fix Not stuffed by default for legacy compatibility J5 Pin 1 Ground Ground Ground Ground Not stuffed by default for legacy compatibility J4 GNSS Antenna Antenna Input L1 3 3V default to 5 5V Supplies 3 3V by default and up to 5 5V when using ...

Page 13: ... up to 72 GNSS satellites in challenged reception areas such as in urban canyons under foliage indoors or close to the earth s poles etc Using multiple GNSS systems also increases robustness by not relying on a single GNSS system Several of the systems operate at different carrier frequencies so using multiple can increase immunity against jamming which often occurs at only one frequency The multi...

Page 14: ...le environment where the antenna position can change more than 1 foot during operation The Mini JLT GNSS is capable of generating standard navigation messages see GPS GPGGA GPS GPZDA GPS PASHR and GPS GPRMC TTL serial commands that are compatible with most GPS based navigation software The GNSS receiver generates a 1PPS time signal that is phase synchronized to UTC This 1PPS signal is used to freq...

Page 15: ...ble oven OCXO and 6 0 simple single oven OCXO are typical EFC Damping overall IIR filter time constant higher values increase loop time constant Jackson Labs Technologies Inc typically uses values between 10 to 50 Setting this value too high may cause loop instability Phase compensation this is the Integral part of the PID loop This corrects phase offsets between the Mini JLT GNSS 1PPS signal and ...

Page 16: ...Mini JLT User Manual 10 2017 Jackson Labs Technologies Inc Figure 2 3 Mini JLT GNSS phase compensation plot ...

Page 17: ...o Symmetricom 58503A commands To get a listing of the available commands send the HELP query This will return a list of all the available commands for the Mini JLT GNSS GPSDO Additional information regarding the SCPI protocol syntax can be found on the following web site http www ivifoundation org scpi A basic familiarity with the SCPI protocol is recommended when reading this chapter 3 2 General ...

Page 18: ...coordinate system The GPS subsystem regroups all the commands related to the control and status of the GNSS receiver The list of the commands supported is the following GPS SATellite TRAcking COUNt GPS SATellite VISible COUNt GPS GPGGA int 0 255 GPS GGASTat int 0 255 GPS GPRMC int 0 255 GPS GPGSV int 0 255 GPS GPZDA int 0 255 GPS PASHR int 0 255 GPS XYZSPeed GPS GYRO GPS GYRO CAL GPS DYNAMic int 0...

Page 19: ...d out information on the TTL and USB serial transmit pin automatically every N seconds All incoming serial commands are still recognized by Mini JLT GNSS since the serial interface transmit and receive lines are completely independent of one another For compatibility with existing GPS only products the Mini JLT GNSS GPSDO s NMEA output only uses the GPS NMEA sentence headers GPGGA GPGSV etc regard...

Page 20: ...detailed description of the lock state variable The command allows capture of the position and other information available in the GGA command as well as tracking the lock state and health of the unit s OCXO performance GGASTat shows height in MSL Meters this is different from traditional GPS receivers that display height in GPS Meters The difference between MSL and GPS height can be significant 35...

Page 21: ...message which allows proper calculation of GPS time from UTC time as indicated by other messages as well as proper handling of Leapsecond events Use the following format to generate the velocity vector every N seconds with N in the interval 0 255 GPS XYZSPeed int 0 255 3 3 10 GPS GPZDA This command instructs the Mini JLT to send the NMEA standard string GPZDA every N seconds with N in the interval...

Page 22: ...g gg Antenna Height in meters hhhh Four fixed symbols iii ii Course Over Ground jjj jj Speed in Knots kkkk k Vertical Velocity in meters s ll l PDOP mm mHDOP nn nVDOP 00 0Static number p pp Firmware Version 1 05 and above This command instructs the Mini JLT GNSS to send the NMEA standard string PASHR every N seconds with N in the interval 0 255 The command is disabled until the GNSS receiver achie...

Page 23: ... Degrees when acceleration greater than 1g is applied 3 3 13 GPS GYRO CAL This command calibrates the output period of the Accelerometer data in g s per axis and in tilt in Degrees per axis Both offset and gain need to be calibrated on the unit to properly format the output of the three axis tilt to be 90 Degrees to 90 Degrees and the 0 Degree reference By default the unit is shipped with a normal...

Page 24: ...en the unit is sitting level horizontally 3 3 14 GPS DYNAMic MODE This command allows the user to select the dynamic motion model being applied to the Kalmann filters in the GNSS receiver This allows for larger amounts of filtering for lower velocity applications effectively reducing noise and multipath interference Applications with high acceleration can now be used with fast filter settings to a...

