[ntp:questions] GPS clock for Linux

Brian Utterback brian.utterback at sun.com
Mon Sep 15 14:31:54 UTC 2008

Richard B. Gilbert wrote:
> Terje Mathisen wrote:
>> Using a USB port for the +5V line is the canonical solution: Very 
>> cheap, dependable, and no extra wall warts.
>> Terje
> I have read claims here that the high and unpredictable latencies in USB 
> render it useless for time keeping!

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.

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.

Brian Utterback

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