SAFRAN GDK-2 Designer Kit

Product Information

Specifications

• Product Name: GNSS/SRo-100 GDK-2 Designer Kit
• Resolution: Auto-Adaptive 1 ns
• Revision: 270824
• Date: 27 August 2024

Product Usage Instructions

Board Description
Provide an overview of the components and layout of the board.

Introduction
Explain the purpose and key features of the GNSS/SRo-100 GDK-2 Designer Kit.

Supported GNSS Receivers
List the compatible GNSS receivers that can be used with the kit.

System Requirements
Outline the necessary system requirements for optimal performance.

Installation Procedure
Step-by-step guide on how to install the kit, including safety precautions and environmental considerations.

Standalone SRO Master Oscillator
Instructions on using the standalone SRO master oscillator feature.

GNSS-Disciplined SRO Timing Clock
Introduction to the GNSS-disciplined SRO timing clock and setup instructions.

External PPS Disciplined SRO Timing Clock
Setup guide for the external PPS disciplined SRO timing clock.

Tracking Mode
Explanation of the tracking mode feature and how to use it.

PPS OUT Delay
Instructions on setting the PPS OUT delay.

Module Customization
Details on how to customize modules, user-defined messages, and GNSS command settings at startup.

FAQ

• Q: How do I reset the kit to factory settings?
  A: To reset the kit to factory settings, follow these steps: [Provide detailed instructions on resetting the kit]
• Q: What should I do if I encounter connectivity issues with the GNSS receiver?
  A: If you experience connectivity problems with the GNSS receiver, try the following troubleshooting steps: [Provide troubleshooting tips for connectivity issues]

Board Description

Tag	Description	Tag	Description
B1	10 MHz output, rear.	C1	External frequency adjust. FA: connected to pin 6 of the SRO. Vref out: connected to pin 7. GND: ground. In association with switch S2.
B2	PPS output, rear.	C2	Power supply. GND: ground. V+: 12 Volt or 24 Volt.
B3	PPS Ref output (GNSS), rear.	C3	Second power supply (do not use with SRO)
B4	60 MHz output.	C4	Serial RS232 interface.
B5	PPS Ref input.	C5	PPS Ref input. Power supply. Same as C2. For jack plug in.
B6	10MHz output, front.	C6	Connector for SRO.
B7	PPS output, front.	C7	GNSS interface.
B8	DDS output.	P1	Potentiometer for frequency tuning. In association with switch S2.
S1	Working mode selector. Pos.1: free run. Pos. 2: Sync. Pos.3: Track.	L1	Green Led, power supply ok.
S2	External frequency adjust source. Left: potentiometer P1. Right: external, connector C1. Default: Right.	L2	Green Led, tracking good.
S3	GNSS antenna voltage selector. Left: +3.3V. Right: +5V.	L3	Red Led, Rubidium line not locked.
S4	PPS reference selector. Right: on board GNSS receiver, if any. Left: External, B5.	L4	Green Led, PPS Ref tick.
S5	Reset switch
S6	GNSS mode selector Left: 1 way Right: 2 ways

Introduction

The designer kit allows users to rapidly interface an SRO with a GNSS receiver or an external 1PPS reference. Through the RS232 serial interface, the user can communicate both with the SRO and supported GNSS receivers. The designer kit is ideally suited for developing a suite of timing applications based on the GNSS time distribution system.

Designer Kit Serial Interface Diagram

The PC listens to the SRO and the GNSS. The GNSS listens to the PC and SRO, but the SRO just listens to the PC.
In this situation, Switch S6 to the left, the PC can communicate with both the GNSS and the SRO. Communication with the SRO only: Switch S6 to the right. Communication with the GNSS only: Take SRO away and Switch S6 to the left.

Supported GNSS Receivers
Currently, 2019, only the u-Blox LEA-xT is supported. Regarding the Antenna, see App Note “GPS Antenna Installation Guidelines & Specs.”