Page 25: ...n for GPS DYNAMIC MODE The current dynamic state being applied to the GNSS receiver can be queried with the command GPS DYNAMIC STATE Please note that this command syntax has changed from previous products such as the FireFly IIA GPSDO units which did not support Position Hold Auto Survey modes 3 3 15 GPS DYNAMic MODE 8 Automatic Dynamic Mode Automatic Dynamic Mode allows the Mini JLT GNSS GPSDO f...

Page 26: ...motive mode The following command returns the setting of the GNSS dynamic model GPS DYNAMic MODE The actual state chosen by the firmware for the GNSS receiver based on vehicle velocity can be obtained with the command GPS DYNAMic STATe A value between 0 and 7 is then returned depending on vehicle dynamics The dynamic state is always set to STATIONARY if one of the Position Hold Auto Survey station...

Page 27: ... with 1 5ns per foot propagation delay would be compensated with the following command GPS REF ADEL 45ns This command can be used to fine tune different units to have co incident 1PPS pulse outputs Please note that during normal operation the 1PPS pulse may wander around the UTC 1PPS pulse while the unit is tracking the GNSS signals The present offset between the 1PPS output and the UTC 1PPS signa...

Page 28: ...3 3 21 GPS SURVey ONCE This command starts a Survey At the end of the Survey the calculated Hold position will be stored in NVRAM The Survey parameters can be set with the command GPS SURVey DURation and GPS SURVey VARiance 3 3 22 GPS SURVey DURation sec This command sets the Survey minimal duration 3 3 23 GPS SURVey VARIANCE mm2 This command specifies the minimum variance of the average position ...

Page 29: ...are available This command allows setting the internal RTC TIME manually when operating the unit in GPS denied environments This command is compatible to the PTIME OUT ON command described in section 3 5 5 to allow automatic time and date synchronization of two units to each other The internal RTC is driven by the highly stable ovenized oscillator 10MHz signal and thus has very high accuracy 3 3 2...

Page 30: ...eiver in one convenient location 3 4 GYRO SUBSYSTEM The following Gyro commands are supported on the Mini JLT GNSS unit GYRO MODE ON OFF GYRO TRACE int 0 255 GYRO CALibrate float float float float float float GYRO CALibrate COMPute GYRO CALibrate RESET GYRO SENSitivity float float float GYRO EFC float GYRO GLOAD 3 4 1 GYRO MODE ON OFF Enables or disables electronic compensation This feature must b...

Page 31: ...nd 0g indication based on entering these values The GYRO CAL COMPUTE command will query the user for the maximum and minimum indicated g loads The GYRO TRACE 10 command can be used to help establish the g indications on the three different axis to aid in this calibration 3 4 5 GYRO SENS GYRO EFC and GPS CAL RESET Used for factory calibration of Gyro subsystem 3 4 6 GYRO GLOAD This command will ret...

Page 32: ...c data is not available The GNSS receiver must have the GPS system enabled for the GPS Almanac to be available 3 5 7 PTIMe LEAPsecond ACCumulated This command returns the internally applied leapsecond offset between GPS time and UTC time as stored in the EEPROM GPS Almanac not received yet or as indicated by the GNSS receiver GPS Almanac is available 3 5 8 PTIMe LEAPsecond DATE This command return...

Page 33: ...first number in the response is the holdover duration The duration units are seconds and the resolution is 1 second If the Receiver is in holdover the response quantifies the current holdover duration If the Receiver is not in holdover the response quantifies the previous holdover The second number in the response identifies the holdover state A value of 0 indicates the Receiver is not in holdover...

Page 34: ...will initiate a counter reset jam sync aligning the oscillator generated 1PPS with the reference 1PPS phase The oscillator phase is slowly and continuously adjusted toward 0ns offset to the reference 1PPS while the phase difference is less than the THReshold phase limit The oscillator generated 1PPS phase is allowed to drift up to this threshold before a jam sync is initiated The default setting i...

Page 35: ...bit of the binary equivalent of the hexadecimal health status flag The following system parameters are monitored and indicated through the health status indicator Individual parameters are ored together which results in a single hexadecimal value encoding the following system status information As an example if the unit is in GNSS receiver holdover and the OCXO voltage is too high and the UTC phas...

