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I need to verify what's being output on an RS232 port of an appliance that's running proprietary software (e.g. NOT Windows or Linux). The port is sending data to a target app on another appliance, but I need to verify/log the actual data raw outside of the appliances. Would appreciate a recommendation on process/software to attach to the physical sending port (I have a straight through RS232 cable) and grab sample output of that port.

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Years ago we got away with putting together an RS232 tap which consisted of a couple of diodes connected to the transmit and receive lines. This was so you could see data in both directions. Often RS232 protocols are half duplex request/response although not always so you'd get whole request/response messages on the monitoring terminal. If your data is full duplex then you'll need to monitor each direction separately.

Heres the concept.

The monitoring or spying PC can be simply running something like hyperterminal. You can save the data to a log file for later analysis.

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