System Requirements

• A PC with:
  • Any Windows from XP to 10
  • A free serial port (RS232, 9 pin Sub-D)
  • An SRO-100
• A 24V/2A or 12V/3A properly filtered power supply and power cable with 2 wires of different colors.
• A serial cable with 9 pin Sub-D connectors. One connector male, the other female.
  • Pin 2 connected to pin 2.
  • Pin 3 connected to pin 3.
  • Pin 5 connected to pin 5.

Installation Procedure

Safety!

• Warning: Use proper ESD precautions
• Caution: Ensure that all cables are properly connected

Handling the product in reasonably foreseeable conditions do not cause any risk for human health, exposure to the SVHC (substances of very high concern) would require grinding the component up.

Environmental Responsibility

• The equipment contains materials, which can be either re-used or recycled.
• Do not deposit the equipment as unsorted municipal waste. Leave it at an authorized local WEEE collection point or return to Safran to ensure proper disposal.
• To return the appliance:
  • Submit a support ticket at aftersales.clocks@nav-timing.safrangroup.com and request an RMA.
  • We will contact you for more information and/or with shipment process details.

System Installation

• Connect the serial cable from the evaluation board to the PC.(C4)
• Mount an SRO on the evaluation board.(C6)
• Connect the evaluation board to the power supply.(C2)
• Connect the negative pole to “GND” and the positive pole to “+12”.
• !!! Be careful. The Evaluation Board is not protected against polarity inversion.
• After 1s, the red LED on the Evaluation Board should light ON.(L3)
• That means the SRO is warming up.
• After maximum 10 minutes, the red LED should turn off, indicating the SRO is now centered on the Rb line.
• Put the CD Rom inside the reader.
• With Explorer, start the program iSyncMgr.exe.
• By default, the serial port is COM1.

If a warning popup window appears before the program iSyncMgr starts, it means COM1 is not free and another port has to be chosen. To do that, go to “Serial Port \ Port No” menu. Then choose another port.
Once the serial port problems are fixed, the button “Refresh” can be clicked. The Identification, Serial Number and Status of the SRO connected to the Evaluation Board should appear.

Now the Designer Kit is installed and is working properly. For easy communication, the iSyncMgr.exe application can be installed onto the user PC. This simple program is distributed freely. It doesn’t write any code in the base register. It is recommended to check/download the last version of this software at https://safran-navigation-timing.com/.

Standalone SRO Master Oscillator

iSyncMgr Setup

• Click the Button “Refresh” from the main window.
• The Status should be 4 (Free Run).
• If not, go to the “Timing + Tracking” menu and choose “TRx”.
• In the “Track and Sync” dialog box, click the button “Don’t track”.
•  If there was an “X” on the left of the button “Track after Reset or Power On”, it should disappear.
• If the “X” remains, it means the switch (S1) on the designer kit is on 2 or 3. Put the switch (S1) on 1. The “X” should be gone.
• Leave the dialog box “Track and Sync” and click again on “Refresh”. Now the Status should be 4 (Free Run.)

Hardware Frequency Adjustment
In the SRO, the center frequency of the Rb line can be adjusted by changing the c field. With the designer kit, there are 3 ways to do that:

1. By applying a tension from 0 to 5 volts between “GND” and “FA” .(C1)
2. By connecting a potentiometer between “GND” and “Vrefout”.(C1) The middle point of the potentiometer should be connected to “FA”.
3. By activating the on-board potentiometer (P1) with the switch (S2); to the left.

In the 3 cases, the nominal frequency of the SRO will be modified. When not forced to another potential, the tension of “FA” is approximately 2.5 Volts.

Note: The SRO is factory tuned to 10.000’000’000 MHz. (Reference: GNSS). This tuning is only correct if pin 6 is let free, and not forced to a voltage.

