[time-nuts] Re: The STM32 GPSDO, a short presentation

[Erik Kaashoek]

Hi Carsten
I'm indeed using a similar setup where a TCXO is used as HE clock.
The PPS triggers a 32 bit capture and the SW PLL controls the Vtune of 
the TCXO
The PPS is generated using another timer which gives me the possibility 
to either output a PPS or 10MHz
I'm using a TCXO because of cost,  power consumption and size reasons 
and the performance is good enough for my application.
An OCXO would for sure perform better.
Erik.

On 14-4-2022 23:44, Carsten Andrich wrote:
> Hello Erik,
>
> could you elaborate on your setup? Which oscillator (OCXO?) are you 
> using to drive the STM32's PLL?
>
> I'm currently toying around with a (presumarly?) similar 
> configuration. An RCB-F9T's 1PPS fed into an STM32G4's 32-bit timer 
> capture to reference the 1PPS to a local oscillator with ~6 ns 
> resolution, subsequently generating a stabilized 1PPS using another 
> output channel of the same timer. The STM32's PLL is still using a 
> cheap chrystal, but I'm currently working on replacing that with an OCXO.
>
> Best regards,
> Carsten
>
> On 01.04.22 18:19, erik at kaashoek.com (Erik Kaashoek) wrote:
>> Nice, I'm trying to do something similar. But without the PICdiv or the
>> TIC measurement. Only the GPS PPS into the STM32 and the stabilized PPS
>> is generated by a timer in the STM32
>> First step was to measure against the running average of the GPS PPS.
>> As can be seen in attached Timeplot measurement the phase error is (when
>> temperatures stabilized) in the order of 10ns.
>> Erik.
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