Once the coding was completed for our Mastermind game we just needed to create two circuits: one for the serial communication between TeraTerm and the A3BU, and one to power the LEDs. The communication circuit was the same MAX232 circuit that was used in previous labs, and can be seen on the left side of the breadboard in the picture below. The circuit to power the LEDs we designed ourselves, and can be seen on the right side of the breadboard.
The LED circuit required several components for each LED leg, including a 1K resistor to moderate the current, and a transistor to provide ground.
In our circuit, the LED leg went to the collector of the transistor, and the emitter of the transistor went to ground. Then the outputs from the A3BU (labeled as inputs in the diagram below because we were viewing them as inputs to the transistor, but they are still output pins) would go to the base of the transistor in order to power the leg of the LED and turn it a certain color.