Software Frequency Adjustment
In case of a high-resolution frequency counter style HP, referenced by another 10 MHz master:

• Connect the “RF out” of the Evaluation Board to the counter. Make sure the counter is averaging to have enough digits. (at least 10 to 11 digits).
• From iSyncMgr, go to the “Timing + Tracking” menu and choose “FCsddddd”.
• For the correction, there is a simple rule:
• Take the value to be corrected in mHz (milliHertz) from the counter.
• Multiply by 100.
• Then subtract this value to the value in E-12 as read in the “Frequency correction” dialog box.
• Type the new value in the “E-12” field.
• Click on the buttons “<=Compute” and then “Store”:

The new frequency is now stored in the EEPROM of the SRO and, if the calculations were correct, the counter should indicate a value close to 10 MHz, tile the last mHz digit. (+/-1 digit)

PPSREF Frequency Comparison
In the case of a master sending out a PPS Ref:

• Connect this PPS Ref to the connector (B5) of the Evaluation Board.
• From iSyncMgr, go to the “Timing + Tracking” menu and choose “BTx”.
• In the Dialog Box “Beat something”, click on the “PPSINT vs PPSREF” button.
• The field below gives out the phase in 133 ns steps, between PPSINT and PPSREF.
• With the relationship: , we can find out the frequency difference between the two clocks.
  Example:

Other schemes to measure the frequency difference can be set up. The phase evolution can be recorded for further computations with the “Stable32” application per example. To do this in the Dialog Box “Beat Signal”, click on the “Record” button. From now, the data coming out from the SRO are appended to the file “srolog.txt” as long as the Dialog Box is opened. For simplicity, srolog.txt is located in the same directory as iSyncMgr.exe is on a CD Rom, no writing is done.

GNSS-Disciplined SRO Timing Clock

Introduction
The SRO is equipped with standard software able to track any PPS input reference signal with an auto adaptive filtering. (Please refer to the article wp_sro.pdf at [SAFRAN WEBSITE?]).
With this designer kit it is possible to validate a proven GNSS Disciplined (Rb) Oscillator configuration.

Setup

• Put a GNSS receiver on (C7).
• Choose GNSS as PPS Ref source by putting the switch (S4) to the right.
• The tracking can be initialized with the slide switch (S1). Position 1 or 2.
• It can also be initialized with iSyncMgr. To do so, go to the “Timing + Tracking” menu and choose “TRx”. Then click on the “Track now” button.
• If the SRO has to go immediately in tracking after Power ON and Warming Up, click on the button “Track after Reset or Power On”.
• After the tracking is set up, it takes a few minutes before the tracking becomes effective.

External PPS Disciplined SRO Timing Clock
The Evaluation board has a connector for an external PPS Ref.(B5)

•  Setup
  • Connect the PPS Ref to track to the (B5) BNC connector of the Evaluation Board.
  • To make the connector active, move the switch (S4) to the left.
  • Then the procedure is the same as for the tracking of a GNSS PPS Ref., see Chap. 7.2

Tracking Mode

Tracking Mode Check
If the tracking to a PPSREF is successful, the green LED (L2) on the Evaluation Board will be lit.

• With iSyncMgr, it is possible to follow the evolution of the tracking. To do that, go to the “Timing + Tracking” menu and choose “ST”.
• As long as the tracking is set up, the Status is 1.
• Finally, the Status comes 2, “Track to PPSREF”.
• The evolution of the tracking can also be followed more numerically. For that, go to the “Timing + Tracking” menu and choose “BTx”
• Clicking the button “PPSINT vs PPSREF” gives out the phase difference between the 2 PPS in 133 ns steps.
• Clicking on the button “Phase comparator” gives out the phase difference between the 2 PPS in approx. 1 ns steps. Please note that this value does not have any precision. It is just used to increase the resolution of the tracking loop.
• Clicking on the button “ PPSINT vs PPSREF + Phase comp.” gives out both values.
• As described before, see Figure 5: Dialog Box “Beat Signal” Setup, these values can be continuously recorded by clicking on the button “Record”. The data coming out from the SRO are append to the file srolog.txt
• To see the frequency that the SRO is actually using to track a PPSREF, go to the “Timing + Tracking” menu and choose “FCsddddd”
• Each time the button “Read” is clicked, the frequency in use comes out.

