[time-nuts] Raspberry Pi NTP server

[Petr Titěra]

Timing on USB need not to be so horrible. Below is stats from my server 
with GPS connected using FT232H chip (supporting high speed transfers on 
USB). Yes, the jitter is far greater than on other computer where PPS is 
connected directly but it is a lot less than that 500microseconds you 
get with common USB convertors.

      remote          refid     st t when poll reach delay offset jitter
=======================================================================
o127.127.22.0   .PPS.           0 u    7   16  377  0.000 -0.019  0.033
*192.168.3.240  .GPSD.          1 u   24   64  377  0.377  0.187  0.026
+192.168.3.246  .PPS.           1 u   28   64  377  0.643  0.181  0.028

Petr Titera

On 03.07.2020 19:44, Hal Murray wrote:
> 
> andrew.hancock at cyrus-consultants.co.uk said:
>> So I cannot use HaTs anymore, so I cobbled together a GPS ublox6 (same
>> module) but using a FT232RL, and connected all the pins correctly, and DCD so
>> I can get PPS.
> 
> FT232R is a USB chip.  Timing over USB is "interesting".  Do you know about
> hanging bridges?
> 
> Can you get a wire in to the GPIO pin the HAT used?  That would be an
> interesting experiment.
> 
> There may be a parameter you can tweak, but I can't think of the name right now.
>