> Of things interrelated, I wish to sample a 10kHz square wave into a GPIO, > which I am certain the RPi will do, see my earlier post with link to RPi > forums. This will be a constant signal (an output of a GPSDO, with > potentially a rubidium oscillator backup). So while the 10kHz is constant, > the users input is not, and I wish to correlate in time the users input to > the rising edge of the 10kHz signal, as it is then to be sent over a > network with the time data of the event. [...] > > I could be wildly off here Erik in my way of thinking, but my motivation is > to extend the syncfs module to correlate precisely in time. The example > system used by the Indiana University had no synchronisation across the > network - presumably the only synchronised filesystem was the local > filesystem on the cart robot? I will also be writing some kind of memory > bounding for the ramfs. So, the events themselves are asynchronous and > non-deterministic, however the clock source against which the events are > placed in time is deterministic, and allows for easy reference and auditing. > > Perhaps there is a better way of doing this, I am not sure. Remember, I am > an outsider to Plan 9 ways of thinking, although I am mostly unspoiled by > Linux ways of thinking. To be precise, my ways of thinking are MSDOS, if > that is at all possible in this day and age. I accept any and all better > suggestions.
it seems that the system timer is already 1mhz. but i suppose the issue is that there is no external reference. do you think you could get .1 ppm time resolution with ntp between raspberry pis? if not, i don't think i know enough about your setup to say much of use other than to note frequency is not directly related to precision. if local timing can is stable to .1ppm for a longish period of time, then a low-frequency strobe of high precision and known timing could be enough. the bbc does this with the tone at the top of the hr. - erik
