This is a very simple device that can be used as a man in the middle serial interface. The purpose of this is to inject serial data into a serial stream.
I have some CB radios that require reprogramming from the serial port. When it tried to read the data, the radio needed a 6 digit passcode. After analyzing the serial data from the computer to the radio using a serial sniffer, a python program was made to try and trick the radio in thinking it was the software. The python program did not work and was expected it was changing bitrate during the process.
A plan was made to make a hardware serial switch. This would ensure that the radio would get the correct setup from the computer and then brute force the passcode.
How it works
This is a very simple hardware to connect from the computer to the radio. two serial ports will be used from the computer and one connection from the radio. Two AND gate will be used to switch the connection from the two computer serial ports.
one of the serial ports to the computer is used to proform the man in the middle attack. this serial port will have all data returned from all Rx data lines and the serial port two TX data line.