[time-nuts] GPS module recommendation for Pi timing

[Thierry MUSEUX]

Hi,
For your application and 1 ms accuracy ,the problem,  this is a long time that i have made that, it is in the output and the information on a serial link or GPIO  on a no Real Time OS. Even if you don't want using USB in an  internal the PI use an USB serial port. There are some parameter in the USB driver to manage the answer.
 For the GPIO it is also  a driver to manage.

To have a good  accuracy the best way is to use RTOS or best a metal OS to manage the GPIO.
Or allow some slope accepted modular time.

Thierry M

-----Message d'origine-----
De : time-nuts [mailto:time-nuts-bounces at lists.febo.com] De la part de Brian Lloyd
Envoyé : vendredi 13 mars 2020 15:06
À : Discussion of precise time and frequency measurement
Objet : [time-nuts] GPS module recommendation for Pi timing

I have an application where I need to synchronize the internal TOD RTC in a
raspberry pi and need to pick a GPS module. We are building our own
hardware but still using the Pi so interconnection will be via GPIO/serial.
We won't try to use USB.

This is not an NTP application. These units will be in the field and will
most likely not have Internet access. I need their clocks to be pretty
close. I am shooting for 1ms ... if possible.

The new M9F and M9T modules from Ublox are a bit pricey. The M8T is a bit
more reasonable. OTOH I realize there are limits to how tightly I can
control the Pi's RTC and will run into diminishing returns, so even the M8T
might be overkill.

Has anyone here figured out what the reasonable limit is for timing on a
Pi, and what makes sense for a timing module for an application like this?

Thanks.

-- 



Brian Lloyd
706 Flightline
Spring Branch, TX 78070
brian at lloyd.aero
+1.210.802-8FLY (1.210.802-8359)
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