On Thursday, August 6, 2015 at 7:18:03 PM UTC-7, Dcap wrote:
windows XP
single serial port 9 pin

Well, that's probably an EIA232 port, of the IBM 9-pin flavor.
But the other end could be RS-422 (Macintosh style serial port), or RS-485,
or have almost any pinout. So, have you looked at its quiescent voltages
with a voltmeter? EIA232 input pins float around ground, and output pins
are (+) when inactive. The data output pin on your 9-pin port on the
computer is undoubtedly IBM-style wiring, TXD- is on pin 3.

If the controller has the same wiring as the computer, its pin 3 will have
the same quiescent voltage signature, and a straight-through cable won't work.
Null-modem cable is required.