[time-nuts] Raspberry Pi NTP server

[Hal Murray]

stevesommarsntp at gmail.com said:
> My RPi4 (Raspbian Buster) has a GPS+PPS/USB.  Serial->USB uses Prolific
> PL2303, which supports USB 2.0 

> which means 1 msec polling of the PPS signal.   I've been unable to poll more
> frequently

As far as I know, the PL2303, 067b:2303, is an old/slow chip.  (I forget the 
right magic USB terms)  Why do you expect it to go faster than 1 ms?

It and the FTDI chip(s) are popular and widely known to be well supported on 
Linux.  I'll be very surprised if it goes faster.

What sort of device are you using?  One way to tell if it is likely to go 
faster than 1 ms is the thickness of the wire.  Faster speeds need more 
shielding for EMI reduction (or something like that) which turns into fatter 
cables.  It's pretty easy to tell if you have samples of both in front of you. 
 I think you can only use the thinner cable if t runs at 1 ms and you hard 
wire the chip to the end of the cable as is typical of a GPS mouse.



-- 
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