Another option for user input is to use the ADC to read the position of a potentiometer. Let's revisit some of the things you learned in Chapter 4, PWM and ADC Subsystems, to make our program a bit more interesting.

For this circuit, you will need:

Put it all together on your breadboard, as shown in the figure:

This circuit might look a lot more complicated than what we've done so far, but really it's just a combination of a few of the earlier circuits. The only difference is the configuration of the op-amp.

Here it is being used to buffer the output of a 2:1 voltage divider across the 3.3 V rail, which creates a 1.65 V reference voltage. Let's take a look at the following diagram:

This 1.65 V reference is then being used by the two potentiometers...