Thunderbolt GPS clock

[_Zephyr_]

Hi everyone,

I am a USRP novice. I am working on connecting several USRP devices together with the external clock (building a MIMO system).

My USRP is NI 2921 and the external clock is Thunderbolt GPS clock which is recommended in the article:

http://www.ni.com/white-paper/14311/en

Unfortunately, with the default setting, the PPS output is disabled. To activate this output, I connect the Thunderbolt clock to my computer with a COM cable and run official management software "Thunderbolt Monitor". Following picture shows what I got: all fields are filled with question marks. Also, I found that the TX in the lower left of the status bar always blinks while the Rx

keeps dark. This indicates that the software keep transmitting commands to the clock, but does not receive any feedback reports from the clock.  

Is there anyone who has similar issues? Is there any suggestions about my case?

Thanks a lot

[m0mik]

Hi,

You could try the Lady Heather GPSDO Control Software from the following URL:

http://www.ke5fx.com/heather/readme.htm

What is the make and model of your Thunderbolt GPS?  I'd recommend looking through the manual to check the default baud rate is correct.  Also make sure you are using the correct com port in device manager.

Regards,

Mike

--
Mike Jameson M0MIK BSc MIET
Email: mike@scanoo.com
Web: http://scanoo.com

[AlejandroZepeda]

Hi.

From the image you posted, it looks like the SW is configured for no parity, but I think the default is odd parity.  You can go to Setup menu >> Serial Configuration and change the serial port settings.  You might have to try many different settings to find the one that matches your device.  Trimble also has a newer software called Trimble GPS Studio, which also supports the Thunderbolt.  That SW has a feature to automatically try all the serial settings it supports until it finds the one that works with the device it is connected to.  I have never tried to see how well that feature works, but it may be worth for you to try.

http://trl.trimble.com/dscgi/ds.py/Get/File-484972/TrimbleStudio.exe

Hope this helps.  Good luck!

Alejandro

[_Zephyr_]

Hi, Mike

Thanks a lot for your suggestions.

My GPS model is "Thunderbolt PRECISION GPS 10mhz FREQUENCY&TIME Standard", which is a second-hand one and purchased from Ebay. I have tried the software from the suggested link. But it seems that the connection between my computer and the GPS clock still fails to be built. The software shows "No COM1 serial port data seen". I believe that I have used right serial port (COM1, only one in my computer) and configured right baud rate according to the requirement of the device user guide manual.

Also, I use Trimble GPS studio which can automatically try all possible serial port configurations to build the connection. The result is that none of these configurations successfully communicate with my GPS clock.

I wonder if the serial port at my GPS clock is out of work. Do you have any further suggestion about my case? Is there any way to check the serial port of the clock?

Regards,

Colin 

[_Zephyr_]

Hi, Alejandro

Thank you very much for your suggestion.

According to the user manual of the clock, the default parity is none.  Also, I use Trimble GPS studio and make it automatically try all possible serial port configurations to build the connection between my computer and the clock. However, the result is that none of these configurations successfully communicate with my GPS clock.

I wonder if the serial port at my GPS clock is out of work. Do you have any further suggestion about my case? Is there any way to check the serial port of the clock?

Regards,

Colin 

[AlejandroZepeda]

Hi.

If none of the settings work, then maybe the serial cable is the wrong type.  Maybe you need a null-modem cable and you have a straight-through cable, or the other way around.  Another thing to try, if you have a scope, is to probe pins 2 and 3 of the DB-9 connector on the Thunderbolt.  One of those 2 pins should be its TX pin and you should see it toggling at RS-232 voltage levels (over +3V and under -3V); the other pin is the RX.  Once you find the TX pin you should be able to look at the signal and figure out the baud rate and parity settings to ensure the computer port is configured correctly.  You can then also connect the cable and probe at the other end of the cable to ensure the cable is working properly, and to determine the type of cable you have (null-modem or straight-through).  Then you can also probe the computer's port to see on which pin it is transmitting, and determine if they are both trying to transmit on the same pin.  If so, you know you need to get a different kind of cable.

Good luck.

Alejandro