Praise Jibbers, I'm an idiot. I misunderstood all the admonitions that "GPIO number" wasn't the same as "pin number." I thought "GPIO Number" was some TI reference, and "pin number" was how Linux referred to the pin. But in fact, Linux (in its infinite wisdom) uses two different labels for a pin, depending on what part of sysfs you're using. Awesome. Just awesome.
To be clear: The "pin number" (e.g. 36 for P8_07) is what's used in /sys/kernel/debug/pinctrl/44e10800.pinmux/pins. The "GPIO number" is what's used in /sys/class/gpio/... > On Dec 25, 2014, at 15:28 , Rick Mann <[email protected]> wrote: > > Okay, I installed the 2014-12-11 bone-console test image onto an SD card, > booted from that, and tried again, with the same result. I guess I should go > back to the version used by Derek Molloy. > >> On Dec 25, 2014, at 03:26 , Rick Mann <[email protected]> wrote: >> >> I've been trying to get input and output GPIOs to work following Derek >> Molloy's videos and book. I'm using Debian 7/3.8.13-bone68. Pin 36, by >> default, is configured as an input with pullup enabled. When I measure that >> pin with a DMM, it's near 3.3 V. But when I try to read the value via sysfs, >> I always get 0. >> >> Here's how things look for pin 36, P8_07: >> >> # cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pins | grep 890 >> pin 36 (44e10890) 00000037 pinctrl-single >> >> # ls /sys/class/gpio >> export gpio36 gpiochip0 gpiochip32 gpiochip64 gpiochip96 unexport >> >> # cat /sys/class/gpio/gpio36/direction >> in >> >> # cat /sys/class/gpio/gpio36/value >> 0 >> >> # cat /sys/devices/bone_capemgr.9/slots >> 0: 54:PF--- >> 1: 55:PF--- >> 2: 56:PF--- >> 3: 57:PF--- >> 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G >> 5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI >> >> Similarly I tried setting the direction to "out", and tried setting the >> value, but it had no effect on the output voltage. >> >> Am I missing a step? I followed the instructions here: >> http://derekmolloy.ie/gpios-on-the-beaglebone-black-using-device-tree-overlays/ >> >> I also tried setting up the overlay as directed later in the example, but it >> made no difference. >> >> I'd really appreciate any help! >> >> -- >> Rick Mann >> [email protected] >> >> >> -- >> 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/d/optout. > > > -- > Rick Mann > [email protected] > > > -- > 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/d/optout. -- Rick Mann [email protected] -- 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/d/optout.
