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.
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. http://www.lammertbies.nl/comm/cable/RS-232-spy-monitor.html
The monitoring or spying PC can be simply running something like hyperterminal. You can save the data to a log file for later analysis.