[time-nuts] Re: PRS-10 sawtooth correction with microcontroller

[Matthias Welwarsky]

On Donnerstag, 22. Dezember 2022 00:22:37 CET James Wilson via time-nuts 
wrote:
> After running in many of the familiar problems of connecting a GPS timing
> module 1PPS signal to a PRS-10, I want try building a software sawtooth
> correction board. I’ve seen previous discussion of some of the commands to
> use for adjusting the PLL and PPS control on the PRS-10 and getting the
> sawtooth error from ublox GNSS modules, but not a start-to-finish
> description of how to put everything together.
 
> My idea to use a microcontroller with multiple UART ports; one connected to
> the ublox module and the other connected to the PRS-10, with level shifters
> as needed. The microcontroller sits between the two devices, and gets the
> PPS sawtooth correction info from the ublox (specifically via the
> UBX-TIM-TP message and its qErr field), and then adjusts the PRS-10’s PPS
> time offset by this value to null out the sawtooth for the next pulse.

I suggest you try correcting the 1PPS pulse of the timing module itself, using 
a variable delay line. I don't have a particular part in mind, Maxim might 
have something.

There was a very elaborate GPSDO project discussed last year on this list that 
used this technique.

BR,
Matthias

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