I have connected the RPM_Eng1 Simvim parameter to my 1st gauge (I've print an Airspeed because I initially planned to connect it to Airspeed indicator). It is drived by a X.27 motor/6600controler/Uno slave board. One can see on this video (https://youtu.be/t9WG5YYECbQ) that the gauge resets when I load a new plane. After that, the hand jitters, but it doesn't follow the RPM value when I increase/decrease the RPM.
Maybe it is an issue related to GND, so my question is: which GND pin of the MEGA2560 am I supposed to used to connect my UNO board and my V6600 board to the MEGA2560 board (the ones on "Power group" or the ones near 52/53 digital i/o) ?