Sorry,我可能解釋的不清楚,請參考如下:
如果要共地,需將Channel"s GND connect to MPC508"s GND,
But the module do not supply MPC508"s GND on terminal of
the module,it only supply GND of the power. And the GND of
Power is not MPC508"s GND. You need to open the shell of the
module and modify the circuit on 7017"s PCB. So it is
difficult and instable.