We have been having VEXNet connection problems. We can walk around the perimeter of the field and see the VEXNet LED flash red or occasionally go red for several seconds. We found that we could resolve the problem by putting the VEXNet key on a USB extension cable (Male-A to Female-A).
There are several threads that blame this type of problem on thermal issues. I believe that what we are seeing is more likely to be a RFI issue.
To check for thermal or battery problems, we installed a freshly charged battery (the new kind) in a robot that had not been powered on for 4 day. With the key in the Cortex, we had communications problems within 30 seconds. We put the key on the extension cable and operated with no problems. Also, while the key was on the cable, we used a heat gun on the key. It was just short of too hot to touch (my cost, if we toasted it). We did not have any problems while the key was hot.
When the key is in the Cortex, it is partially covered by a flat plate that could be blocking some signal. With the key on the extension cable, we put the key completely under the plate and operated with no problems.
We replaced the key with a spare one. Installed in the Cortex, it failed immediately. Installed on the cable, it operated correctly.
We connected the key to the cable and placed it on the Cortex as close to the original position as possible. We operated with no problems.
Is it permissible to use an USB extension cable to try to alleviate these problems?
We have ordered 10 six inch and 10 one meter cables that we will share with other teams at the Pan Pacific competition next weekend if the cables are allowed.