CAN bus port minus the voltage pin
Info here
All In One Schematic / Diagrams
and here
the 1, 2, 3 and 4 are channels. I think channel 2 is the trigger but just swap around until it shows up in the VESC tool when you run the input wizard. You will need to bind it and set the failsafe first (that’s what the black jumper plugged into channel 4 in that picture is)
The metr website shows what pins are what. Everything matches the ESC except the TX and RX.
3.3v → 3.3v
gnd → gnd
tx → rx
rx → tx
You can ignore the swd and swc pins. I believe those are for programming the firmware onto the metr.