Can ATXRaspi be modified or setup for a non-momentary switch?
I am guessing with no modifications using a non-momentary switch will have the ATXRaspi do hard power off "Forced-Shutdown" mode"?
Yes it can, but it will need a firmware change.
I would very much like this firmware as it would be ideal for car use sensing ACC via an optocoupler.
Secondly, is it possible adapt the firmware so that the uC speaks to the UART of the Pi and issues an halt over UART? This way it would not need any scripting and would work out of the box for Openelec etc.
The chip is an AVR so you could technically change it to do everything you want. The UART part would have to be a software UART since the chip doesn't have a hardware UART but that would not be a problem at all. But mind the fact that it would tie up your Pi's GPIO UART pins for this function, and you'd still need another script to watch for the UART commands come through.
Since this is not stock firmware and is really a custom case I would not be able to develop it for the purpose of selling only a few items, it's not a very good use of my time.
It can take several hours to write the code and the script, test it etc. But it's a perfect project for those who want to hack the stock firmware and do something else with the board :)
Understood, not a problem at all. I'll give it a go and post the results.
You might want to save the existing image before you burn a new one to the chip ;)