Hi - I was thinking about offering an extension to slimproto to be able to report Battery Level and Voltage.

The idea would be to add a capability in HELO like "battery" and then to append to STMs messages two u8: voltage x 10 and battery_level (in%). Value of 0xff means "I don't know".

This way, we would have compatibility with existing LMS & devices: the addition to STMs are ignored by previous LMS versions and for the new ones, they are only relevant if we have received the "battery" capability in HELO (the extra HELO field is ignored as well by previous LMS versions). Although I also think we could even make the HELO extension optional as probably the size of the STMs message could be a good enough qualifier, I was just thinking that explicitly declaring the capability would be a better practice for further extensions.

Is there any interest from the pure squeezelite point of view and PiCorePlayer? Other suggestion & opinion?