Take a look at the schematic. GPIO3_21 is connected to the output of a clock generator. To use it you must disable the Oscillator.
*Oscillator can be disabled via SW* *for power down modes or if* *GPIO3_21 needs to be used* My suggestion is to pick another pin to work with. Less headaches. Gerald On Wed, Jul 8, 2015 at 8:47 PM, <jmschmit...@gmail.com> wrote: > > Hey all, > > I am pretty new to the BBB and I came across something pretty odd that I > have been trying to figure out for a few hours now as I was creating a push > button circuit: > > P9_25 is a GPIO pin. I set it to input but noticed that it would not > respond to my button. After some digging I realized that the pin itself > was acting funky, so I isolated it to run some tests with BB's Bonescript > tutorial on GPIO digitalWrite(). I ran this code below (apologies for the > sloppy picture) with the adjacent circuit configuration shown as well. > Obviously, the LED should turn off, but it doesn't: > > > > <https://lh3.googleusercontent.com/-UVZwTNBSR00/VZ3RjMNpQiI/AAAAAAAAAGM/mjWtyKl5LTw/s1600/20150708_212210.jpg> > <https://lh3.googleusercontent.com/-lmn1_9_NGTM/VZ3PwVv6MLI/AAAAAAAAAF4/-yVeDLNf7fY/s1600/20150708_212158.jpg> > > > I then tried the same tests on other pins, such as P9_26, and it worked > perfectly, so that's where I'm startled. > > > I have two theories: > > > 1) I messed with P9_25 in the past, and it is reconfigured in a weird > way; if someone has this hunch, could you please perhaps inform me how to > reset the pin to its original glory? > > > 2) The pin is busted. Fingers crossed for #1. > > > If anybody has run into something similar, or has any idea what I should > do, please let me know! > > > Thank you for you time. > > > -Joe > > -- > 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. > -- Gerald ger...@beagleboard.org http://beagleboard.org/ -- 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.
