Unlike previous steps, we will be making some small modifications to an Arduino shield. Our motor shield uses pins 11 through 13, but the Raspberry Pi already has these pins set aside for SPI. This means that we will need to disable some of the current pins on the motor shield. You will also need to use your flathead screwdriver for some of these steps:
Unplug the red, black, and yellow wires that connect your breadboard to the Raspberry Pi to Arduino shield.
Bend the metal legs on digital pins numbered 4, 5, 6, 11, 12, and 13. You do not need to remove the legs; just ensure that they will not connect with the header on the bridge shield.
You can connect the motor shield to the Raspberry Pi to Arduino shield. We will now run some jumper wires to connect digital pins 11, 12, and 13 on the motor shield to digital pins 4, 5, and 6 on the Raspberry Pi to Arduino shield, respectively. Take your jumper wires and connect 11 to 4, 12 to 5, and 13 to 6.
Our two shields...