Jackson labs Micro-jlt gnss User manual

Micro-JLT GNSS™

User Manual

Document: 80200550

Version: 1.2

Date: November 6, 2019

Micro-JLT GNSS™ User Manual

1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 General Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 Antenna Lightning Protector . . . . . . . . . . . . . . . . . . . . . 2

1.2.2 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.3 Power Connections. . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.4 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . 3

2 Quick-Start Instructions . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Powering Up the Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.1 PCB Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1.2 Mechanical Drawings . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.3 Notes on Signal Interfacing and J1 Connector . . . . . . . . . . . . . . 9

2.1.4 Coaxial Connectors. . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

2.3 Concurrent-GNSS Capabilities . . . . . . . . . . . . . . . . . . . . . . .10

2.4 Connecting the GNSS Antenna . . . . . . . . . . . . . . . . . . . . . . 11

2.5 Remote serial control . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.6 Loop parameter adjustment . . . . . . . . . . . . . . . . . . . . . . . . 11

3 SCPI-Control Quick Start Instructions . . . . . . . . . . . . . . 13

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 General SCPI Commands . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2.1 Quick Start Commands . . . . . . . . . . . . . . . . . . . . . . . 13

3.2.2 *IDN? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.2.3 HELP?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

3.3 GPS Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

3.3.1 GPS:SATellite . . . . . . . . . . . . . . . . . . . . . . . . . . .15

3.3.2 GPS:SATellite:TRAcking:COUNt? . . . . . . . . . . . . . . . . . . .15

3.3.3 GPS:SATellite:VISible:COUNt? . . . . . . . . . . . . . . . . . . . . 15

3.3.4 NMEA Support . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.3.5 GPS:GPGGA <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 16

3.3.6 GPS:GGASTat <int> [0,255] . . . . . . . . . . . . . . . . . . . . . 17

3.3.7 GPS:GPGLL <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 17

3.3.8 GPS:GPRMC <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 17

3.3.9 GPS:GPGSA <int> [0,255] . . . . . . . . . . . . . . . . . . . . . .18

3.3.10GPS:GPGSV <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 18

3.3.11GPS:XYZSPeed <int> [0,255] . . . . . . . . . . . . . . . . . . . .18

3.3.12GPS:GPVTG <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 19

3.3.13GPS:GPZDA <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 19

3.3.14GPS:PASHR <int> [0,255] . . . . . . . . . . . . . . . . . . . . . .20

3.3.15GPS:PJLTS <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 21

3.3.16GPS:PJLTV <int> [0,255] . . . . . . . . . . . . . . . . . . . . . . 21

3.3.17GPS:GYRO . . . . . . . . . . . . . . . . . . . . . . . . . . .22

3.3.18GPS:GYRO:CAL . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3.19GPS:DYNAMic:MODE <int> [0,7] . . . . . . . . . . . . . . . . . . . 22

3.3.20GPS:DYNAMic:MODE 8 (Automatic Dynamic Mode) . . . . . . . . . . . 23

3.3.21GPS:DYNAMic:STATe? . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.22GPS:REFerence:ADELay <float> <s | ns > [-32767ns,32767ns] . . . . . . .25

3.3.23GPS:REFerence:PULse:SAWtooth? . . . . . . . . . . . . . . . . . . 25

Micro-JLT GNSS™ User Manual

3.3.24GPS:RESET ONCE . . . . . . . . . . . . . . . . . . . . . . . . 25

3.3.25GPS:TMODe <ON|OFF|RSTSURV> . . . . . . . . . . . . . . . . . 25

3.3.26GPS:SURVey ONCE . . . . . . . . . . . . . . . . . . . . . . . 26

3.3.27GPS:SURVey:DURation <sec> . . . . . . . . . . . . . . . . . . . 26

3.3.28GPS:SURVey:VARIANCE <mm^2> . . . . . . . . . . . . . . . . . . 26

3.3.29GPS:HOLD:POSition <cm, cm, cm>. . . . . . . . . . . . . . . . . . 26

3.3.30GPS:SURVEY:STATUS? . . . . . . . . . . . . . . . . . . . . . . 26

3.3.31GPS:INITial:DATE <yyyy,mm,dd> . . . . . . . . . . . . . . . . . . 27

3.3.32GPS:INITial:TIME <hour,min,sec> . . . . . . . . . . . . . . . . . . 27

3.3.33GPS:SYSTem:SELect [GPS | SBAS | QZSS | GAL | BD ^ GLO] . . . . . . . 27

3.3.34GPS:JAMlevel? . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.3.35GPS:FWver? . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.3.36GPS?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.4 GYRO SUBSYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.4.1 GYRO:MODE <ON|OFF> . . . . . . . . . . . . . . . . . . . . . . 28

