Updated motor controllers with DC braking

I’d like to see the Vex motor controllers upgraded to support dynamic braking under program control. This would help prevent back-driving without requiring a full control loop to actively maintain a fixed position (see this thread for an example).

The Motor Controller 29 firmware could watch for a specific signal that isn’t a valid R/C pulse train (say, 50% duty cycle?) and enable DC braking.

It may already be electrically possible for the Cortex’s built-in 2-wire ports to do this with just a firmware upgrade, if there isn’t a lockout that prevents both halves of the H-bridge both from switching to the same rail.

In order to use this feature in software, there would have to be a new function added, since it doesn’t really fit anywhere on the -128…127 power spectrum already available.


  • Dean

This already exists its just not supported by any of the programming options.

we played around with it by plugging it into an Arduino and then sending a 200us single and sure enough the motors went into a “braking” mode
I think that if it was supported it would almost entirely eliminate the need for arm “reverses” and such.
goes to RobotC feature request thread


Huh - I guess I need to read the product page (which I even linked to!) more thoroughly next time.

I agree that this should go to ROBOTC and EasyC as an enhancement request.


  • Dean

If, as we suspect, the NXP supervisor processor controls the motors then it may also require a firmware upgrade from IFI.