I've recently been upgrading Boland BVB25 OLED monitors over their RS232 serial ports; aside from needing a USB/serial adaptor (I use the Keyspan which mimics an old PC serial UART) you also need a null-modem cable (i.e. where Tx and Rx are swapped over). You can tell if a null-modem cable is required by the sex of the connector on the back of the equipment. A 25-way or 9-way D(male) indicates a DTE ("Data Terminal Equipment" - a PC or terminal) and a female connector a DCE ("Data Communication Equipment") - a modem in RS232 speak. So, if the gear is a DTE then you need a F-F cable and by definition is has to be a cross-over (AKA "null modem" cable. I've banged on about this in the past, and there is also the consideration of handshaking; does you gear/app need the hardware pins (DSR, DTR, DCD etc) or does it use software flow-control (XModem etc). Hugh and I did a podcast on the subject if you need to brush up on your serial comms.
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This kind of three-finger tomfoolery really reaches a zenith when you're upgrading the Linux SOC kernal on Amulet DXiP cards!
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