3.4.2 GYRO:TRACE <int> [0,255]. . . . . . . . . . . . . . . . . . . . . 28

3.4.3 GYRO:CAL <float,float,float,float,float,float>. . . . . . . . . . . . . . . 28

3.4.4 GYRO:CAL:COMPUTE. . . . . . . . . . . . . . . . . . . . . . . 28

3.4.5 GYRO:SENS, GYRO:EFC, and GPS:CAL:RESET . . . . . . . . . . . . 28

3.4.6 GYRO:GLOAD? . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.5 PTIME Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.5.1 PTIMe:DATE? . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.5.2 PTIMe:TIME? . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.5.3 PTIMe:TIME:STRing? . . . . . . . . . . . . . . . . . . . . . . . 29

3.5.4 PTIMe:TINTerval? . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.5.5 PTIMe:OUTput <ON|OFF> . . . . . . . . . . . . . . . . . . . . . 29

3.5.6 PTIMe:LEAPsecond? . . . . . . . . . . . . . . . . . . . . . . . 30

3.5.7 PTIMe:LEAPsecond:PENDing? . . . . . . . . . . . . . . . . . . . 30

3.5.8 PTIMe:LEAPsecond:ACCumulated?. . . . . . . . . . . . . . . . . . 30

3.5.9 PTIMe:LEAPsecond:DATE? . . . . . . . . . . . . . . . . . . . . . 31

3.5.10PTIMe:LEAPsecond:DURation? . . . . . . . . . . . . . . . . . . . 31

3.5.11PTIMe:STAMp Subsystem . . . . . . . . . . . . . . . . . . . . . 31

3.5.12PTIMe:STAMp:MODE <OFF|ASYnc|MEMory|OUTput|DIFFer> . . . . . . . 32

3.5.13PTIMe:STAMp:SOURce <GPS|EXTernal|ALL> . . . . . . . . . . . . . 33

3.5.14PTIMe:STAMp:DIFFer <ALL|EXT|GPS> . . . . . . . . . . . . . . . . 34

3.5.15PTIMe:STAMp:FILTer [OFF | REL | DUR | PPS] . . . . . . . . . . . . . 34

3.5.16PTIMe:STAMp:FILTer:PPSecond <int> [1,100] . . . . . . . . . . . . . 36

3.5.17PTIMe:STAMp:FILTer:1PPeriod <int> [1,604800] . . . . . . . . . . . . 37

3.5.18PTIMe:STAMp:LAST? . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.19PTIMe:STAMp:MEMory? . . . . . . . . . . . . . . . . . . . . . . 38

3.5.20PTIMe:STAMp:RESET . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.21PTIMe:STAMp?. . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.5.22PTIMe? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.6 SYNChronization Subsystem . . . . . . . . . . . . . . . . . . . . . . . 39

