Just doing some pre-reading again. The serial port is supported by the commands:
SWRITE function block if the receiver is unable to receive?
Otherwise, I can see that I would have to manually write a function to implement XON/XOFF protocol, since there are no control lines allocated. (The hardware that I've ordered also doesn't support hardware control, only Tx/Rx).
Looks like I'm going to learn about XON/XOFF.
Update: OK, that was quick...doesn't look like I can implement XON/XOFF, as I can't read serial bytes.
@uli , are there other UARTs that are available to use for serial, other than the one attached to the audio out?