Not sure if this is specifically answering the question, but one thing that has helped my team with dodgy WiFi keys is zip-tieing them to the micro controller using large zip ties. This prevents keys from wobbling out of their proper positions.
Getting connected is key to staying connected (in my opinion). I’ve found that when you’re having connection issues, it’s best to unplug all of the robot batteries and turn off the joystick. Then power everything back on… That’s the only real VEXnet “trick” I’ve learned…
One other thing: I’ve noticed that if the remote disconnects during a match, lifting it up high can make it connect faster…
Also, some basic key positioning rules should be followed, i.e. don’t snuggle your key up to a large amount of metal, that also bugger with the WiFi sometimes. Using USB extenders can solve this problem if your microcontroller is close to a large amount of metal.
Obviously VEX robots are mostly metal, but try to position your key so that it has a some sort of airspace between it and your controller.
First, you should make sure that you test your VexNet keys to make sure they work because some of ours didn’t work so we did extremely badly in one competition. Isolate the bad ones and label them so that you don’t use them and carry some spares with you if you have any to your competition or borrow one from another team.
Second, make sure your battery is securely connected and you have a backup battery that still has power because usually our problems are caused by accidentally jostling the battery and then we lose power for the rest of the match.
Third, as many people have said, try positioning your cortex so that there is no metal directly covering the vex net key.
Fourth, make sure that you have updated to the current VexNet firmware.
That’s about all the most common problems. There are some problems with current RobotC master firmware so if you have more problems, consider staying with 3.04 or same with EasyC because RobotC 3.04 is incredibly reliable.
I am assuming you’re talking about connecting to a VEXnet connection at an event and not just everyday classroom.
At a competition:
Make sure the 9V battery is reading at least 8.6V when the robot is turned on. If the voltage is much lower it will affect the connection with the field at times. (I don’t know why, but it’s the battle proven theory).
Make sure all mastercodes are on the same version.
Make sure the keys work properly off field first Big one When you plug into the field, pick up the wire that plugs into the controller, touch your hand to the tower, then plug it into the remote. This will get ride of any static electricity. (Battle proven theory)
Make sure data is turned off on smartphones and tablets within a decent radius of the field.
The one that normally bites us in the butt is the 9V being charged enough, it’s one of those things that you tend to forget about but it can easily cost you a match.
The theory I have heard about the 9V is that when VEXnet makes the initial connection it puts a giant load on the power system of the controller and can cause it to drop signal if not enough instantaneous power is available. By no means am I an electrical guy, so I can’t tell you any specific details.
The 9V battery only provides power if the main 7.2V NiMH battery voltage drops in situations such as when motors stall. There is some information in this thread in post #15 onwards. The NiMH has a huge capacity compared to the 9V backup and will have no problems with the WiFi power, one 269 motor stalled will draw more than 4 times the current of the WiFi. Bear in mind the WiFi uses a USB connection, USB can supply at most 500mA at 5V so the WiFi uses a maximum of 2.5W, not very much.