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

[Erik Kaashoek]

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.

On 31-3-2022 12:52, André Balsa wrote:
> Hello fellow time-nuts,
>
> My second post to the list. I just wanted to mention that the STM32 GPSDO
> is a 100% Open Source project, fully documented in the GitHub repository
> https://github.com/AndrewBCN/STM32-GPSDO and the EEVblog thread
> https://www.eevblog.com/forum/projects/yet-another-diy-gpsdo-yes-another-one/
> . Also some details are available about the firmware in the stm32duino
> forum thread https://www.stm32duino.com/viewtopic.php?f=10&t=1031
>
> The project has some unique features compared to any other commercial or
> hobby GPSDO and it is still very much in full swing and actively developed
> not only by myself but also by a few collaborators.
>
> One of the unique features of the STM32 GPSDO is that it uses both a PLL
> and an FLL. I developed the 100% software FLL around May 2021 and for the
> PLL I have borrowed Lars Walenius genius TIC design with Erik Kaashoek's
> modifications (using a 74HC74 instead of a 74HC4046) (WIP). I am also using
> a picDIV by Tom Van Baak to generate a UTC synchronized PPS (again, WIP).
>
> The project can be assembled on a breadboard in one afternoon provided one
> has all the parts and it works "out of the box". The BOM total cost stands
> at around 45€ for the basic version and 70€ with all the bells and whistles.
>
> The firmware leverages the Arduino programming environment and the hundreds
> of available libraries, and it is written with the express purpose of being
> easy to understand, maintain and further develop. It now stands at around
> 1700 lines of C/C++ code with extensive comments.
>
> The main communications channel for this project is the EEVblog thread
> mentioned above.
>
> Greetings from France,
> Andrew
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