On 2015-02-07, Rob <nom...@example.com> wrote: > William Unruh <un...@invalid.ca> wrote: >> On 2015-02-07, Rob <nom...@example.com> wrote: >>> walter.preunin...@gmail.com <walter.preunin...@gmail.com> wrote: >>>> Ok, so these questions might be off the wall. >>>> >>>> Is there any reason why I could not share the PPS output of say, my u-blox >>>> 7 GPS module on multiple computers? Would it be good or bad to peer these >>>> 2 systems with each other? >>> >>> We do that in our project to synchronize several systems to the same >>> GPSDO accurately. We use surplus "video distribution amplifiers" because >>> they neatly fit into this (BNC In/Out, correct levels). There also exist >>> dedicated devices for this. >> >> Actually the biggest problem with this is that it takes time to service >> a gps interrupt. Thus the first pps to come in, or be serviced delays >> the servicing of the second interrupt. Thus the accuracy of the two GPS >> is very ( 10-20usec) different. (I call that "very" because a gps pps is >> capable of 1usec accuracy, so a factor of 10 worse is alot) > > No, the single PPS is fed to multiple systems that each service the > interrupt at the same time.
I was answer the question as to whether one could feed more than one pps to a single machine. > > I presume you meant this followup to the "multi PPS sources to a single > system" and then it is not true either, of course our systems have > at least 4 cores and they can service multiple interrupts at the same > time. OK, if that is true. AFAIRemeber I did my tests on a 2 core machine, and had trouble with interrupt blocking of the one pps on the other, but I could be wrong. If you have tested it, that would of course trump my vague memory. If you are going on theory, I would test that first. You could even just take one PPS and feed it both to the serial port and Ack on the parallel port (assuming such a thing exists on your system) as a test. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
