On Friday, August 31, 2018 at 11:44:22 AM UTC-4, [email protected] wrote: > > Hello, > I am interested in using the BBB to monitor a sensor (geophone) at about > 200-400sps. I am currently using the Adafruit_BBIO.ADC library to do this > in Python. Ultimately, there are two goals for this project, and I would > love some input on how to approach this. > ...snip.... > I have read about the PRU on the BBB and am wondering if that is what I > need to be using to obtain sub millisecond accuracy on my timestamp. Any > thoughts here? > > Sub millisecond time resolution can't be done from user space. My own experiments using the Beaglebone's built-in A/D converter to make voltage measurements from a user-space program show sampling time jitter of around 5ms. This is OK for doing measurements of a slowly varying or DC signal, but is not good for doing anything approaching audio speeds.
One possibility for you is to use the ADC-001, which is a sampling A/D designed for audio and DSP applications. More information about it is here: https://elinux.org/ADC-001 It is an open hardware project, so schematics, driver, and several example codes are available for download. Drawbacks for you are the code is in C, and the low-frequency cut-off of the circuit is 50Hz. Of course, you can always learn C, and if you're adept at electronics you can easily modify the board to work down to DC. Full disclosure: I am the ADC-001 designer, so I am always interested in seeing people use it. Stuart -- 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/c1c06948-9a1e-4699-8373-cfd1c61b3600%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
