Debug Library for Arduino

hi matthijs
as I wrote, I mentioned this one https://github.com/mirakonta/lmic/tree/master/hal --> debug.c/.h
It's missing here https://github.com/tftelkamp/arduino-lmic-v1.5
what I expect is to dump if a connection is established, to what gateway a packet is sent/received from (with it's content) and if something fails, a corresponding error code (e.g. timeout, radio not responding, ...)
and yes, printf would be nice.
if it's easier in the existing hal or lmic libs it could be enabled by #define LIBDEBUG and #ifdef LIBDEBUG as an example.