Sorry but the problem is not the TX Buffer of the SAMD... so sending data is not the problem.....
The problem is receiving data from another chip ON SERIAL 1.... "ready/status calls" are not possible so the best solution so far for me would be a change of the RX-Buffer size of SERIAL 1.
westfw you mentioned that " the Adafruit SAMD code doesn't HAVE a tx buffer at all."
.... but i guess there needs to be a RX Buffer size, right???
The normal "SERIAL" is not the problem , the only problem is receiving data on SERIAL1 , the buffer is 64bytes .... so this size has a declaration somewhere....
Maybe anybody has another idea where I can find it???