Cortex V4 and controllers

during my teams last tournament, about half way through the match, our controllers would stop working; mainly aour driving, which was directly connected into the field and had the USB key. Does anyone have any ideas as to why this might happen?

What did the status lights on your controller show? Without knowing the status of your lights, I would say that the most likely causes were:

  1. Loose main battery connector (probably with no or dead backup battery).

  2. Low or dead batteries in the transmitter.

  3. Overdriven motors that went to sleep to recover. (I’ve never seen so many over-geared robots as I’ve seen this year. I think many people assume the 393 motors are magical and not subject to the laws of physics.)

  4. Software flaws.

  5. Bad cable from the transmitter to the field.

Problems I can pretty much guarantee you aren’t having:

  1. The field control system turning your robot off.

The last #1 looks much like #5 (and I perceive #5 to be common), yet field managers say they can monitor the system and ‘know/guarantee’ it is not the field control system. How does that work, and why can’t it detect bad cables as well?

With Crystals, it was recommended to unplug the field cable during driver period if you thought you were disabled. If it still doesn’t work, its your own problem.

Is the same true for Vexnet field control system also?

This also happened to my team , 569C , at a tournament and sometimes we were unable to drive for a few seconds and other times the whole match. It finally got fixed when we got picked in the quarter finals but we had no idea what happened.

You look at the GAME LED on the VEXnet Transmitter Upgrade module or VEXnet Joystick. If the GAME LED is correct, then your transmitter has the correct signal.

Unplugging the competition cable in the middle of a match shouldn’t be necessary with the various LEDs that are on the transmitter/joystick. Look at the VEXnet LED Patterns document ( for the LED codes from the VEXnet Transmitter Upgrade and see page 8 of the Cortex user guide ( for the LED patterns on the VEXnet joystick. Those two documents were really helpful at the tournament we ran on Dec. 4. for the LED patterns on the VEXnet joystick. Those two documents were really helpful at the tournament we ran on Dec. 4.)

  1. vex never follows the laws of physics anyways :stuck_out_tongue:
  2. i think its because many people think that “if four 3-wire motors can drive my robot 1:1, then four HS motors torqued up can drive my robot 2:1!”
    (which SHOULD make sense except they didn’t calculate in the acceleration…)

Except the problem has nothing to do with acceleration at all.

(and in theory if the HSMs were actually “twice as powerful” they WOULD accelerate twice as fast)