To make your quadruped walk, you will first need to connect the servomotor controller to the servos. The servo controller you are going to use for this project is a simple servomotor controller utilizing USB from Pololu (Pololu item number 1354, available at pololu.com) that can control 18 servomotors. Here is an image of the unit:

Make sure that you order the assembled version. This piece of hardware will turn USB commands from the BeagleBone Black into signals that control your servomotors. Pololu makes a number of different versions of this controller, each able to control a certain number of servos. In this case, you may want to choose the 18-servo version, so you can control all 12 servos with one controller and also add an additional servo to control the direction of a camera or sensor. You could also choose the 12-servo version. One advantage of the 18-servo controller is the ease of connecting power to the unit via screw-type connectors...