I'd like to use a Leonardo to turn the power on and off to my htpc, as well as use it as the ir receiver.
I have the Leonardo interfaced to an ir receiver and have it converting the received remote signals to usb keyboard commands and it runs XBMC just fine.
I would like to use the pc's standby power feed to power the Leonardo, but I also want it hooked to the usb port so it can pass the remote commands.
My question is, will powering the Leonardo via the standby power feed hooked to the 5v terminal on the board cause any problems like a back feed or something when I plug the usb port in?
OK, I think I've figured this out. There probably would be a problem with back feed however I think it can be overcame pretty easily.
I want to mount this internal to the htpc and I planned on interfacing to an unused usb header, so I'll just scab a usb micro cable to a usb header plug and leave the red power lead disconnected. That will allow the Leonardo to run on the pc standby power and not allow the back feed to reach the motherboard.
Just an update - this works fine. I had pc case card slot bracket with two usb sockets in it that plugged into a motherboard header. I took one off the bracket and lifted the red lead out of the header and connected it to the purple standby power lead. I then plugged a usb to micro usb cable into that and it powers up the Leonardo fine when the pc is off.
The project works a treat - turns the power on and off via a relay interfaced to the case power switch and it also receives the ir remote commands and sens keyboard presses to xbmc, a nice tidy little project that's very handy - really nice to be able to turn the pc on and off from the couch!