Hello everyone,
on my desk lies a piece of hardware with some dual color LEDs connected to
some IO ports. The LEDs shine green or red depending on polarity and are
connected in between two data output lines or GPIO ports like this:
------.
| LED
P1 |---->|-------.
| ___ |
P2 |---|___|-----'
|
------'
The logic table is this one:
P1 | P2 | LED
-- + -- + -----
0 | 0 | off
0 | 1 | green
1 | 0 | red
1 | 1 | off
So there are three states: red, green and off, red and green are mutual
exclusive, both colors can not be switched on independently at the same time.
I guess this is a quite common setup in embedded electronics, but how would
one model that with Linux? How would I describe it in device tree and how
would the sysfs interface for trigger etc. look like?
Greets
Alex
