jferg:
I might add that the code above produces a lot of errors in the SD file running even at 19200 bps.so it's very clear that this isn't the way to do it.
Got any idea of why besides bad output?
What baud rate is the logger sending? How long is the data dump from the logger and can you change that serial dump to include software or hardware control, some sort of handshaking or protocol to let the MCU bite off 512B chunks to block-write to SD before the next transmits.