There was another problem occur during wiring connection. At first, I use a micro USB cable through Pi3 to power up the PXFmini. All of the motors is connected to the input pins, however, only servos work but the DC motor won't work.
I reckon it is because of the power supply which the DC motor require 7.3V but micro USB feed only 5.3V. Or there is some other factor I do not know.
I also tried connecting it using my existing power module, in the picture
But, this time it never powering up the PXFmini or Pi3, but power up the ESC instead.
My questions are,
1. Is it the matter of not enough power from micro USB through Pi3 for the DC motor's ESC?
2. Do I have to plug in both power module and micro USB? Or I need only one way or another?
3. Is my power module valid for the PXFmini? Why can't I power up the PXFmini using only power module.