Logitech harmony volume control via Raspberry pi

[walther]

What I've done is something that i run on a Raspberry pi (3 in my case if I remember correctly) which listens to HDMI-CEC volume up/down from an Apple TV and then sends corresponding UPNP volume up/down to the Phantoms. Inspired by another project, and I also think that there are others as well. My project is very old now but I have not had the need to update it (yet). https://github.com/twalther/phantom-hdmi-cec