3.6.1 SYNChronization:HOLDover:DURation? . . . . . . . . . . . . . . . . 40

3.6.2 SYNChronization:HOLDover:INITiate . . . . . . . . . . . . . . . . . 40

3.6.3 SYNChronization:HOLDover:RECovery:INITiate . . . . . . . . . . . . . 40

3.6.4 SYNChronization:SOURce:MODE <GPS|EXTernal|AUTO> . . . . . . . . 40

3.6.5 SYNChronization:SOURce:MODE:EDGE <NEGative|POSitive> . . . . . . . 41

3.6.6 SYNChronization:SOURce:STATE? . . . . . . . . . . . . . . . . . . 41

3.6.7 SYNChronization:HOLDover:STATE? . . . . . . . . . . . . . . . . . 42

3.6.8 SYNChronization:TINTerval? . . . . . . . . . . . . . . . . . . . . 42

Micro-JLT GNSS™ User Manual

3.6.9 SYNChronization:TINTerval:THReshold <int> [50,2000] . . . . . . . . . .42

3.6.10SYNChronization:IMMEdiate . . . . . . . . . . . . . . . . . . . . . 42

3.6.11SYNChronization:FEEstimate? . . . . . . . . . . . . . . . . . . . . 43

3.6.12SYNChronization:LOCKed? . . . . . . . . . . . . . . . . . . . . . 43

3.6.13SYNChronization:OUTput:1PPS:RESET <ON|OFF>. . . . . . . . . . . .43

3.6.14SYNChronization:OUTput:1PPS:RESET? . . . . . . . . . . . . . . . .43

3.6.15SYNChronization:OUTput:1PPS:WIDTH <int> <ms | us> [100us, 500ms] . . . 43

3.6.16SYNChronization:HEAlth? . . . . . . . . . . . . . . . . . . . . . . 44

3.6.17SYNChronization? . . . . . . . . . . . . . . . . . . . . . . . . .44

3.7 DIAGnostic Subsystem. . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.7.1 DIAGnostic:ROSCillator:EFControl:RELative? . . . . . . . . . . . . . . 45

3.7.2 DIAGnostic:ROSCillator:EFControl:ABSolute? . . . . . . . . . . . . . .45

3.7.3 DIAGnostic:LIFetime:COUNt? . . . . . . . . . . . . . . . . . . . .45

3.7.4 DIAGnostic? . . . . . . . . . . . . . . . . . . . . . . . . . . .45

3.8 MEASURE Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . .46

3.8.1 MEASure:VOLTage? . . . . . . . . . . . . . . . . . . . . . . . . 46

3.8.2 MEASure:POWersupply? . . . . . . . . . . . . . . . . . . . . . . 46

3.8.3 MEASure:POWersupply:VOSCillator? . . . . . . . . . . . . . . . . . 46

3.8.4 MEASure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.9 SYSTEM Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.9.1 SYSTem:COMMunicate:SERial:ECHO <ON|OFF> . . . . . . . . . . . . 47

3.9.2 SYSTem:COMMunicate:SERial:PROmpt <ON|OFF> . . . . . . . . . . . 47

3.9.3 SYSTem:COMMunicate:SERial:BAUD <9600|19200|38400|57600|115200> . . 47

3.9.4 SYSTem:STATus? . . . . . . . . . . . . . . . . . . . . . . . . . 47

3.9.5 SYSTem:FACToryReset ONCE . . . . . . . . . . . . . . . . . . . 47

3.9.6 SYSTem:CPURESET. . . . . . . . . . . . . . . . . . . . . . . . 47

3.9.7 SYSTem:ISP . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.10SERVO Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . .48

3.10.1SERVo:FASTlock <int> [1,20] . . . . . . . . . . . . . . . . . . . . 48

3.10.2SERVo:FALEngth <int> [100,20000] . . . . . . . . . . . . . . . . . .49

3.10.3SERVo:COARSedac <int> [0,255] . . . . . . . . . . . . . . . . . . . 49

3.10.4SERVo:DACGain . . . . . . . . . . . . . . . . . . . . . . . . . 50

3.10.5SERVo:EFCScale <float> [0.0,500.0]. . . . . . . . . . . . . . . . . .50

3.10.6SERVo:EFCDamping <int> [2,4000] . . . . . . . . . . . . . . . . . . 50

3.10.7SERVo:SLOPe <NEG|POS> . . . . . . . . . . . . . . . . . . . . .50

3.10.8SERVo:TEMPCOmpensation . . . . . . . . . . . . . . . . . . . . . 50

3.10.9SERVo:AGINGcompensation <float> [-10.0,10.0] . . . . . . . . . . . . . 51

3.10.10SERVo:PHASECOrrection <float> [-500.0,500.0] . . . . . . . . . . . . 51

3.10.11SERVo:1PPSoffset <int> <ns> [-5000000,5000000] . . . . . . . . . . . 51

3.10.12SERVo:TRACe <int> [0,255] . . . . . . . . . . . . . . . . . . . . 51

3.10.13SERVo? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4 Firmware Upgrade Instructions . . . . . . . . . . . . . . . . . . 53

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.2 ISP Flash Loader Utility installation . . . . . . . . . . . . . . . . . . . . . 53

4.3 Putting the PCB into In-Circuit Programming (ISP) mode . . . . . . . . . . . . 53

4.4 Downloading the firmware . . . . . . . . . . . . . . . . . . . . . . . . 54

4.4.1 Using the JLTerm Programming Terminal . . . . . . . . . . . . . . . . 54

4.4.2 Using the Flash Magic Programming Utility . . . . . . . . . . . . . . . 57

4.4.3 Using the Flash Magic Classic Version . . . . . . . . . . . . . . . . . 58

4.5 Verifying Firmware Update . . . . . . . . . . . . . . . . . . . . . . . . 61

Micro-JLT GNSS™ User Manual

5 GPSCon Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.3 Using GPSCon . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.3.1 Setting the options. . . . . . . . . . . . . . . . . . . . . . . . . 63

