Hi yes maybe I did not phrase that correctly!! Gee you were quick to step in Alan hehe
On the controller, TX is not connected on any I have seen.
I say TX in the previous post - meaning the signal coming from the USB cable.
The newer MP boards with reverse enabled have a wire bridge across (d) and (rx) on the controller.
With power connected to the Pie, and no errors, by dropping (rx) to ground, connected to (d) enables reverse.
As you do not have power connected with the USB settings, (rx) is used for comms.
Some other posts I've read elsewhere is that its bi-directional coming from the (rx) pin only.
I can confirm this because I replaced my internal controller on the rear wheel, only connecting (rx) and leaving (d) alone as I don't need reverse. (tx) is not connected.
Anyway long story short if you want to connect the wires to the controller for a USB cable its:
YELLOW (rx)
GREEN (cruise)
Black (GND)
Red (5v)
I did it last night
I'm still not 100% if it transmits via the cruise control port - from what I've experienced it's a high low signal driven by the controller to feed to the USB-connector circuit to enable to 'listen' for data.
MM