Jackson labs Mini-jlt gnss User manual

Mini-JLT GNSS™

User Manual

Document: 80200549

Version: 1.1

Date: 28 August, 2017

Mini-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 . . . . . . . . . . . . . . . . . . . . . . 2

2 Quick-Start Instructions . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Powering Up the Unit . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1.1 PCB Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1.2 Mechanical Drawings . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1.3 Notes on Signal Interfacing. . . . . . . . . . . . . . . . . . . . . . 6

2.1.4 Coaxial Connectors. . . . . . . . . . . . . . . . . . . . . . . . . 7

2.2 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Multi-GNSS Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 Connecting the GNSS Antenna . . . . . . . . . . . . . . . . . . . . . . 8

2.5 Remote serial control . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.6 Loop parameter adjustment . . . . . . . . . . . . . . . . . . . . . . . . 8

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

3.3.12GPS:GYRO . . . . . . . . . . . . . . . . . . . . . . . . . . .16

3.3.13GPS:GYRO:CAL . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.3.14GPS:DYNAMic:MODE . . . . . . . . . . . . . . . . . . . . . . . 18

3.3.15GPS:DYNAMic:MODE 8 (Automatic Dynamic Mode) . . . . . . . . . . . 19

3.3.16GPS:DYNAMic:STATe? . . . . . . . . . . . . . . . . . . . . . . . 21

3.3.17GPS:REFerence:ADELay <float> <s | ns > [-32767ns,32767ns] . . . . . . .21

3.3.18GPS:REFerence:PULse:SAWtooth? . . . . . . . . . . . . . . . . . . 21

3.3.19GPS:RESET ONCE . . . . . . . . . . . . . . . . . . . . . . . . 21

3.3.20GPS:TMODe <ON|OFF|RSTSURV>. . . . . . . . . . . . . . . . . . 21

3.3.21GPS:SURVey ONCE. . . . . . . . . . . . . . . . . . . . . . . . 22

3.3.22GPS:SURVey:DURation <sec> . . . . . . . . . . . . . . . . . . . . 22

3.3.23GPS:SURVey:VARIANCE <mm2> . . . . . . . . . . . . . . . . . .22

Mini-JLT GNSS™ User Manual

3.3.24GPS:HOLD:POSition <cm, cm, cm> . . . . . . . . . . . . . . . . . 22

3.3.25GPS:SURVEY:STATus:DURation? . . . . . . . . . . . . . . . . . . 22

3.3.26GPS:SURVEY:STATUS? . . . . . . . . . . . . . . . . . . . . . . 22

3.3.27GPS:INITial:DATE <yyyy,mm,dd> . . . . . . . . . . . . . . . . . . 23

3.3.28GPS:INITial:TIME <hour,min,sec> . . . . . . . . . . . . . . . . . . 23

3.3.29GPS:SYSTem:SELect [GPS | SBAS | QZSS | GAL | BD ^ GLO] . . . . . . . 23

3.3.30GPS:JAMlevel? . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.31GPS:FWver? . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3.32GPS?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.4 GYRO SUBSYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.4.1 GYRO:MODE <ON | OFF> . . . . . . . . . . . . . . . . . . . . . 24

3.4.2 GYRO:TRACE <int> [0,255]. . . . . . . . . . . . . . . . . . . . . 24

3.4.3 GYRO:CAL <float,float,float,float,float,float>. . . . . . . . . . . . . . . 24

3.4.4 GYRO:CAL:COMPUTE. . . . . . . . . . . . . . . . . . . . . . . 25

3.4.5 GYRO:SENS, GYRO:EFC, and GPS:CAL:RESET . . . . . . . . . . . . 25

3.4.6 GYRO:GLOAD? . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5 PTIME Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5.1 PTIMe:DATE? . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5.2 PTIMe:TIME? . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.5.3 PTIMe:TIME:STRing? . . . . . . . . . . . . . . . . . . . . . . . 26

3.5.4 PTIMe:TINTerval? . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.5.5 PTIMe:LEAPsecond? . . . . . . . . . . . . . . . . . . . . . . . 26

3.5.6 PTIMe:LEAPsecond:PENDing? . . . . . . . . . . . . . . . . . . . 26

3.5.7 PTIMe:LEAPsecond:ACCumulated?. . . . . . . . . . . . . . . . . . 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:THReshold [50,2000] . . . . . . . . . . . . 28

