[DonRotolo]

In the olden days, we'd connect a digital I/O line (on the digital sidecar) to the center pin of the brake/coast 3-pin connector. Setting the pin high yielded one behavior, setting it low yielded the other behavior. I don't remember which was which, but surely you can figure it out in a minute of testing.

Use only the Signal line of the Digital I/O, not the Gnd or +5 pins

Then post the results here for the next guy, OK?