Having Problems Pairing Controller with Brain

We have a controller that was used on another brain since we couldn’t find the previous controller. We tried pairing this controller with the brain on the robot, following the instructions provided on the Vex Robotics Youtube video. However, no matter how many times we try, they would not pair. When we plug in the tether cable between the brain and controller, the tether indicator shows on the LCD screen. However, once we disconnect the tether cable, we do not get the signal strength bars… we get the animation that it’s trying to find a radio signal. Anyone know what else we are missing, or could go?

Are the VEX IQ radio modules the same color?

Yes, both are the blue smart radios.

Easiest next thing to try would be making sure they both have up-to-date firmware (make sure controller is tethered during firmware update, etc.). If that still doesn’t do it, you might check that the radios are seated well. At that point if it still didn’t work I’d be out of ideas and ping a VEX staffer.


Yeah, we were wondering about the firmware if that was a possibility. We had already tried reseating the radios on both the brain and controller, and that didn’t work either. Will try the firmware as last option.

OK, it might be the radio on the controller that is bad. Tried VexOS update, but the brain and all motors and tethered controller have the latest update (v2.1.3). We tried pairing the controller from one of our other teams and that worked without any problems.

When you plug the brain and controller together and plug that into the PC and run the VEXOS program, does it show both radio’s (little icons on both the controller and brain). I’ve run into cases where the radio is not plugged the entire way into the robot.

I’ve also had cases where there was a bent radio pin.


I don’t have the robot and controller right now, but will take a look later in the week when the team meets.


Sorry, got pretty busy the past week. Yeah, plugged in the brain and controller, and connected to VexOS. Both radios do show. It does look like it’s a bad radio.

@spaghetti_code Did you get this fixed? I’m interested in what the final answer was.

Normally if the VEXOS display shows the radios they are working.


@Foster now rereading your post, I didn’t realize that the radios also show up individually. I had to rewatch the Youtube video and pay careful attention to the little radio rectangles, especially the one on the controller. Now you mention that, I retried and no the radio on the controller doesn’t light up on the outline. The controller does.

@spaghetti_code Ok, so try this. Take the back off the controller. Take the radio out. Look at the pins in the controller to see if any are bent. Then put the radio back in, push to make sure it’s seated. Then reattach the back.

Now try checking with VEXOS and see if it shows up. If not, then the radio has an issue, try swapping it with another radio. (If you don’t have a spare one, swap with the brain and see if it shows up).


Yes, we did the swap with another controller radio. The radio (bad) from the first controller also did not work when put into the 2nd controller. The radio from the 2nd controller was put into the first controller and that worked. Thanks for your help. I think the issue is with the radio.

1 Like

@spaghetti_code There you go, diagnosis confirmed, ask support@vex.com to replace it.

If you teach your roboteers nothing else this season, what you did to swap stuff around to figure out what’s broken is priceless.

How to figure out what’s broken is 99% of the battle!