Thanks, I'll try to see if there is a difference with libsoc or not. However, I did manage to get it working with low level unix i/o (open, write) instead of the buffered stream i/o (fopen, fwrite). It works correctly, I didn't need a seek operation, and I was able to get pulse widths down to 10uS reliably. Interesting difference though: fwrite to "/sys/class/gpio/export" succeeds even if GPIO30 was already exported, but write to "/sys/class/gpio/export" fails if GPIO30 was already exported.
In case anyone's wondering why I'm trying to get really short pulses, I'm trying to connect an iGaging DRO slides to a BeagleBone Black (yeah, I'm trying to CNC my lathe using a DRO closed loop servo with my Dual Motor Controller Capes). Scoping out my iGaging DRO, I found that the builtin controller uses 24uS pulses with a 128uS duty cycle. I'm working off of Yuriy's work on the Arduino (http://www.yuriystoys.com/p/android-dro.html), but trying it on the BeagleBone. Paul Tan. http://exadler.com http://exadler.blogspot.com On Friday, October 18, 2013 1:26:31 PM UTC-4, Jack Mitchell wrote: > > On 18/10/2013 18:14, Paul Tan wrote: > > I'm having some weirdness that I don't quite understand. I'm trying to > > just toggle a GPIO pin (GPIO30) on and off using C and just the file > > subsystem. Everything seems to work if there is a delay between the > > fseek and the fwrite. See this pastebin for the relevant code > > http://pastebin.com/Ftvv0nvE. As it is, it works. If you uncomment > the > > code, instead of creating a square wave on the oscilloscope, it just > > creates pulse spikes (i.e. short on times). Can someone explain what is > > happening? I'm working off a stock BeagleBone Black, no updates (I > > wanted to make sure the code worked on all versions, as people would be > > getting their BBB and trying it directly). > > > > Paul Tan. > > http://exadler.blogspot.com > > http://exadler.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 [email protected] <javascript:>. > > For more options, visit https://groups.google.com/groups/opt_out. > > Hi Paul > > If you don't object to using a library there is libsoc[1] which is made > for this exact purpose. If nothing else, you could see if the same > behavior is observed using it? > > https://github.com/jackmitch/libsoc > > Cheers, > Jack. > > -- > > Jack Mitchell ([email protected] <javascript:>) > Embedded Systems Engineer > http://www.embed.me.uk > > -- > -- 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/groups/opt_out.
