Help w/(DIY?) serial communication and interpretation

[mad.casual]

Background:
I have a clinical chemistry analyzer, 'the instrument', that is attached to a PC (2.5GHz P4, 512 MB, 40 Gb HD) running Windows 2000 Pro as well as the company's proprietary dedicated software, 'the system'. The software has two options for data output, an DE-9 COM port and a 3.5" floppy. The proprietary software fully supports a wide variety of transmission protocols (Baud, parity, char length, stop bits, ACK/NAK) and the system is currently talking to a POSIX-based system via the COM port.

The Problem:
For various reasons, I have become at least partially responsible for making this analyzer (and the data it produces) available to a wider number of users. Whenever I hook anything up to the system via the COM port, I get ZERO communication. No hyperterminal text transfer, no handshake, nothing. I've checked the port(s) with a VOM and, again, the instrument talks to another system.

I'm wondering if I have to write (if possible) or buy a driver to interpret the data that system spews or if I'm just missing something retarded like not shorting one of the COM channels.

I appreciate anyone's $.02 that they're willing to give.

[DaveLembke]

Is the cable used between PC and device the same cable that works with other systems? If different cable could be cable pin out. Is this a null cable?

I also made myself a serial loopback for testing serial ports its pretty easy to make you send the TX to RX and you can then type in hyperterm and see the text looping back. http://www.hosenose.com/radio/support/loopback.htm

If Baud, partity bits, etc are all set correctly you should at least see something like

F^%$VF&%^ if there are communications but its not able to be translated by hyperterm.

Is there a text string output from the device over serial that shows when powered like system ready etc in which you can reboot the device with the pc running hyperterm to see if you see anything other than nothing.

Only other time I saw a person with similar issue was getting RS-232 and RS-422 confused with Rockwell Motion Controllers that I serviced for 6 years as the lead support electronics tech.

Also if you are using a USB to Serial converter, they can be troublesome for some applications. A dedicated true 9-pin d-sub or 25 pin serial with 9-pin converter adapter is best.

There also used to be a tester like this one http://www.cables4computer.com/Accessories/Cable-Testers_Tools-and-Testers_Premium_Parallel_Loopback_Tester.html that had LED Diagnostics for Serial Com, but cant seem to find one other than parallel com.

[mad.casual]

Is the cable used between PC and device the same cable that works with other systems?...

Thanks much for the $.02. It's always two or three simple problems together that really trip you up. I tested the cable and got intermittent results. Threw it away, and made my own (if you want something done right...). That was half the problem. The query input settings on the software are ambiguous as well, when you turn off queries, it waits for the host to ask for data rather than just sending it out.

Anyway, thanks for your input, I hope I haven't taken up too much of your time.