3.6.8 SYNChronization:IMMEdiate. . . . . . . . . . . . . . . . . . . . . 28

3.6.9 SYNChronization:FEEstimate? . . . . . . . . . . . . . . . . . . . . 28

3.6.10SYNChronization:LOCKed? . . . . . . . . . . . . . . . . . . . . . 29

3.6.11SYNChronization:OUTput:1PPS:RESET [ON|OFF] . . . . . . . . . . . 29

3.6.12SYNChronization:health? . . . . . . . . . . . . . . . . . . . . . . 29

3.6.13SYNChronization?. . . . . . . . . . . . . . . . . . . . . . . . . 30

3.7 DIAGnostic Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.7.1 DIAGnostic:ROSCillator:EFControl:RELative? . . . . . . . . . . . . . . 30

3.7.2 DIAGnostic:ROSCillator:EFControl:ABSolute? . . . . . . . . . . . . . . 30

3.7.3 DIAGnostic:LIFetime:COUNt? . . . . . . . . . . . . . . . . . . . . 30

3.8 MEASURE Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.8.1 MEASure:VOLTage?. . . . . . . . . . . . . . . . . . . . . . . . 31

3.8.2 MEASure:CURRent?. . . . . . . . . . . . . . . . . . . . . . . . 31

3.8.3 MEASure? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.9 SYSTEM Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.9.1 SYSTem:COMMunicate . . . . . . . . . . . . . . . . . . . . . . 31

3.9.1.1 SYSTem:COMMunicate:SERial:ECHO . . . . . . . . . . . . . 31

Mini-JLT GNSS™ User Manual

3.9.1.2 SYSTem:COMMunicate:SERial:PROmpt . . . . . . . . . . . . . 31

3.9.1.3 SYSTem:COMMunicate:SERial:BAUD . . . . . . . . . . . . . .32

3.9.2 SYSTem:STATus? . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.9.3 SYSTem:FACToryReset ONCE . . . . . . . . . . . . . . . . . . . 32

3.10SERVO Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . .32

3.10.1SERVo:FASTlock . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.10.2SERVo:FALEngth . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.10.3SERVo:COARSeDac . . . . . . . . . . . . . . . . . . . . . . . .33

3.10.4SERVo:DACGain . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.10.5SERVo: EFCScale . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.10.6SERVo:EFCDamping . . . . . . . . . . . . . . . . . . . . . . . . 34

3.10.7SERVo:SLOPe . . . . . . . . . . . . . . . . . . . . . . . . . .34

3.10.8SERVo:TEMPCOmpensation . . . . . . . . . . . . . . . . . . . . . 34

3.10.9SERVo:AGINGcompensation. . . . . . . . . . . . . . . . . . . . . 34

3.10.10SERVo:PHASECOrrection . . . . . . . . . . . . . . . . . . . . . 34

3.10.11SERVo:1PPSoffset . . . . . . . . . . . . . . . . . . . . . . . . 35

3.10.12SERVo:TRACe . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.10.13SERVo? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4 Firmware Upgrade Instructions . . . . . . . . . . . . . . . . . . 37

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.2 ISP 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 Using GPSCon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.3.1 Setting the options . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.3.1.1 Communication Parameters . . . . . . . . . . . . . . . . . .46

5.3.1.2 Auxiliary Parameters . . . . . . . . . . . . . . . . . . . . . 46

5.3.1.3 Traces Parameters . . . . . . . . . . . . . . . . . . . . . 47

5.3.2 Sending manual commands to the receiver . . . . . . . . . . . . . . .49

5.3.3 Using the Mouse in the Graph Window . . . . . . . . . . . . . . . . .49

5.3.4 Exporting the graphics . . . . . . . . . . . . . . . . . . . . . . .51

5.4 Interpreting the Data. . . . . . . . . . . . . . . . . . . . . . . . . . .52

6 Certification and Warranty . . . . . . . . . . . . . . . . . . . . .55

6.1 Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6.1.1 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55

6.1.2 Limitation of Warranty . . . . . . . . . . . . . . . . . . . . . . . . 55

6.1.3 Exclusive Remedies . . . . . . . . . . . . . . . . . . . . . . . .56

Mini-JLT GNSS™ User Manual

Introduction

1.1 Overview

The Mini-JLT GNSS board adds multi-GNSS support to the original Jackson Labs Mini-JLT GPSDO

with the addition of a GPS/Glonass/Galileo/BeiDou/QZSS/SBAS fixed-position timing receiver.

