[ntp:questions] GPS clock for Linux

Chris Adams cmadams at hiwaay.net
Mon Sep 15 18:34:49 UTC 2008

Once upon a time, Brian Utterback  <brian.utterback at sun.com> said:
>So, apparently not entirely useless. Using USB as a power source is 
>getting to be highly popular. Witness the number of cup warmers, fan, 
>etc. on the market. As long as you don't try to read the signal via 
>USB, it should be okay.

Another power source solution (especially for those like me that don't
have an open RS232 port anyway) is the SIIG series of PCI/PCI-E RS232
cards; they can optionally provide +5V or +12V on a pin.

>One thought occurs to me. Would it work to have the PPS signal go to a 
>serial port but the actual NMEA sentences be read via USB? It seems to 
>me if the total jitter of the USB still kept the snetences timing 
>within half a second it would work.

I am actually doing that right now (using the parallel port instead of
the serial port in my case); it works fine.

Has anyone tried isochronous mode USB to see if that helps with the
latency?  I have an FTDI USB-to-RS232 interface that supports
isochronous mode, but I haven't had a chance to try it.

Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

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