Communication between robots in VEX U

Hello, my team is moving into VEX U next season and we are wondering what sort of communication between robots is allowed. We have found VEX link, however states: No radio communication is allowed between Robots. However, other non-radio forms of communication are permitted (i.e. IR, ultrasonic, etc), which means that it’s illegal. That leaves the other option: non radio communication, however we are not sure what VEX counts as non radio communication, since IR is allowed, it means it’s not the electromagnetic spectrum.

The question is: what electromagnetic frequencies are we allowed to use for communication between robots in VEX U?

Ideally we can just use VEX link (and it’s poor bandwidth, but it should be enough for what is needed) in VEX U, but I have heard it’s VEX AI only.

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According to the REC Foundation website regarding VEX LINK:

The VEX LINK communication system uses a second VEX V5 VEXnet radio connected to each V5 Robot Brain to establish a robot-to-robot link.

Because it’s using a second VEX V5 VEXnet radio to establish the link, wouldn’t that make it another form of radio communication? That would mean it would be illegal per VUR11.

You can make the V5 brain on one robot display color codes, and use the vision sensor or color sensor on the second robot to recognize the code. That’s the most I can think of that is simple yet legal

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Could you elaborate on what you mean? I don’t quite understand what you mean by “try again”

Your response feels unnecessarily hostile

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If IR is expressly allowed despite being electromagnetic radiation, why wouldn’t visible light be?

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The V5 brain itself displays color regardless if we tell it to do so or not. All you are doing is reading what is printed on the V5 brain with a VEX-Legal sensor. I feel like common sense would rule it legal, especially considering a number of teams using LED light strips on their robot.

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With VEXU it is legal to use lights as a legal sensor to give visual feedback to the driver about the robot (like indexing a ball is indexed without error, or the flywheel has shot a ball, then change the light to a specific color). That being said, having a sensor on one bot that reads light emissions from another bot should not be illegal.