Jackson Labs Technologies, Inc. originally designed the Mini-JLT™ board to address a market

demand for replacing the end-of-life Trimble Navigation Limited Mini-T™ GPSDO units used in

existing customer projects. The board was designed to be form-fit-function compatible to the Trimble

units, with the exception of adding various features such as a 1PPS external input, 3-axis on-board

accelerometer, USB communication, internal antenna power supply, wide-range main power supply,

extended temperature range, lower overall height (0.8 inches vs. 0.5 inches above the PCB), and a

significantly improved 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 outputs. The board includes both TTL-level (RS-232 serial levels

optional) and USB serial control ports for NMEA and SCPI communication. The board operates

from a single +5V supply with 4.0V to 6.0V range, and has connectors to indicate GNSS and

External-Reference lock/presence. 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 32bit processor that runs a Real Time OS, one10MHz +5dBm legacy output, one optional 10MHz

+13dBm output, 1PPS UTC synchronized CMOS output, TTL/USB or optional RS-232 serial

control interfaces, and precision voltage references and DACs.

Mini-JLT GNSS™ User Manual

Figure 1.1 Mini-JLT GNSS™ GPSDO

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 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 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.

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.

Mini-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 or 5V-compatible GNSS antenna to SMA connector J4. The antenna can

be passive or active. The Mini-JLT GNSS™ board will supply 3.3V to the antenna by

default, and this can be increased to up to 5.5V through the external antenna power supply

pin 5 of connector J1

2) Connect +5V (+/-1V) DC Power to J1 pin 6 on the unit, and ground to pin 4 of J1

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

The unit will now lock to GNSS signals (Red LED D1 is blinking when satellites are being received)

and will indicate proper lock and no events pending when the Green LED D1 goes on. Once the

green LED D1 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 and timing

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

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, and also allows TRAIM operation which

will result in slightly 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 +5V power.

Mini-JLT™ User Manual

Connect a terminal program (TeraTerm is recommended) to the unit via the TTL serial connector

pins on J1, or to the USB serial port, both with 115.2KB 8N1 and no flow-control.

WARNING: Do not connect RS-232 serial levels to connector J1, the unit may get

damaged from RS-232 serial levels 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 GNSS™ Single Oven PCB

2.1.2 Mechanical Drawings

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

PCB:

Mini-JLT GNSS™ User Manual

Figure 2.2 Mini-JLT GNSS™ Mechanical Dimensions

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

Table 2.1 Mini-JLT GNSS™ hardware connectors

Ref Name Function Specification Description

J1 Pin 1 1PPS In Optional external 1PPS

Input

0V to 5V, pulled-low by 4.7K

resistor

Alternate 1PPS reference input

J1 Pin 2 Serial TX Serial Transmit Output 3.3V LVCMOS (RS-232 serial

optional)

Serial Transmit output for NMEA and

SCPI sentences, internally

connected to USB TX signal

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 supplied to the VANT

pin. Both the internal 3.3V and the

external VANT supply are diode-ored

and protected against each other.

The VANT current is fused by a

100mA self-resetting fuse on the

PCB.

J1 Pin 6 +5V Power Main Power Supply 4.0V to 6.0V range, 5V nominal Supplies power to the unit and the

OCXO. Up to 8W are required during

warmup. Range is 5V +/-1.0V

Mini-JLT™ User Manual

2.1.3 Notes on Signal Interfacing

The optional LOCK_OK_OUT is a 3.3V LVCMOS signal, and thus require a series resistor of

typically 390 to 470 Ohms when used to drive an external LED.

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

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

J5 Pin 3 LOCK OK Lock and Event#

indicator

3.3V LVCMOS 3.3V: Unit Locked to GPS, and no

events pending

0V: Event is pending (events can

be queried via the sync:health?

command). Not stuffed by default

for legacy compatibility

J5 Pin 2 ISP# and GPS

Detect

Enable ISP mode,

indicate GPS signal

detection

3.3V LVCMOS open collector,

pulled to +3.3V via 4.7K resistor.

Do not load this pin to

ground, as this would enable

ISP mode during power on.

Use an LVCMOS input to

query the state of this pin.

