The logger and receiver both run at 9600 bps when transmission works ok. the files are very large up to 60 megs but will get much longer later in development. I have an intense interest in getting speed up but in addition to trying to absorb Nick's counsel you kindly referred me to, I'm going to do more googling to see if i can come up with a way to isolate the sd writing from the serial input. It could be that better buffer handling will allow increase in speed.
the nature of the data can tolerate random errors but I think error toleration can cascade into indifference and I may find that i need every byte for short period records - just don't know yet.
and i think the system does need a handshake.
But then, I'm not there yet.
thanks for your interest. all ideas welcomed.
john