5.3.1.1 Communication Parameters . . . . . . . . . . . . . . . . . . 64

5.3.1.2 Auxiliary Parameters . . . . . . . . . . . . . . . . . . . . 64

5.3.1.3 Traces Parameters . . . . . . . . . . . . . . . . . . . . . 65

5.3.2 Sending manual commands to the receiver . . . . . . . . . . . . . . . 67

5.3.3 Using the Mouse in the Graph Window. . . . . . . . . . . . . . . . . 67

5.3.4 Exporting the graphics . . . . . . . . . . . . . . . . . . . . . . . 69

5.4 Interpreting the Data . . . . . . . . . . . . . . . . . . . . . . . . . . 70

6 Certification and Warranty . . . . . . . . . . . . . . . . . . . . 73

6.1 Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.1.1 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.1.2 Limitation of Warranty . . . . . . . . . . . . . . . . . . . . . . . 73

6.1.3 Exclusive Remedies . . . . . . . . . . . . . . . . . . . . . . . . 74

7 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . 75

7.1 Revision Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Micro-JLT GNSS™ User Manual

Introduction

1.1 Overview

The Micro-JLT GNSS™ board is the latest generation GNSDO™ product from Jackson Labs

Technologies, Inc. and is based on the popular Mini-JLT GPSDO product line. As an example,

Figure 1.1 displays an image of a single oven OCXO option for the Micro-JLT GNSS™. The

Micro-JLT GNSS™ supports three-concurrent multi-GNSS tracking by using a latest generation

concurrent GPS/Glonass/Galileo/BeiDou/QZSS/SBAS capable fixed-position GNSS timing

receiver, as well as optimizes phase noise performance, power supply consumption, cost, and

lead-time, while adding differential interfacing for robustness in adverse environmental conditions.

For the purposes of this discussion the word GNSDO is used interchangeably with GPSDO. The

board is designed for long life-time, high volume production with the industries’ lowest price point

in its class. The Micro-JLT GNSS™ is designed for fast warm-up with optimum stability with

excellent ADEV and Phase Noise performance for high-volume, low-cost applications that can

encounter the harshest environments.

The Micro-JLT GNSS™ GNSDO uses a multi-GNSS receiver that can run in stationary (Position

Hold) mode as well as 3D mobile mode to discipline either a single oven or optional double oven

OCXO local oscillator to better than 0.1ppb frequency accuracy typically. It supplies one 10MHz

output with ultra-low phase-noise, exceptional ADEV performance, and very low spurs and

harmonics. The board includes an RS-422/TTL control port for NMEA and SCPI communication,

and an LVDS 1PPS timing output driven by the on-board ultra-low-jitter holdover oscillator. The

board operates from a single +5.5V nominal supply with 5.2V to 6.0V range (a 5.0V +/-0.2V

operating range can be optionally ordered), and has connector pins to indicate GNSS and oscillator

LOCK and ALARM events. The board includes a high-performance GNSS receiver that can acquire

and track up to 72 GNSS signals down to a state of the art –167dBm (GPS and GLONASS), a

latest-generation low-power 32-bit processor that runs a Real Time OS, one 10MHz +8.5dBm Sine

Wave output, 1PPS UTC synchronized LVDS output, RS-422/TTL serial control interface, and

precision voltage references and DACs. The board also includes the latest generation multi-level

power supply management and conditioning for low power-consumption and extremely high

power-supply noise and stability rejection ratios. The Micro-JLT GNSS™ builds upon the legacy of

Jackson Labs Technologies, Inc. tens’ of thousands of fielded GPSDO units.

Micro-JLT GNSS™ User Manual

Figure 1.1 Micro-JLT GNSS™ SOCXO GNSDO

1.2 General Safety Precautions

The following general safety precautions must be observed during all phases of operation of this

instrument. Failure to comply with these precautions or with specific warnings elsewhere in this

manual violates safety standards of design manufacture, and intended use of the instrument. Jackson

Labs Technologies, Inc. assumes no liability for the customer’s failure to comply with these

requirements.

1.2.1 Antenna Lightning Protector

Always use a UL approved and properly installed GNSS Antenna Lightning protector on the coaxial

GNSS antenna feed to prevent damage, injury, and/or death in case of a lightning strike.