Enables In System Programming

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 external antenna

power feed on J1. Fused with 100mA

self-resetting fuse

J6 10MHz output 10MHz Sine Wave

Output

+13dBm, +/-3dBm 10MHz output from isolated

distribution amplifier, driven by

on-board OCXO. Not stuffed by

default for legacy compatibility

J2 10MHz output 10MHz Sine Wave

Output

+5dBm, +/-3dBm 10MHz output output from isolated

distribution amplifier, driven by

on-board OCXO

U17 USB USB command and

control

USB 2.0 USB interface for SCPI and NMEA

sentences. Runs in paralell to TTL

serial port. Auto-switchover between

TTL and USB ports.

J3 1PPS output 1PPS output signal,

aligned to UTC

3.3V LVCMOS, <5ns rise-time.

10 Ohms output impedance,

can drive 50 Ohms

end-terminated cables

1PPS output signal, rising-edge

aligned to UTC when locked to GPS

Mini-JLT GNSS™ User Manual

The SCPI and NMEA outputs are sent to both the TTL serial output and the USB output, and the

SCPI control commands can be sent to either the TTL serial port, or the USB serial input, both

signals are “ored” together on the board. Commands can thus be sent to the board via both ports, but

should not be sent to the TTL serial port and the USB serial port simultaneously, as this will result in

non-destructive garbling of the serial transmission.

Connect an active or passive GNSS antenna that is compatible to 3.3V or 5V antenna power, 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, the 1PPS connector, and the 10MHz connectors on the Mini-JLT™

board are generic SMA types.

2.2 Power

The unit is powered from a +4.0V to +6V DC source, with +5.0V nominal voltage. The current is

typically less than 0.6A at 5V. Connect a clean +5V power supply to pin 6 of J1, and ground to pin 4

of J1. Both USB power and external +5V power can be connected at the same time to the unit, but

USB power will not be used to drive circuits on the PCB.

2.3 Multi-GNSS Capabilities

The Mini-JLT GNSS™ is capable of simultaneously receiving multiple 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 can increase

immunity against jamming which often occurs at only one 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 Mini-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 3.3.29 . 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.

Also, the internal GNSS receiver is restricted to operation at two different carrier frequencies. GPS,

SBAS, QZSS and Galileo operate at the same L1/E1 carrier frequency. GLONASS operates at a

separate G1 carrier frequency and BeiDou separately at the B1 carrier frequency. Based on this

restriction below are several valid combinations of GNSS systems that can be selected:

GPS, SBAS, GLONASS

Mini-JLT™ User Manual

GPS, SBAS, BeiDou

GPS, SBAS, Galileo, GLONASS

BeiDou, GLONASS

However, the following is an example of a combination of GNSS systems that would require three

different carriers and is not supported:

GPS, SBAS, BeiDou, GLONASS

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.

2.4 Connecting the GNSS Antenna

Connect the GNSS antenna to the SMA connector J4. Caution: use a Lightning Arrestor on your

Antenna setup. Use an amplified GPS antenna that is 5V LNA compatible. The Mini-JLT GNSS™

GNSS receiver is a 72 channel high-sensitivity multi-GNSS receiver with very fast lock time.

The Mini-JLT GNSS™ unit is set at the factory 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 mobile mode using the GPS:TMODE OFF command when the unit is to

be used in a mobile 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 frequency-lock the 10MHz output of the Mini-JLT GNSS™ GPSDO 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 TTL or USB serial port at 115200 baud, 8N1. Other Baud Rates can be

set via SCPI commands.

Attach the Mini-JLT GNSS™ unit to your PC’s Hyperterminal, the Jackson Labs GPSCon software

package (see Chapter 5 of this manual), or a third-party freeware Windows-based application

program called Z38xx. The Z38xx program can be used to track the performance of the Mini-JLT™.

Z38xx is available on the Jackson Labs Technologies, Inc. website under the following URL:

http://www.jackson-labs.com/assets/uploads/main/Z38XX.zip

2.6 Loop parameter adjustment

All loop parameters can be controlled via either of the two serial ports.

Mini-JLT GNSS™ User Manual

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

result in the unit’s performance to deteriorate.

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.

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 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, 25 being the default. Setting this value too high may cause loop instability.

A well-compensated unit will show performance similar to the plot shown in Figure 2.3 when

experiencing small perturbations:

Mini-JLT™ User Manual

Figure 2.3 Mini-JLT GNSS™ phase compensation plot

Mini-JLT GNSS™ User Manual

SCPI-Control Quick

Start Instructions

3.1 Introduction

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

TTL or USB serial interfaces 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 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 SCPI Commands

3.2.1 Quick Start Commands

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

help?

syst:stat?

gps?

sync?

meas?

