On Wed, Oct 5, 2016 at 7:45 PM, Nick Sayer via time-nuts <time-nuts@febo.com > wrote:
> I notice periodically that the phase measurements seem “noisy.” You can > see that over the course of several seconds the value doesn’t change, then > it jumps a bunch and then comes right back. > Hi Nick, At one point I had a problem with noisy phase readings where the "noise" took the form of an occasional reading that was low by up to about 50 counts. These events were quite rare - less often than once per hour on average. After much head-scratching, it turned out that I had an interrupt conflict that sometimes caused the PPS interrupt to be delayed, Because the ADC was triggered inside this routine, the analog signal had drooped a little before the ADC was triggered. I was able to completely solve this by setting up the ADC sample/hold and conversion to be triggered directly by the PPS signal, thus eliminating any dependency on the interrupt latency. The PPS still generates an interrupt, but in the interrupt routine, all I have to do is wait for the ADC to finish, clear the Done bit, and reset the trigger. -- --Jim Harman _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.