1.2.2 Grounding

To avoid damaging the sensitive electronic components in the Micro-JLT GNSS™ GNSDO 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 sure to connect the DC power to the device following the polarity indicated in Section 2.1 . Do

not reverse the power pins as this will cause serious damage to the circuit board.

Micro-JLT GNSS™ User Manual

1.2.4 Environmental Conditions

This instrument is intended for indoor use. It is designed to operate at a maximum relative

non-condensing humidity of 95% and at altitudes of up to 50,000 meters. Refer to the specifications

tables for the ac mains voltage requirements and ambient operating temperature range.

Micro-JLT GNSS™ User Manual

Quick-Start

Instructions

2.1 Powering Up the Unit

To operate the unit, simply follow these two steps:

1) Connect a 3.3V-compatible GNSS antenna to SMA connector J2. Use an appropriate

lightning surge suppressor on the antenna cable. The Micro-JLT GNSS™ board will supply

a current-limited 3.3V power to the antenna

2) Connect +5.5V (-0.3V/+0.5V) DC Power to J1 pin 10 and pin 12 on the unit, and ground

to pin 2 and pin 9 of J1

[The unit will consume up to 8W of power during oscillator warmup]

The unit will now lock to GNSS signals (Red LED D2 is blinking to indicate that the GNSS receiver

has a proper fix) and will indicate proper lock and no events pending when the Green LED D2 goes

on, with the Red LED D2 intermittently blinking as well. Once the green LED D2 is on, the unit will

output 10MHz with significantly 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, timing

accuracy, and incorrect GNSS fixes. The unit must be configured to mobile

3D mode using the GPS:TMODe OFF command when used in an

application where the antenna position can move during normal operation.

Using the Auto Survey process and Position Hold mode allows the unit to

over-determine the timing solution. It also allows TRAIM operation which

will result in a higher timing stability and more robust GNSS reception in

challenged environmental conditions such as under foliage, in urban

canyons, etc.

Please note that the GNSS receiver establishes the internal antenna gain right after

power-on, so for proper operation the GNSS antenna should always be connected prior

to turning on the +5.5V prime power.

Micro-JLT GNSS™ User Manual

Connect a terminal program (TeraTerm is recommended) to the unit via an RS-422 or TTL, (the

choice depends on your order option), to a USB serial connector to the appropriate pins on J1 with a

setting of 115.2KB 8N1 and no flow-control. You may also download the GPSCon program

discussed in Chapter 5 from the JLT support website page for free.

WARNING: Do not connect RS-232 serial levels to connector J1. The unit may become

damaged from RS-232 serial levels on connector J1 as the default configuration is

RS-422 differential or TTL levels.

Try some of these typical SCPI commands or refer to Chapter 3 for full list of SCPI commands:

HELP?

SYSTem:STATus?

GPS?

SYNChronization?

MEASure?

DIAGnostic?

*IDN?

2.1.1 PCB Photos

The Micro-JLT GNSS™ PCB connectors and indicators are shown in Figure 2.1.

Figure 2.1 Micro-JLT GNSS™ Single Oven PCB

A Micro-JLT GNSS™ unit with a double oven OCXO is shown in Figure 2.2.

Micro-JLT GNSS™ User Manual

Figure 2.2 Micro-JLT GNSS™ Double Oven PCB

2.1.2 Mechanical Drawings

The following drawings show the mechanical dimensions and the pinout of the Micro-JLT GNSS™

PCB:

Figure 2.3 Micro-JLT GNSS™ Mechanical Dimensions

Micro-JLT GNSS™ User Manual

Table 2.1 shows the Micro-JLT GNSS™ revision 1.0 hardware pin descriptions

Table 2.1 Micro-JLT GNSS™ hardware connectors

Ref Name Function Specification Description

J1 Pin 1 ISP# Enables In System

Programming mode

(ISP)

0V to 3.3V, pulled-high by 4.7K

resistor

Pull to Ground during power-on to

set processor into ISP mode.

