Why not write this with a Kernel Module: http://derekmolloy.ie/kernel-gpio-programming-buttons-and-leds/
This is much faster and will do what you want. Regards, John > On Apr 2, 2016, at 7:42 PM, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote: > > > o/~ I'm Talking to Myself in Public o/~ > > On Sat, 02 Apr 2016 21:37:26 -0400, Dennis Lee Bieber > <wlfr...@ix.netcom.com> declaimed the following: > > > >> I attempted to generate something in C++ which took hours. For some >> reason I can't seem to find a GPIO pin that was actually toggling when >> under an oscilloscope. Even when manually setting the pin value using the >> echo 1 > /sys/class/gpio/gpio#/value >> from a command line. I could read back the 1 (or 0) value, but never found >> a level change on the 'scope -- the pin was either tied high, or tied to >> ground. >> >> My last version is showing some activity, but is still failing, as >> shown (I'm wondering if usleep() has some obscenely large granularity on >> the BBB, because it took 53 seconds to go from "beginning measurement" to >> the first timeout error on the first byte, sixth bit): >> > > Actually, I suspect it's the overhead of all the I/O calls needed to > access GPIOs via a pseudo file system. > > After all, to detect a 0 bit, requires being able to do three at least > six I/O function calls in 27usec (the HIGH period of the bit -- > open/read/close to detect the transition to HIGH, and open/read/close to > detect the end transition back to LOW -- and preferably multiple cycles to > get some idea of the length) > > Might need to try the mmap route... Hopefully won't need the PRU. > -- > Wulfraed Dennis Lee Bieber AF6VN > wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/ > > -- > 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 beagleboard+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
