I've never tried communicating with one of these pumps (apart from "Teach and Learn" between pumps)* ... and the only thing I remember about the RS-232 option is that it needs to be enabled
via code 251.
Lastly ... I guess you don't have an RS-232 "breakout box" available to you? One would be very handy, as it can be used to watch what (if anything) is going on (lamps flashing indicating a signal, and so forth). Very useful when playing with stuff like this. But you could always make up your own equivalent (after sacrificing a serial cable), and using a 'scope.
*
RS-232 has to be turned off (disabled) for "Teach and Learn" using the IrDA ports.
