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

[David Forbes]

Hello all,

As part of my radioastronomy job, I'm being asked to devise a low-cost 
pulsar detection machine for very high frequencies (~80 GHz), which 
requires many tens of hours of integration time staring at the pulsar 
while maintaining absolute timing accuracy of ~50 microseconds.

I have GPS time and a maser available for absolute and relative timing 
respectively. I expect to be taking the data via a low-cost A/D card 
clocked by the maser at about 100 us per sample. I plan to use RTLinux 
unless I can be convinced there's a better way, as I already use 
RT-Linux successfully for our various spectrometers.

My question is: What's a good way to synchronize the RT-Linux OS clock 
to the GPS clock? I am considering the use of the A/D card's interrupt 
with the 1PPS from GPS. I expect to use NTP to get the correct second.

Does NTP provide a way to tie an interrupt from some user-provided 
hardware to sync up the fast clock to ~50 microsecond accuracy, or is 
there some other method?

Thanks in advance for any help.