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I saw guides for how to do it with the pi5, but I couldn't get it to lock to the pps reliably and chrony said I had way more jitter on pps and nmea than there should've been. Might try following this one minus the difference in pps

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are you trying to use gpio for the pps? feeding the pps into the NIC clock is what gets you the great accuracy, doing it with gpio on the main processor will have much worse jitter

PPS into GPIO will get you sub-millisecond error levels - you've got interrupts, after all!

Sub-millisecond jitter isn't perfect, but it should lock quite happily, you can get a lock on time sources with orders of magnitude more jitter.

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