This topic is old, but I will reply if it is found through search functions: I found a solution, what can be applied with small external hardware modifications. It is possible to take some measurements on HAT interface's pin "5VIN". Measured voltages: If powered by USB: ~4.7V Powered by battery and switched off: ~0.7V Powered by battery and switched on: ~2.4V Using voltage divider with two same resistors, we get usable logic values for HIGH and LOW ( ~2.3V and ~1.2V). The measured values are not inside garanteed logic range but as a workaround: it works well. Maybe it helps someone else...