[time-nuts] Linux PPS clues?

bownes bownes at gmail.com
Fri Nov 4 23:34:20 EDT 2016

I suspect the multitasking aspect of the OS will give you far more jitter than one could cope with. 

> On Nov 4, 2016, at 22:46, Casey L. Jones <timenuts at caseyljones.com> wrote:
> Maybe you could use something like a serial to parallel converter chip or the serial port input of a microcontroller. You could feed in a constant string of zeros until an event, and then feed in a one to the stream when the event occurs. You could save the stream of ones and zeros in memory for maybe a second, and then stamp the block with the time. Then you can have your main CPU figure out the time of each event by knowing the bitrate and looking at how many bits precede each one bit back to the beginning of the block. The blocks would likely be largely zeros, and would thus compress really well if you decide to not even bother converting the format of the blocks to a timestamp format. The advantage of this scheme is that it could probably have a sampling rate far higher than a timestamping process, without overstressing even many modestly powered processors.
> Another way to synchronize your samples with GPS, at the cost of some sample rate, is to use a two input multiplexer at your serial input and to take every odd bit of your serial stream to be a sample of the pps output of your GPS and every even bit to be the state of your event trigger. That way your pps and data are interleaved in your bitstream for post processing.
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