Bidirectional Communicating between RCX and NXT - a simple but ingenius solution

It is not often I write about other NXT projects - but this one from Steffen Lindner in Germany really caught my eye - due to its simplicity and the amazing lateral thinking that has gone in to this:

Who needs an IR-Link to bridge between NXT and RCX when you got this?

The solution has an RCX light sensor reading the LCD of the NXT, and a NXT light sensor reading the IR port of the RCX. Impossible? You need to see the video to believe it!

More info on



Laurens Valk said…
That is a possibility.

But, can it send more than one signal?

I think that light sensor to light sensor communication can be much more powerful.
Unknown said…

Yet, in real models it's often hard (or impossible) to cover the display of the NXT that way.
And it's rather inconvenient, as you are required to watch the LCD in many real-life situations.

But still, as nice example of thinking around the corner. :-)
Andy said…
My good friend,

It is impossible to make bi-directional communication with only 2 light sensors (1 RCX style, and 1 NXT style) since the RCX on can't turn itself on and off like the NXT one. You are required atleast 3 wires to do that with an analog sensor like those light sensors.

Laurens Valk said…
In NQC (for the RCX), you can 'switch' the light sensor to a touchsensormode. This will turn off the led light.
I used this method in a robotic arm of mine.
Though there is no bi-directional communication as I did not need that for this robot.
Micah E. said…

Like laurens said, it is indeed possible to turn the LED off in the RCX light sensor. RoboLab can do it, it's just RCX-code that can't.
Anonymous said…
By connecting the NXT to the RCX with the convertor cable, I've gotten the NXT to send the RCX any of 255 different messages (although so far I've only coded 30-something, and I don't plan on going past 40 or so).

Andy said…
This comment has been removed by the author.
Andy said…
Anonymious, I've been thinking of something like that, bust sadly my RCX is dead so I can't test it
:-( If I get it to work I will try to do something like that too.


PS. Blogger "cut" a word so I deleted it and edited it.
Anonymous said…
That's so cool!
Gary n said…
I have done this using light sensors that can send numbers between 0- 255 to and from NXT and RCX.


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