Hi Robert, Thanks for the quick reply. I am already using a custom overlay and using the PPS/GPS tools...
trying PPS source "/dev/pps0" found PPS source "/dev/pps0" ok, found 1 source(s), now start fetching data... source 0 - assert 1548882288.001021883, sequence: 3727 - clear 0.000000000, sequence: 0 source 0 - assert 1548882289.001020522, sequence: 3728 - clear 0.000000000, sequence: 0 ^C On Wed, Jan 30, 2019 at 3:01 PM Robert Nelson <[email protected]> wrote: > > On Wed, Jan 30, 2019 at 2:54 PM Thomas Remmert > <[email protected]> wrote: > > > > Hello, > > I have a contact closure switch connected to P8_14. When the switch is > > activated, P8_14 is brought to ground. I need to apply a time stamp when > > this occurs with millisecond accuracy. > > > > 1) I have an adafruit GPS with 1 pps output. I see the NMEA strings and > > have confirmed the 1 PPS is working. > > > > 2) I have NTP running with my local GPS and 1PPS source configured. (Maybe > > chrony is a better choice?) > > > > 3) Just for testing, I am using the following python code: > > > > import Adafruit_BBIO.GPIO as GPIO > > import time > > import datetime > > > > GPIO.setup("P8_14", GPIO.IN, pull_up_down=GPIO.PUD_UP) > > > > #GPIO.add_event_detect("P8_14", GPIO.RISING, callback=my_callback, > > bouncetime=1000) > > > > while True: > > GPIO.wait_for_edge("P8_14", GPIO.RISING) > > ttime = datetime.datetime.now() > > print(ttime) > > > > > > When I compare my time with a very expensive DAQ, my time stamp is always > > off by 2-4ms and it is not a consistent offset. Does anyone have any other > > thoughts at to how I might approach this? I am needing to get the > > timestamp accurate to 1ms. > > Use the pps driver, setup an overlay like shown: > > https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/PB-UART4-TESEO-LIV3F.dts#L63-L71 > > Then you can use the pps/gps tools... > > Regards, > > -- > Robert Nelson > https://rcn-ee.com/ -- Thomas Remmert Cell: 936-647-6030 Office: 281-203-0855 -- 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/CAGiPVCua3F%3DUGFiyBReQ02cWk3oo-ykJJnAU2-%3DwWo9Ju7dLVA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
