On 2/25/2015 8:34 PM, Rick Mann wrote: > I need to accurately measure frequency from a pressure transducer, > and make it available on a LAN. A BBB ought to be able to do this, if > the PRU can be made to accurately measure the frequency. > > The frequency range is 30 kHz to 42 kHz. I need better than 0.01% > accuracy. Overall latency in the reading is not too much of an issue, > so long as it's not more than a few seconds. > > Does the PRU let me connect a GPIO to a counter internally? I can > measure some cycles and compare that to a crystal-driven counter. > > Has anyone done this?
Since you need about 2 nS resolution, I'd recommend using the hardware timer capture registers and averaging several samples. Using the PRU to read a GPIO takes about 165 nS with a fair amount of potential jitter in the timing depending on clock synchronization and how busy the interconnect fabric is at that moment. The hardware capture timers will only be limited by their clock frequency, and you can average a bunch of readings to get sub-clock cycle resolution. -- Charles Steinkuehler [email protected] -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
