RCX to RCX communication via two light sensors

With NXT, LEGO probably forgot one important thing : people might want to communicate with their good old RCX. But there is no easy way to do it. Third party companies already offer a device. While trying to establish a simple LEGO-only communication between NXT and RCX, we got thought of using two light-sensors as opto-couplers and switch the sensors' lights on and off. So, we first wanted to try the limits of such a communication by using ULTIMATE ROBOLAB and doing it with two RCX. The trick is to switch the sensor configuration alternatively from "powered" to non-powered".

The following has been programmed with Ultimate ROBOLAB. People who don't like IDE's can consider the programs as flowcharts and deduce how to program their bricks using text-languages.

1. The physical experimental set-up :

2. The protocol :

With this setup we can establish a reliable asynchronous communication at 12.5 baud maximum. Not famous, but for many applications this is more than enough. We have the advantage that we sacrifice only one port on each RCX and we can do everything bi-directionally !!!

3. Sending :

4. Receiving :


==> With some effort, it will be easy to set up a reliable but slow optical communication between RCX and NXT with nothing else but LEGO parts. (For the purists : the tape could be replaced with black box made of LEGO bricks.


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