[time-nuts] Re: GPSDO/GNSSDO project: STM32G4 + u-blox ZED-F9T + TDC7200

[Dan Kemppainen]

Hi,

I think we've seen what you are talking about, at least on different 
models.

What we saw working on a GPSDO was a 10.24nS wrap error, where the sign 
of the saw tooth correction shows up wrong. These were with the LEA-6T 
and M8 series modules. The solution was to check any 10.24nS correction 
values, and look for a ~20nS step change in corrected PPS compared to 
the OCXO. If changing the sign on the correction made more sense, run 
with the changed value.

Seems like with everything set up correctly, this happened about once a 
week to once a month. However that was over half a dozen years ago, and 
I'm going by memory.

How often are you seeing them?

Dan



On 8/15/2022 5:13 PM, time-nuts-request at lists.febo.com wrote:
> Subject:
> [time-nuts] Re: GPSDO/GNSSDO project: STM32G4 + u-blox ZED-F9T + TDC7200
> From:
> Marek Doršic <marek.dorsic at gmail.com>
> Date:
> 8/15/2022, 5:06 PM
> 
> To:
> Discussion of precise time and frequency measurement 
> <time-nuts at lists.febo.com>
> 
> 
> Hi,
> 
> I also see these "odd uncorrected wrap" of timepulse ofset reported by TIM-TP messages with TIM-2.21 firmware.
> 
> What is the best way to correct for these? I add/substract 7.8125 ns, being one cycle of the internal clock at 128 MHz.
> Never found a reliable source stating the clock is running at 128 MHz.
> 
>     .md
>