Arduino: A Quick-Start Guide, 2nd Edition

Building a Digital-to-Analog Converter (DAC)

The Arduino doesn’t natively support analog output signals, so we need to find a way around this limitation. The solution is a digital-to-analog converter (DAC).^[77] As the name suggests, such a circuit turns a digital input into an analog output. You can find DACs in a lot of consumer devices—for example, in your MP3 player. It turns your digitally encoded music into an analog sound wave.

One of the most important characteristics of a DAC is its resolution. In our case we need to generate four different voltage levels to create a video signal. To encode four voltage levels, we need two bits—that is, our DAC has a 2-bit resolution. The following table shows how we could map the four binary input ...