Leave floating during normal

operation

J1 Pin 2 Ground Ground Ground Ground

J1 Pin 3 1PPS OUT-P LVDS 1PPS positive

signal output

LVDS level, positive signal Flywheel OCXO-generated 1PPS

output in LVDS level

J1 Pin 4 1PPS OUT-N LVDS 1PPS negative

signal output

LVDS level, negative signal Flywheel OCXO-generated 1PPS

output in LVDS level

J1 Pin 5 TX-Serial-P RS-422 positive signal

output / TXD_TTL

RS-422 level, positive signal /

TTL level

RS-422 positive signal / TTL

NMEA and SCPI communications

port output from unit

J1 Pin 6 TX-Serial-N RS-422 negative signal

output

RS-422 level, negative signal RS-422 NMEA and SCPI

communications port output from

unit, negative signal

J1 Pin 7 RX-Serial-P RS-422 positive signal

input / RXD_TTL

RS-422 level, positive signal /

TTL level

RS-422 positive signal / TTL SCPI

communications port input to unit

J1 Pin 8 RX-Serial-N RS-422 negative signal

input

RS-422 level, negative signal RS-422 SCPI communications

port input to unit, negative signal

J1 Pin 9 Ground Ground Ground Ground

J1 Pin 10 +5.5V Power Prime Power Input +5.5V, -0.3V +0.5V max Prime Power input. 2.6W typical

steady-state, up to 8W during

warmup. Connect to J1 pin 12

J1 Pin 11 LOCK-OK/

EVENT#

Indicates Event, Alarm,

and LOCK-OK

conditions

3.3V == unit locked and healthy

0V == Event or Alarm exist

Output will turn on (3.3V) when

unit is warmed up, locked to

GNSS, and healthy. Output will

turn off (0V) when an event is

pending, and alarm happened, or

no GNSS signal is present. Query

the SYNC:HEALTH? indicator for

more details on the event/alarm

state.

J1 Pin 12 +5.5V Power Prime Power Input +5.5V, -0.3V +0.5V max Prime Power input. 2.6W typical

steady-state, up to 8W during

warmup. Connect to J1 pin 10

J2 GNSS Antenna Antenna Input L1, +3.3V output, <=40mA Supplies 3.3V to an external

active GNSS antenna

J3 10MHz output 10MHz Sine Wave

Output

+8.5dBm, +/-0.5 dBm 10MHz output driven by on-board

OCXO. Does not require a load if

unused.

Micro-JLT GNSS™ User Manual

2.1.3 Notes on Signal Interfacing and J1 Connector

Connector J1 is a straight-up, 12-pin dual row 2mm spacing Hirose connector part number:

DF11-12DP-2DSA(01). A right angle type board-to-board connector may also be optionally stuffed

at the factory for high-volume custom orders. Pin out descriptions are listed in Table 2.1.

The optional LOCK_OK_OUT signal on J1 pin 11 is a 3.3V LVCMOS signal, and thus require a

series resistor of typically 390 to 470 Ohms when used to drive an external signalling LED.

The serial port RX and TX lines cannot be directly connected to a DB9 connector as these are driven

with RS-422/TTL signal levels. Connecting these pins to an RS-232 serial interface may damage the

board. External RS-422/TTL to RS-232 converters may be used (RS-485 converters will typically

not work as they are bi-directional and power-down when no transmission is active). The output of

the RS-422/TTL to RS-232 converter may then be connected to standard RS-232 USB connector

adaptors. Signalling on the RS-422 serial port should be done in differential mode, although the

RS-422 TX positive output (TXD_TTL) on pin 5 of connector J1 is equivalent to a standard 3.3V

TTL serial output, and may be used as such when used without termination.

If the Micro-JLT GNSS™ is ordered with the TTL option, pin 5 of connector J1 (TXD_TTL), pin 7

of connector J1 (RXD_TTL), and a ground (pin 2 or 9 of connector J1) pin should be connected to

the TTL-to-RS-232 / TTL-to-USB converter.

Connect an active GNSS GPS/Glonass antenna that is compatible to 3.3V antenna power with

typically between 10dB to 40dB gain and less than 1.5dB NF, and connect this antenna prior to

turning-on the board. Use a lightning arrestor on the antenna feed for safety and to prevent damage,

injury, or death in case of a lightning strike.

2.1.4 Coaxial Connectors

The GNSS antenna connector and the 10MHz connector on the Micro-JLT GNSS™ board are

generic SMA female types. Optionally the female MCX connector type can be ordered.

J4 Pin 1 ISP# Enables ISP mode.

Wired in paralell to J1

Pin 1

0V to 3.3V, pulled-high by 4.7K

resistor

Pull to Ground during power-on to

set processor into ISP mode.

Leave floating during normal

operation. May be momentarily

shorted during power-on to Pin 2

of J4 using tweezers etc.

J4 Pin 2 Ground Ground Ground Ground

J4 Pin 3 External PPS

reference Input

Optional PPS External

Reference input

-0.5V to 5.0V with a

recommended <10ns rise/fall

time on the signal. Terminated

by 5K pull-down resistor.

