Hi, has anyone seen an Arduino RS232 sniffer? I`d would like to put a device in between an RS232 cable to see teh ASCII traffic in between devices.
Why do you need an Arduino, a simple USB Serila adapter will do the job ?
You cannot connect RS232 directly to the Tx Rx pins on the Arduino because the voltage levels are wrong and you may damage the board.
You can get RS232 shields for the Arduino. By connecting the ground and Rx on the shield to the ground and either the Rx or Tx of connection you want to sniff you should be able to see one half of the communications.
You probably need to consider the baud rate of the data on the line you are tapping into, and whether the data is continuous. If the data rate is high then you will need to be sure the Arduino can process and store it fast enough. Different shields probably have different buffer sizes and buffering will help with high data speeds.