Cortex Microcontroller Questions

We are planning to use the Vexpro CIM motors with the VEX ARM® Cortex®-based Microcontroller and the VEXnet Key 2.0, but we have a few questions.

  1. Are Vexpro motor controllers and motors compatible with the cortex microcontroller?

  2. The stall current of the CIM motors is 131 amps. Will this amount of current damage the cortex?

  3. Is the Vexnet key compatible with any other transmitters or does it only work with the Vex joysticks.

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  1. no
  2. yes
  3. no

If the motor controller has a PWM input (the victor does for example), you will have no trouble controlling it with a cortex. You may need a male to male PWM adapter however.

Usually a motor controller (not the vex MC29) will have a 3 pin PWM cable for control (like the cortex vex cables) - and a second input for main power. The 3 pin cable is just used for signal and not motor power. The 131A you need will have to be provided to the main power and is seperate from the cortex system.


Thanks jacko. We already have a Taranis X7 we use for our drone. I believe it is a PWM. Do you think it will work?

Thanks for your response djavaisadog.

No, VEXnet is proprietary and you can’t use other transmitters with it.

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If you really want to control a CIM with a cortex you need to do this:

  1. you need to get a CIM and a motor controller combo that works with a roborio.

  2. the motor controller needs to have a 3 wire Signal/Power connection

  3. Flash the correct firmware to the motor controllers

  4. Set up a driver program, like any other program, in RobotC (I used this one when doing this a LONG time ago, and it worked well)

  5. Turn on the roborio (FRC side)

  6. Turn on the Cortex side

  7. Viola, you can now control a CIM with a cortex.

My team did this to our 2012 robot, and it still works to this day. I can’t tell you the motor controllers we used. I’m going to go and draw up a diagram real quick to show you the wiring. The basic wiring is wire the robot like you would any other FRC robot, and then chuck in a motor controller with the correct signal port, and the run the signal ports to the cortex.

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As has been stated earlier, you can plug Victor speed controllers straight into a Cortex motor port (ports 2 through 9) and drive a CIM from it, just like you would an MC29 and 393 motor. No difference at all. There is no need for any other devices.
I’ve got a few things made this way.

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