To avoid ground loops and for other reasons as well I want to power my arduino from the Dual G2 High-Power Motor Driver shield. However, I saw some warnings at Pololu for other shields about connecting the USB cable when the arduino is powered from the shield because it means that power is coming from two different places. On the other hand the arduino is suppose to take the power from vin if available. So my question is: Can I power my arduino from the motor shield and still connect the arduino to my PC when programming the arduino? I know this question has been discussed before but the information available is unfortunately not clear to me. Of course, I can turn of the power to the shield when programming the arduino but it is just a matter of time when I forget.
Hi.
Connecting USB while the Arduino Mega is powered through the G2 high-power motor driver shield should be as safe as connecting it while the Arduino Mega is powered through its power jack. There is a flaw in the Arduino’s power circuit design that allows some current to flow back into the USB port under certain conditions, which you can read more about in this thread, so we recommend avoiding it.
-Claire