Optional external PPS reference

input in CMOS TTL format.

Micro-JLT GNSS™ User Manual

2.2 Power

The unit is powered from a +5.2V to +6V max. DC source, with +5.5V nominal voltage. The current

is typically less than 0.6A at 5.5V. Connect a clean +5.5V power supply to pins 10 and 12 of J1, and

ground to pin 2 and 9 of J1. The unit may also be optionally ordered with 5.0V +/-10% supply range

for large volume custom orders.

2.3 Concurrent-GNSS Capabilities

The Micro-JLT GNSS™ is capable of simultaneously receiving up to three concurrent GNSS

systems at one time. Concurrent GNSS operation aids performance by allowing reception of 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 GNSS systems can increase immunity against jamming which often occurs at only one

carrier frequency.

The multiple GNSS systems each have their own reference time and representation of UTC. For

example, GPS uses the GPS time standard and provides a method to convert GPS time to UTC as

defined by the US Naval Observatory (USNO). GLONASS, Galileo and BeiDou have similar

reference times and UTC definitions. The Micro-JLT GNSS™ automatically adjusts for offsets

between the different GNSS time reference standards and synchronizes the 1PPS output to UTC

(USNO) when GPS is being received. If GPS is not being received, the 1PPS output is synchronized

to the best representation of UTC (USNO) available.

The selection of GNSS systems is made with the GPS:SYST:SEL command as detailed in

Section 3.3.33 . Because these systems operate at different carrier frequencies with different

bandwidths, it is necessary to use a GNSS antenna that is designed to receive all the required GNSS

systems. Please note that the new and emerging Galileo system is now functional, and uses the same

carrier frequency as GPS L1, albeit with a wider bandwidth. In our experience Galileo sats can be

received with good C/No carrier to noise figures (>40dB) with standard legacy GPS antennae and

distribution amplifiers/splitters. JLT thus recommends enabling at a minimum GPS and Galileo

concurrently with the command: GPS:SYST:SEL GPS GAL, see also Section 3.3.33 . Using other

GNSS systems such as Glonass will require an antenna system designed to support Glonass signals.

As of November 2019, JLT received multiple reports on SBAS satellites causing timing issue on the

GPSDO units around the world. Until further notice, JLT recommends disabling the SBAS in

GPS:SYST:SEL command to avoid potential timing issue or monitoring the timing stability of

Micro-JLT GNSS™ unit if SBAS is desired.

The internal GNSS receiver can track up to three different GNSS systems concurrently, such as GPS,

Galileo, Glonass, and SBAS at the same time, however only two different carrier frequencies may be

received at any given time, so BeiDou and Glonass cannot be enabled concurrently when either GPS,

Galileo, or QZSS are simultaneously enabled as that would require tracking three different carrier

frequencies.

Attempting to configure an invalid combination of GNSS systems with the GPS:SYST:SEL

command will result in a Command Error response with no change to the configuration.

Micro-JLT GNSS™ User Manual

2.4 Connecting the GNSS Antenna

Connect the GNSS antenna to the SMA connector J2. Caution: use a Lightning Arrestor on your

Antenna setup. Use an amplified GNSS antenna that is 3.3V LNA compatible. The Micro-JLT

GNSS™ GNSDO GNSS receiver is a 72 channel high-sensitivity multi-GNSS receiver with very

fast lock time.

The Micro-JLT GNSS™ unit is factory set to use Position Hold mode, and will initiate an Auto

Survey process after power-on to establish its new position. The Auto Survey process may last

up to 3 hours. The units’ antenna should not be moved when set to Position Hold mode. Please

set the unit to 3D mobile mode using the GPS:TMODe OFF command in Section 3.3.25 when

the unit is to be used in a mobile environment where the antenna position can change more

than 1 foot during operation.

The Micro-JLT GNSS™ is capable of generating standard navigation messages (see GPS:GPGGA,

GPS:GPZDA, GPS:GPGSV, GPS:PASHR, and GPS:GPRMC RS-422/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(USNO). This

1PPS signal is used to frequency-lock the 10MHz output of the Micro-JLT GNSS™ GNSDO to

UTC, thus disciplining the unit’s 10MHz frequency output to the US Naval master clock for very

high frequency accuracy (typically better than 10 digits of frequency accuracy when locked to GNSS

signals).

2.5 Remote serial control

The unit is controlled via the RS-422/TTL serial port at 115200 baud, 8N1. Other baud rates can be

set via the SCPI command found in Section 3.9.3 .