3.2.2 *IDN?

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

Mini-JLT GNSS™ User Manual

3.2.3 HELP?

This query returns a list of the commands available for the Mini-JLT GNSS™ GPSDO.

3.3 GPS Subsystem

Note: Please note that Mini-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: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> [0,7]

GPS:DYNAMic 8 (Automatic Dynamic Mode)

GPS:DYNAMic?

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

GPS:REFerence:PULse:SAWtooth?

GPS:RESET ONCE

GPS:TMODE <ON|OFF|RSTSURV>

GPS:SURVey ONCE

GPS:SURVey:DURation <sec>

GPS:SURVey:VARIANCE <mm2>

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

GPS:SURVEY:STATus:DURation?

GPS:SURVEY:STATUS?

GPS:INITial:DATE <yyyy,mm,dd>

Mini-JLT GNSS™ User Manual

GPS:INITial:TIME <hour,min,sec>

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

GPS:JAMlevel?

GPS:FWver?

GPS?

3.3.1 GPS:SATellite

This group of commands describe the satellite constellation.

3.3.2 GPS:SATellite:TRAcking:COUNt?

This query returns the number of satellites being tracked.

3.3.3 GPS:SATellite:VISible:COUNt?

This query returns the number of satellites (PRN) that the almanac predicts should be visible, given

date, time, and position.

3.3.4 NMEA Support

The following four commands allow the Mini-JLT GNSS™ GPSDO to be used as an industry

standard navigation GNSS receiver. The GPGGA,GPRMC, GPGSV, PASHR and GPZDA NMEA

commands comprise all necessary information about the antenna position, height, velocity, direction,

satellite info, fix info, time, date and other information that can be used by standard navigation

applications via the Mini-JLT GNSS™ serial interfaces.

Once enabled, Mini-JLT GNSS™ will send 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.) regardless of the GNSS systems

enabled. Also, the GPGSV output uses a modified satellite numbering scheme as detailed in Section

3.3.8 to allow all different GNSS system satellites to be differentiated.

Please note that the position, direction, and speed data is delayed by one second from when the GPS

receiver internally reported these to the Mini-JLT GNSS™ Microprocessor, so the position is valid

for the 1PPS pulse previous to the last 1PPS pulse at the time the data is sent (one second delay). The

time and date are properly output with correct UTC synchronization to the 1PPS pulse immediately

prior to the data being sent.

Once set, the following two commands will be stored in NV memory, and generate output

information even after power to the unit has been cycled.

Mini-JLT GNSS™ User Manual

3.3.5 GPS:GPGGA

This command instructs the Mini-JLT GNSS™ to send the NMEA standard string $GPGGA every N

seconds, with N in the interval [0,255]. The command is disabled until the GNSS receiver achieves a

first fix.

This command has the following format:

GPS:GPGGA <int> [0,255]

GPGGA 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, 35m or more

are common.

3.3.6 GPS:GGASTat

This command instructs the Mini-JLT GNSS™ to send a modified version of the NMEA standard

string $GPGGA every N seconds, with N in the interval [0,255]. The command is disabled until the

GNSS receiver achieves a first fix.

This command has the following format:

GPS:GGASTat <int> [0,255]

This command replaces the regular NMEA GGA validity flag with a decimal number indicating the

lock-state of the unit. Please see section SERVo:TRACe for a 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, 35m or more

are common.

3.3.7 GPS:GPRMC

This command instructs the Mini-JLT GNSS™ to send the NMEA standard string $GPRMC every N

seconds, with N in the interval [0,255]. The command is disabled until the GNSS receiver achieves a

first fix.

This command has the following format:

GPS:GPRMC <int> [0,255]

3.3.8 GPS:GPGSV

This command instructs the Mini-JLT GNSS™ to send the NMEA standard string $GPGSV every N

seconds,

with N in the interval [0,255]. The command is disabled until the GPS receiver achieves a first fix.

GPS:GPGSV <int> [0,255]

Please note that due to the large number of GNSS satellites that can be tracked in this unit, more than

the customary four GSV messages can be sent once per second. With multiple GNSS systems

enabled, a typical sky view may generate up to six GSV messages per second.

Jackson Labs Mini-JLT GNSS User manual

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