GSM clock GPS txco help

Will Hawkins hawkinsw at
Wed May 22 21:35:22 UTC 2013

Thanks Alexander,

I will give this a try first thing tomorrow morning and let you know how 
it goes!


On 05/22/2013 05:30 PM, Alexander Chemeris wrote:
> Hi Will,
> Thank you for the good news. Answering to your question, first please
> update your UmTRX firmware and host side UHD:
>   1. Update your UHD and umtrx_scripts from the git. Build UHD.
>   2. Flash attached ZPU firmware to a UmTRX with the following command:
>        ./ --addr= --fw=usrp2p_txrx_uhd.bin
>   3. Power cycle UmTRX
> Calibrate with GPS:
>   1. Take your UmTRX outside to get GPS lock.
>   2. When GPS acquires a lock, use '' utility without
> parameters to read current VCTCXO DAC value in a loop.
>   3. When the value stabilise (couple minutes after GPS acquires the
> lock), write this value to EEPROM:
>        ./usrp_burn_mb_eeprom --key tcxo-dac --val <YOUR_VAL>
>   4. Now i should pickup the value from EEPROM on boot, so GPS is no
> required unless you change ambient temperature considerably.
> Note, that you should warm up your UmTRX for a while before
> calibration, because it depends on the TCXO temperature.
> Let me know if something goes wrong - I wasn't able to test
> everything, as I don't have my UmTRX with me at the moment.
> On Tue, May 21, 2013 at 9:50 PM, Will Hawkins
> <hawkinsw at> wrote:
>> Hey Alexander!
>> Yesterday we took our umtrx outside to get the GPS lock for calibrating the
>> tcxo voltage. There were some good outcomes and bad outcomes:
>> The good:
>> If you remember correctly, Dan could not associate to the umtrx with his
>> Galaxy Nexus. After getting a GPS signal, Dan's phone could associate! So,
>> great news.
>> The bad:
>> We attempted to record the calibrated tcxo dac values and had no luck. We
>> booted the umtrx board connected via serial console to my laptop. I was able
>> to see the boot messages and other output so I know the console was working.
>> Once the board got a GPS lock, I assumed that I would see some tcxo DAC
>> values printed to the console. Based on what you said last week, I was going
>> to wait until those values stabilized and then use that output to flash into
>> the eeprom. Unfortunately I did not see any output on the serial console.
>> Then I thought that we could poll the umtrx (using UHD probe) for its tcxo
>> dac values. Unfortunately it showed the default (2048) every time.
>> Can you tell me what I'm doing wrong?
>> Thanks!
>> Will
>> PS: CC'ing Dan since he's working this with me.

More information about the UmTRX mailing list