Attach the Micro-JLT GNSS™ unit to your PC’s terminal program, the cost-free Jackson Labs

GPSCon software package available on the JLT website support page (see Chapter 5), or a

third-party freeware Windows-based application program called Z38xx also available on the JLT

website support page. The GPSCon and Z38xx programs can be used to control and track the

performance of the Micro-JLT GNSS™.

2.6 Loop parameter adjustment

All loop parameters can be controlled via the RS-422/TTL serial port.

Loop parameters are optimized for the OCXO on the board, and changing the factory settings may

result in the unit’s performance to deteriorate. By default the settings are optimized for quick

frequency error correction and slow phase offset error correction, favoring the highest possible

frequency accuracy and ADEV performance over fast phase error corrections.

The commands to control the loop parameters are part of the servo? command. See also the SERVO

Subsystem section below.

The individual commands are:

EFC Scale: this is the proportional gain of the PID loop. Higher values will give quicker

convergence, and faster locking of the GPS time (lower loop time constant), lower values give less

noise. Values between 0.7 (good double oven OCXO) and 6.0 (simple single-oven OCXO) are

typical.

Micro-JLT GNSS™ User Manual

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 Micro-JLT GNSS™ 1PPS signal and the UTC 1PPS signal as generated by the GNSS receiver.

Set higher values for tighter phase-following at the expense of frequency stability. Typical values

range from 4 - 30. Setting this value too high may cause loop instability.

A well-compensated unit will show performance similar to the plot shown in Figure 2.4 when

experiencing small perturbations:

Figure 2.4 Micro-JLT GNSS™ phase compensation plot

Micro-JLT GNSS™ User Manual

SCPI-Control Quick

Start Instructions

3.1 Introduction

The SCPI (Standard Commands for Programmable Instrumentation) subsystem is accessed via the

RS-422/TTL serial interface and a terminal program. By default the terminal settings are 115200,

8N1, no flow-control.

There are a number of commands that can be used as listed below. Most of these are identical or

similar to 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 Micro-JLT GNSS™

GNSDO.

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. Note that the

symbols ‘<’, ‘>’, ‘[’, ‘]’, ‘|’, and ‘,’ in the parameter field listed in some commands of Chapter 3 are

used for ranging or separating ONLY. Do not include these symbols when sending the SCPI

commands to avoid Command Error response.

3.2 General SCPI Commands

3.2.1 Quick Start Commands

For a quick start, try the following SCPI serial port commands.

Note that all lower case letters in SCPI commands throughout the User Manual are optional. The

abbreviated version of the SCPI commands such as SYST:STAT? and SYNC? will also work.

HELP?

SYSTem:STATus?

GPS?

SYNChronization?

Micro-JLT GNSS™ User Manual

MEASure?

DIAGnostic?

3.2.2 *IDN?

This query outputs an identifying string. The response will show the following information:

The serial number field represents the unique identifier of the 32-bit processor.

An example response of this command is provided below:

Jackson Labs, Micro-JLT, 0D02001C AAB22D23 57FD8E0F F50007C6, 0.46

3.2.3 HELP?

This query returns a list of the commands available for the Micro-JLT GNSS™ GNSDO.

3.3 GPS Subsystem

Note: Please note that Micro-JLT GNSS™ displays antenna height in MSL Meters rather than in

GPS Meters on all commands that return antenna height [the legacy Fury GPSDO uses GPS height].

The NMEA position fixes are in the WGS84 coordinate system, while the X,Y, and Z velocity vectors

are given in the ECEF 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?

GPS:RESET ONCE

GPS:REFerence:ADELay <float> <s | ns > [-32767ns,32767ns]

GPS:REFerence:PULse:SAWtooth?

GPS:TMODe <ON|OFF|RSTSURV>

GPS:SURVey ONCE

GPS:SURVEY:STATUS?

GPS:SURVey:DURation <sec>

GPS:SURVey:VARIANCE <mm^2>

GPS:HOLD:POSition <cm, cm, cm>

GPS:DYNAMic:MODE <int> [0,7]

GPS:DYNAMic:MODE?

GPS:DYNAMic:MODE 8 (Automatic Dynamic Mode)

GPS:DYNAMic:STATe?

GPS:GPRMC <int> [0,255]

GPS:GPGGA <int> [0,255]

GPS:GGASTat <int> [0,255]

Jackson Labs Micro-JLT GNSS User manual

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