Where can I find the default device-tree configuration of GPIO
I want to enable a halt signal on shutdown that I can use to power off the Onion Omega 2's that I have. I have a soft on switch circuit that I want to use for a battery powered device. It works fine. The switch functionality is such that if the lipo is too low it won't enable the regulator and therefore won't power the onion.
To complement that I want the onion to be able to power itself off by setting a GPIO pin high when shutdown is complete.
Exactly the same as this Raspberry Pi functionality...
The device tree is baked into the firmware, and AFAIK (please correct me if I'm wrong) there's no easy way to put device tree overlays somewhere such that the Omega picks them up durig boot, unlike RPi.
If you want to modify the device tree, you'll need to build your own LEDE firmware. This by itself is doable (needs some time and disk space, though), but as Onion still hasn't released all parts of their own firmware you'll not get the same firmware but a stock LEDE. You can add some of their extensions that are on github, but their WiFi driver and other stuff is missing.
Thanks for that, it's very much appreciated. Playing with my own firmware is out because I don't have the spare time :-)
I can use a micro to handle power management; an attiny should do the job. I was hoping for a solution that used discrete components though.
I'm doing a project that will be battery powered from a less than 700mAh battery for periods of about 1 hour at a time. It will be completely sealed and inaccessible so the battery will remain connected all of the time and it will be charged either with a usb cable or via an inductive circuit.
The intention was to have a single momentary push button to turn it on (if there was enough power) and it could turn itself off if the battery dropped too low or it was shutdown via the wifi gui.