Loop Time Constant Tracking
There are two working modes as follows:

• The tracking loop time constant can be set automatically by the SRO itself after analyzing the stability of the PPSREF, or it can be set by the user.
• Factory setting is the automatic mode. In this mode, the time constant can vary from 1000 s to 100’000 s.
• But the user can force a time constant from 1000 s to 999’999 s.
• To check the time constant mode in use, from iSyncMgr, go to the “Timing + Tracking” menu and choose “TCdddddd”. The “Tracking loop time constant” dialog box gives out a value.
• If the value is 000000, it means the SRO is in automatic mode.
• A value between 1000 and 999999 means the time constant was forced by the user.

Normally the tracking loop time constant should be left in automatic mode. But it can be useful to put it to 1000 s to force the SRO to reach quickly the frequency of a master oscillator. Don’t forget to put it back to automatic mode after it is done.
It is possible to check the stability of the PPS ref with the command VS and the time constant in use with the command VT. This is only possible in tracking, status 2 or 3. Please note that the value coming out with VS is averaged during hours.

Frequency Saving
When the SRO is tracking a PPSREF, the average frequency is saved every 24 hours in EEPROM. So, in case the SRO is powered off, it will restart with the right frequency.

But this way of working can be changed.

• From iSyncMgr, go to the “Timing + Tracking” menu and choose “FSx”. The “Frequency save mode” dialog box pops up. Normally a “X” should appear at the left of the button “Save average frequency in EEPROM every 24 hours”. That means the average value of the frequency is saved in EEPROM every 24 hours. But only if the tracking is successful. To avoid this saving, click on the button “Don’t”.
• By clicking the button “Save integral part of freq. now”, the saving of that value is made.
• By clicking the button “Save actual frequency now”, it is not the integral part of the frequency that is saved, but the actual value.

Phase Deviations
A regulation loop tries to reduce the error between a local input parameter and an external reference by changing an output parameter.
In the SRO, the error is the phase difference between PPSINT and PPSREF. The output parameter is the frequency. As the frequency should be as stable as possible, some input error is allowed.
The question is: What input error is acceptable? In the SRO, the answer was split in two: If the phase error goes out a first window, an alarm is raised up. In case the phase error goes out a second window, the tracking is stopped. It is so, as the SRO is supposed to track a Master at least as stable at itself. To adjust these two windows from iSyncMgr, go to the “Timing + Tracking” menu and choose “TWddd”. The “Tracking and Alarm Window” dialog box pops up.

PPS Ref Stability Requirement before Going in Tracking Mode

• The indication given here are only available for SW Vers. 1.09.
• Frequency offset between the master and the SRO:
• No test is done. To change this behavior, please contact our support department.
• PPS granularity of the master:
• A granularity of ±133 ns is acceptable.

Frequency Jump when Going in Tracking

• The indication given here are only available for SW Vers. 1.09.
• The SRO doesn’t make an initial frequency adjustment before going in tracking. To change this behavior, please contact our support department.

Tracking Restart

• The indication given here are only available for SW Vers. 1.09.
• The SRO is not able to restart a stacking tracking. To change this behavior, please contact our support department.
• ! This mean all precautions should be taken to avoid that the SRO receives a PPS Reference from a GNSS with no satellites in view during the tracking initialization.

PPS OUT Delay

Free Run Mode
It is possible to make some experiments with a PPSREF and a scope.

