In the process of improving the soldering work on Digital I/O from pin 8-13, I suddenly discovered that my two wires 1 to pin2 and the other to pin 13 were soldered in the wrong places. I soldered on the second row, right underneath of the top row. I soldered onto pin 13 and pin 2, and guess what, the voltage between two terminals swings, and the same for all other motor terminals. Now the motor rotates forward and backward for all 4 posts!! Thank you so much for your patience, and your troubleshooting skills. I am very impressed by your hard and effective work, and the best customer support I have ever experienced!!