vexnet connection issues

Recently, our vexnet connection stopped working. For example, whenever it hits a boundary or anything that jolts it, including sharp point turns, the vexnet key loses connection. However, when we physically push the key into the cortex, it starts to connect again. We called vex tech support, and they told us that it wasn’t a cortex issue. So, if it’s not a cortex issue, then what is it?

You should pay attention to the cortex when it disconnects. This will let you know if it is a problem with the key or the cortex, even if support has said it was not a cortex issue.

There is a possibility that your vexnet key is bad. Since it happens on sharp turns, I’d assume the key on your robot is bad, and not the key on your controller. You should try test both, just to be sure.

The other possibility is that your battery is being jiggled loose when you bump into things. You can try making your battery wire more firm when you plug it in, so that it won’t come out unless you pull it manually.

Sometimes it could be both the battery’s fault and the cortex’s. It could be this rare issue that I had once before. The prongs inside the cortex might be loose in some way. This happened to me at worlds before (I don’t remember which part it was exactly, because it was 2 years ago), and I didn’t have an extra cortex, so I fixed this in a way by zip tying my battery wire whenever I plugged it in so that it wouldn’t jiggle at all.

It could be a cortex issue. It is possible the USB connector is loose from cables/keys being shoved in the cortex. In my experience, this is less likely that the keys being broken or something wrong with the battery leads on either the battery or the cortex. So while they are possibly correct, tech support is wrong by saying it is definitively not a cortex issue.

The best thing you can do is narrow down what the issue is: battery or vexNet and which component is the issue. Try different key combinations, battery combinations, on at least two microcontrollers. Other than figuring that out, there’s really not much else I can recommend. Try out what MGOD said, I’m sure other people will have more in depth pointers.

In summary, don’t completely rule out the cortex, although you should be skeptical of it truly betting the issue.
Hope this helps!

Are you running a backup battery? I use to have the same problem quite frequently. The backup battery helps a lot with connection issues.

We finally solved the issue!

However, the final solution was rather mundane, since the final problem (we suspect there were multiple problems at different times) was that the vex net key wasn’t pushed in fully. Thanks for your help, as we tried all of your solutions :slight_smile:

How did you guys end up solving the problem? We’ve been having the exact same issue over in Cherry Hill lately.

Tape the key in. With Electrical tape. Have one person shove the key in, and another put taught tape on that key, pulling it towards the USB socket. We HAVE to do it on one of our robots, or it stops the Autonomous mode because of a consistent disconnect. This fixed our problem.

I don’t know if VEX has this anymore, but I remember our VEXnet keys coming with velcro pads that stuck onto the cortex and the key.

Those velcro pads were what ruined all of our keys because you had to lift the key up to undo the velcro and then pull out. Angling the key up ruined some keys and one cortex.

Vex no longer recommends using the Velcro pads for the reasons listed above. Their new suggestion is to tape the key using electrical tape. The best way to do this is with about a 4 in piece over the end without the connector. So the middle of the tape over the end and then wrap both sides that hang over the key onto the side with nothing on it on the cortex. Sorry the setup is hard to explain i will try to post a picture later.

This has worked the best for me. Hope it helps.