The recommended C11 BOB has two power inputs. One for the computer side and one for the machine side. Using separate power supplies helps isolate the computer from the machine. Mine came with a USB power cord for the computer side which gets 5 V DC from the USB port. Or you can use any standard 5 V DC regulator. The machine side is powered by the 5 V supply on the main power supply. Or you can use any standard 5 V DC regulator. We want pins 10 and 11 to have pull-up resistors. The C11 BOB has jumpers for that. Or you have to run a 4.7k ohm resistor from each pin to 5 V. We want LEDs to see what's going on. The C11 BOB has LEDs on every pin. Otherwise, a good way to test 5V logic is to use an LED with internal resistor, or else you have to use a regular LED with a resistor in series. Connect the LEDs from the pin to ground. The C11 BOB requires a jumper from 5 V to EN, the enable pin.