[lynca]

Use the program port on the RC to communicate to the second camera over RS232 not using TTL, get kevin watson's serial ports code to talk over that serial port.
There are a few different ways of communicating to the camera over a serial port, i suggest starting with kevin watson's documentation and then move to the two camera code posted by FIRST (as a reference on protocol format).

This will be difficult to debug, so you might consider using the user byte format which is sent to the OI. You can use the dashboard (available from IFI ) to read the user byte format.