The raw Servo42c library is available here:

https://github.com/G-EDM/SERVO42C-ESP32WROOM32-UART-Library

The library is written for the newer v1.1 version and does not support the v1.0 version. 

This one maps GPIO0 and GPIO 16 to UART2. Gpio16 is RX and GPIO0 is used a TX.

Connecting the driver is easy and requires only four wires.

RX, TX, 12v+, 12v- (ESP RX goes to 42C TX and ESP TX to 42C RX)

The GND of the 12v PSU needs to be shared with the ESP GND. The G-EDM motionboard is powered with a 12v PSU and already has a shared gnd.

The Motionboard has GPIO0 and GPIO16 exposed ont he PCB but so far they where just not used. Soldering a little JST connector on the board and it it good to go. The 12v comes from the PSU that powers the board. Currently it just writes all the hardcoded default configurations onto the 42C driver on boot to get some low tensions etc.