Page 36: ...AGnostic ROSCillator EFControl RELative DIAGnostic ROSCillator EFControl ABSolute DIAGnostic LIFetime COUNt 3 7 1 DIAGnostic ROSCillator EFControl RELative This query returns the Electronic Frequency Control EFC output value of the internal reference oscillator It returns a percentage value between 100 to 100 3 7 2 DIAGnostic ROSCillator EFControl ABSolute This query returns the Electronic Frequen...

Page 37: ...JLT The list of the commands supported for this subsystem follows SYSTem COMMunicate SERial ECHO ON OFF SYSTem COMMunicate SERial PROmpt ON OFF SYSTem COMMunicate SERial BAUD 9600 19200 38400 57600 115200 SYSTem STATus SYSTem FACToryReset ONCE 3 9 1 SYSTem COMMunicate 3 9 1 1 SYSTem COMMunicate SERial ECHO This command enables disables echo on TTL serial This command has the following format SYSTe...

Page 38: ...are overwritten with factory default values 3 10 SERVO Subsystem This subsystem regroups all the commands related to the adjustment of the servo loop SERVo COARSeDac int 0 225 SERVo DACGain int 0 1 10000 SERVo EFCScale float 0 0 500 0 SERVo EFCDamping float 0 0 4000 0 SERVo SLOPe NEG POS SERVo TEMPCOmpensation float 4000 0 4000 0 SERVo AGINGcompensation float 10 0 10 0 SERVo PHASECOrrection float ...

Page 39: ... increased gain value difference will be reduced every second by 1 3600 so that the gain after two seconds would be 1 3998 until after 3600 seconds the gain has been reduced back to its long term value of 0 70 as stored in the SERVo EFCscale parameter Disabling the FASTLOCK mode is accomplished by setting the SERVo FASTlock to 1 This will set the dynamic gain to 1 0 effectively disabling the fastl...

Page 40: ...o SLOPe The parameter determines the sign of the slope between the EFC and the frequency variation of the OCXO This parameter should be set to match your OCXO s EFC frequency slope This command has the following format SERVo SLOPe NEG POS 3 10 8 SERVo TEMPCOmpensation This command is not supported on the Mini JLT board 3 10 9 SERVo AGINGcompensation This parameter is a coefficient that represents ...

Page 41: ...ormat SERVo TRACe int 0 255 An example output is described here 08 07 31 373815 60685 32 08 2 22E 11 14 10 6 0x54 date 1PPS Count Fine DAC UTC offset ns Frequency Error Estimate Sats Visible Sats Tracked Lock State Health Status Please see the SYNChronization command for detailed information on how to decode the health status indicator values The Lock State variable indicates one of the following ...

Page 42: ...Mini JLT GNSS User Manual 36 2017 Jackson Labs Technologies Inc SERVo SLOPe SERVo TEMPCOmpensation SERVo AGINGcompensation SERVo PHASECOrrection SERVo 1PPSoffset SERVo TRACe ...

Page 43: ...abs Technologies Inc website under the Support tab http www jackson labs com index php support The Flash Magic utility is available for download on the Flash Magic website http www flashmagictool com 4 2 1 Philips LPC2000 Flash Utility The first is the Philips LPC2000 utility version 2 2 3 Please note that some computers are known to be incompatible with the LPC2000 flash utility Preliminary inves...

Page 44: ...hat will be remembered The file is in hex format The unit needs to be connected to the computer s TTL serial port prior to firmware download The Mini JLT GNSS is TTL level compatible A TTL to RS 232 converter must be used when connecting to the computer s RS 232 serial port to prevent damage to the board Connect a USB or TTL serial connector to the Mini JLT GNSS as indicated in Section 2 1 1 The u...

Page 45: ...or less it will not work faster than 38400 Baud The DEVICE should show up as LPC2138 after pressing READ DEVICE ID Also please point the Filename to the directory where you have stored the latest firmware hex file that is to be downloaded D Start the download by pressing Upload to Flash button The following window should appear if the correct COM port has been chosen etc ...

Page 46: ...o be tried several times It is not necessary to press reset as the utility is asking Just press OK on the utility window s button Warning DO NOT PRESS THE ERASE BUTTON AT ANY TIME THIS WILL RENDER THE PCB USELESS AND CAN ONLY BE RECOVERED AT THE FACTORY 4 4 2 Flash Magic Flash Programming Utility A Open the Flash Magic utility Set the COM port in the Flash Magic application as needed on your PC Se...

Page 47: ... 2017 Jackson Labs Technologies Inc 41 Mini JLT GNSS User Manual Figure 4 3 Flash Magic utility B Press the Select Device button and the window shown in Figure 4 4 will appear ...

