Hello.
If your sensor board draws power from the VIN pin and you have the jumper connected on the MC33926 shield, you should make sure that the voltage of your power supply is within the specifications of your sensor shield. However, if the shield gets power from either the 5V or 3.3V pin, no special considerations are needed. Please note, when stacking multiple shields, you should make sure there are no conflicts between the pins they use. You can find a full list of pins the MC33926 shield uses in the “Shield Connections: Signals, Power, and Motors” section of the dual MC33926 motor driver shield user’s guide.
As for connecting your Arduino to a PC through USB while having the shorting block connected, (assuming you are supplying the shield with an appropriate voltage) it is the same as powering the Arduino through its DC power jack while USB is connected. Arduino intends for this to work, but we generally do not recommend doing so for the reasons mentioned in this thread.
- Jeremy