[time-nuts] GPS clock to RT-Linux for pulsar machine

Matt Ettus boyscout at gmail.com
Fri Jul 1 17:06:05 EDT 2005

> Don't do it that way, you will get in trouble with the interrupt
> latency.

I have to echo this advice.  While RTLinux and other RTOS'es have
great interrupt latency performance, using those interrupts to trigger
sampling on an ADC is a bad idea.  It won't work at all if you are
trying to sample faster than about 1-10 kHz, and the jitter is
horrible even below that.  Even a great RTOS will only get you about
10us repeatability.  It is always best to use a real oscillator to
trigger sampling.  For some reason, interrupt-based sampling seems
very popular in the radio astronomy world.


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