Page 48: ...Mini JLT GNSS User Manual 42 2017 Jackson Labs Technologies Inc Figure 4 4 Device selection window C Expand the ARM7 folder and select the appropriate processor in this case the LPC2138 ...

Page 49: ... unit will not operate and will have to be returned to the factory Checking this box on the ISP utility will thus void the warranty G Under Step 3 Hex File browse for the hex file that you downloaded in step 4 4 H Go to Step 5 and press Start You will observe the firmware being downloaded to the Mini JLT GNSS 4 5 Verifying Firmware Update Power cycle the unit with the pin 2 of J5 ISP left floating...

Page 50: ...Mini JLT GNSS User Manual 44 2017 Jackson Labs Technologies Inc ...

Page 51: ...om index php support 5 2 Installation Extract the contents of the ZIP file downloaded from the Jackson Lab s website and execute the MSI installer Follow the on screen instructions to complete the installation of GPSCon 5 3 Using GPSCon The GPSCon utility has a help file that should be consulted in order to get the full functionality of this utility Only a few of the features and commands are ment...

Page 52: ... Stop Bits to 1 Set Flow Control to None Once you have configured the communication parameters press the OK button to close the window 5 3 1 2 Auxiliary Parameters After pressing the wrench icon you can select the Auxiliary tab to configure auxiliary measurements See Figure 5 3 for an example of an auxiliary measurement You will notice that the Aux1 request string has been set to meas current CR a...

Page 53: ...nt The labels and parameters are completed by default for traces 1 thorugh 5 The auxiliary trace defined on the auxiliary tab for trace 6 has the label Temp to indicate that the OCXO current from the meas current query is a measure of temperature Any of the eight traces can be replaced by auxiliary traces as described in Section 5 3 1 2 Press the Help button for a full description of each option i...

Page 54: ...Mini JLT GNSS User Manual 48 2017 Jackson Labs Technologies Inc Figure 5 3 Auxiliary Parameters window Figure 5 4 Traces Parameters window ...

Page 55: ...ver over the buttons to see the exact command that is sent Figure 5 5 Sending manual commands 5 3 3 Using the Mouse in the Graph Window Refer to Figure 5 6 for the following description The default view in GPSCon is All which you can select with the View All menu option To see a larger view of the graph select the View Graph menu option In the graph window the horizontal range of the graph can be ...

Page 56: ...nt becomes the left end of the curve Then similarly click the right mouse button on the curve at the time you wish to be the right most portion of the magnified curve and it immediately becomes the end point on the right side And finally to return to the zoomed out fit to window view left double click on the curve When you have locked the start and stop time using the mouse you can scroll left or ...

Page 57: ...the entire logfile contents Use the checkbox Export all graph data to make this choice You may select a size of the exported images in X and Y The file format may be BMP JPG GIF or PNG Your settings will be stored and will be the default next time you open this dialog If you choose to export the graph you might want to override the TI max setting in force on the screen display You may do this by e...

Page 58: ...unit over a period of more than 200 hours The red trace is EFC crystal frequency control voltage The crystal is aging becoming faster in frequency over time This requires the control voltage to be lowered to maintain precisely 10 0MHz A drift of 2mV is visible over 200 hours On the left side of the screen the EFC range over this 200 hour plot is displayed vertically as 0 00193V This means the drif...

Page 59: ...the OCXO in the evenings heating it up and thus making the unit use lower power during that event In Figure 5 9 which is a zoom of Figure 5 8 we can see the phase offset error of the internal OCXO to the UTC GPS reference We can see the maximum drift is 77ns to 93ns The average is TI av 0 03ns The standard deviation over the 200 hour plot is sd 11ns This means the average error of the 10MHz phase ...

Page 60: ...Mini JLT GNSS User Manual 54 2017 Jackson Labs Technologies Inc ...

Page 61: ...ustomer shall prepay shipping charges and shall pay all duties and taxes for products returned to Jackson Labs Technologies Inc for warranty service Except for products returned to Customer from another country Jackson Labs Technologies Inc shall pay for return of products to Customer If Jackson Labs Technologies Inc is unable within a reasonable time to repair or replace any product to condition ...

Page 62: ...ackson Labs Technologies Inc products are not intended for use in medical life saving or life sustaining applications 6 1 3 Exclusive Remedies THE REMEDIES PROVIDED HEREIN ARE THE CUSTOMER S SOLE AND EXCLUSIVE REMEDIES JACKSON LABS TECHNOLOGIES INC SHALL NOT BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES WHETHER BASED ON CONTRACT TORT OR ANY OTHER LEGAL THEORY ...

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