TJF, This is absolutely AWESOME! What a great library! I am just now reading through the documentation and reviewing your recommendations but have a question.. I plan on utilizing a GPIO pin and setting up MM mode and monitoring AdcUdt::DRam[1]. How do you recommend I monitor AdcUdt::DRam[1]? Just setup a loop in python or do you recommend another method? Basically I need to put a timestamp at the leading edge of the input.
Thanks! On Saturday, September 1, 2018 at 12:00:35 PM UTC-5, TJF wrote: > > Hi! > > Am Freitag, 31. August 2018 17:44:22 UTC+2 schrieb > [email protected]: >> >> 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. >> >> 1) Time stamp when the input voltage reaches 0.5v - The geohone is >> generating a sine wave, the stronger the vibration/movement of the >> geophone, the higher the amplitude/voltage of the signal is produced. I >> would hope to accurately place a timestamp at the exact moment the voltage >> crossed that threshold. As far as timing goes, I am using onboard GPS with >> 1 PPS output and Chrony for sync. >> > > libpruio <http://github.com/dtjf/libpruio> is designed for such tasks. > Use it in MM mode (MeasureMent mode). Up to four triggers can be set to > specify the sampling start. Even pre-triggers are possible. See > http://users.freebasic-portal.de/tjf/Projekte/libpruio/doc/html/_cha_features.html#SubSecTriggers > > for details. > > When measurement starts, the value of AdcUdt::DRam[1] drops down to 0 > (zero). So by monitoring that value you can generate a timestamp with > Python accuracy. If this isn't accurate enough, you could use the other PRU > just for the timestamp. > > Next version 0.6 will ship with Python bindings and example sources. > > >> 2) I also have a contact closure that I would like to monitor. Right >> now, I am pushing 1v through the closure, and monitoring the ADC for a >> voltage change from 0v to 1v, then applying a timestamp. Any thoughts here? >> > > Since version 0.4 libpruio can handle GPIO input in MM mode. Ie configure > a pulled-up GPIO-input and groud the pin by your closure. (You can also > continue with ADC input, but in MM mode the data evaluation has to be done > after the measurement.) > > Regards > > >> 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? >> >> Thanks! >> > -- 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/632dd074-1e98-4ca1-836c-3eaa9dc1c5b3%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