• Connect the PPSREF to the scope trigger and the PPS OUT of the Evaluation Board to a scope channel.
• Reset the SRO until the PPSOUT pulse of the SRO is visible with a time sweep not too slow.
• From iSyncMgr, go to the “Timing + Tracking” menu and choose “DEddddddd”.
• Show on the scope how the PPS OUT pulse is moving when the delay is changed.
• In Free Run, the delay is referenced to itself.

Tracking Mode

• Connect the PPSREF to the Evaluation Board too. (B5)
• And set up a tracking. (TRx / “Track now”)
• Now, go to see what happens in the “PPSOUT delay and width” pop up dialog box. (DEddddddd).
• The delay is 9999999 steps. It means that, during the tracking set-up, the delay is not defined and it cannot be changed.
• Wait until the Status comes 2 and check again the “PPSOUT delay and width” pop up dialog box. Now the delay is something between 0000000 and 7499999, and it can be changed.
• In Tracking, the delay is referenced to PPS REF when the tracking is perfect.

Sync Mode
In sync mode the SRO don’t just try to adjust it’s frequency to the one of a master. But it also aligns its PPSOUT to the PPSREF of the master. Let’s make a small experiment.

• Connect the PPSREF to the scope Trigger and to the Evaluation Board.
• Connect the PPS OUT of the Evaluation Board to a scope channel.
• Be sure the SRO is not set in Track or Sync mode by hard or by soft.
• Reset the SRO until the PPSOUT pulse of the SRO is visible with a time sweep not too slow.
• Remember the position of the PPS OUT pulse on the scope.
• Now , set up a tracking, with the switch (S1 position 3) on the Evaluation Board and wait until the green LED lights on.
• Observe that the PPS OUT pulse don’t move. Now put the switch to Sync (S1 position 2).
• Immediately the PPS OUT pulse jumps to the left side of the scope screen, because the PPSOUT of the SRO is now aligned to the PPSREF.

Module Customization

The SRO can be customized. For that, go to “Timing + Tracking” and then click on “MCsdd”.

User Defined Message
The message $00 is the identification of the SRO. It can be turned off and replaced by a user message stored in EEPROM, the message $01.

GNSS Command Settings at Startup
The GNSS receiver is the u-Blox LEA-xT. In this receiver, the configuration is stored in eeprom and doesn’t need a configuration at startup.

Updating the Firmware

With iSyncMgr.exe, it is possible to update the SRO to the last software revision.

Choose Update. The program will check the SRO. If the Update is possible, the STATUS on the dialog box will be “Update possible”. Then click on “Update 1.xx”.
WARNING: The process takes approximately 1 minute. If for any reason, like power down or defective serial cable, the process is aborted, then the SRO shall be sent back to factory.

Supporting Documentation

• https://safran-navigation-timing.com/product/gdk-2-designer-kit/
• https://safran-navigation-timing.com/document/gnss-lea-xt-and-gdk-2/

Mechanical Specifications

Safran Technical Support
For technical support, you can visit https://safran-navigation-timing.com/support-hub/ to submit a support request.

For product specifications and additional documentation, visit our product page at https://safran-navigation-timing.com/product/gdk-2-designer-kit/

Information furnished by Safran is believed to be accurate and reliable. However, no responsibility is assumed by Safran for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Safran reserves the right to make changes without further notice to any products herein. Safran makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Safran assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. No license is granted by implication or otherwise under any patent or patent rights of Safran. Trademarks and registered trademarks are the property of their respective owners. Safran products are not intended for any application in which the failure of the Safran product could create a situation where personal injury or death may occur. Should Buyer purchase or use Safran products for any such unintended or unauthorized application, Buyer shall indemnify and hold Safran and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable legal fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Safran was negligent regarding the design or manufacture of the part.

Safran Electronics & Defense
safran-navigation-timing.com

Documents / Resources

SAFRAN GDK-2 Designer Kit [pdf] User Manual GNSS-SRo-100, GDK-2, GDK-2 Designer Kit, GDK-2, Designer Kit, Kit

References

• User Manual