The Warnings...

… in the header file used to interface with the serial chip seem to be quite appropriate. It is not really rocket science to send and receive data, but it is pretty difficult to pinpoint any problems because they are usually timing related. I made some changes in the sending part which enabled more stable OBEX operations with Blunt 2, but it looks still a bit incomplete - sending data in large batches results in errors on the receiving end, which hints at some data corruption.