I have a controller that talks rs232 ,driven by a MAX232.
3 wires only. I connect the computer to it: works fine. I am connecting a StarTech NETRS2321E Net adapter to it. Won't work. Loopback plug instead of controller: works fine. Since the harness on the controller side includes a DB9 tap I decided to hook the computer into that, and LO! that causes it to work! I get communication on both channels , one from serial port, one from NETRS232. If I unplug the serial port cable at the controller the NETRS232 quits receiving data. If I unplug the serial port cable at the computer the NETRS232 continues receiving data. What is going on? What changes to the controller circuitry would help? Cheers f