VexNet Connection Problems

I was wondering if anyone know why a vex net might be having trouble connecting between a controller and a robot. Our vex net is having trouble connecting and then it will disconnect. Is there any way to fix this? Will a usb extender help? Could I mount higher on robot with extender?

There are a lot of reasons why this might be happening and we need some more information.

What kind of lights are you seeing when you turn on both the cortex and joystick in an attempt to connect them?

You said that your VEXnet is “having trouble connecting” then “disconnecting.” Does this mean that it takes a long time to connect (but it does connect) and then disconnects shortly afterwards?

Where is your VEXnet key/cortex on your robot? This isn’t usually a problem, but if you really are surrounding your key/cortex with a lot of metal or other electronics, it could be a problem.

Some things that would cause disconnects:

  1. Bad battery connection where bumping the cortex can cause a VEXnet reset as if the cortex had been turned off then turned on.
  2. Bad VEXnet keys - if this is the case you will need to contact a representative and have your keys sent in to be repaired/replaced
  3. Some sort of wireless signal (old VEX crystals?) being used in your vicinity that could be interfering

Maybe, Maybe, yes.
If you are in a school environment in the US, you may have an ad-hoc network blocker doing Denial of Service attacks on your vexnet. This causes lots of red flashing status LEDs. If it works away from school, but not at school, this is likely to cause. Search for “vexnet blocker” in the forum, or for example, see this post:

  1. Our vex net turns orange on the remote when we try to connect it and then it turns red and won’t connect. Sometimes though we get lucky and it does connect and then it disconnects around 2 1/2 minutes later.
  2. We are working on the robot at school but it does have problems connecting when we were working on it at a teammates house as well.
  3. I will try to get a picture of our vex net placement.

Sounds most likely to be a dodgy vexnet key to me.

Try swapping out each one in turn for a known working one if you have one (borrow one from another team to do this if you have no spares) and you should be able to identify which one is causing the problems.

If it is a dodgy battery connection you should be able to tell by wiggling the connector around a bit where it plugs into the cortex. If the power cuts out (cortex lights go off for a short interval) then this may be the problem.

Personally I’ve never found an extension cable to help very much because it tends to have a looser connection into the cortex. There’s plenty more discussion on usb extensions elsewhere on this forum though.