On Thu, Dec 1, 2016 at 10:39 PM, acheesehead <acheeseh...@gmail.com> wrote:

> In all of the examples that I have seen, the P9.x -> GPIO bank.port
> translates to GPIO (bank +1).port between lines in the overlay script.

That's incorrect if I understand what you're trying to say. the P8/P9
header values for the pins have absolutely no correlation to the kernel pin
values. These values can be gleaned from the schematics. But I typically
use something like the attached file( in pdf format ) that lists all the
important data I need.

For example P9.22 has a kernel gpio value of gpio0_2. What this means is
that the pin is on gpio bank0 ( bank zero ), and is pin 2 of that gpio
bank. Note, that on the beaglebone there are 4 GPIO banks. gpio0-gpio3. Now
with this in mind. to figure out the sysfs gpio number you would . ..

gpio_bank * 32 + pin number. So, for the sysfs file entry for the P9.22
pin. Our pin would be gpio2. But for example, and arguments sake. If this
pin were on gpio_bank 1, then the sysfs entry for this pin would be gpio34.
gpio_bank 1 * 32 + 2.

Irregardless, I just gave you a step by step, exact steps recipe to
success. That I wrote as I figured it out for the first time myself.

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