Hi @fusari,
I’m not really sure what you’re trying to do with this program - you’re requesting all the parameters and then not trying to receive them, and then checking whether a specific message has been received that you haven’t requested.
If you’ve opened up a control station software (e.g. QGroundControl) before you run this Python program then most likely a VFR_HUD messages will be available, because control station softwares automatically request particular message rates. Even in that case, your code currently only works if a VFR_HUD message was received while waiting for the initial heartbeat to be detected from the vehicle, whereas it would make more sense to just wait for the message you want directly, instead of your current try-except approach:
msg = master.recv_match(type='VFR_HUD', blocking=True)
print('Depth [m]': -msg.alt)