Additional pps-gpio

[Achim Gratz]

Achim Gratz via devel writes:
> I've ordered a bunch of RS232 converters and USB UART today along wth
> another rasPi 3B and Tinkerboard, so I should be able to tell how much
> better things get exactly when you use line disciplining on a virtual or
> real serial port on these and also a PC soon.  Let's hope the FTDI chips
> are not fake on those USB UART so I get a full virtual serial with all
> modem control lines.

The FTDI boards are here and they work as advertised.  I have to solder
in the optional header strips in to get at the modem control lines
reliably, but just using a press-fit (sort-of) works OK for now.  PPS
line discipline via USB virtual serial works and produces the expected
~1ms offsets due to the USB poll interval.  It should be possible to
remove that shift by doing a loopback measurement via RTS/CTS
eventually.  Jitter is roughly on par with the local stratum-1 over
network.


Regards,
Achim.
-- 
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