Arduino Internals

Pin Descriptions

The pins of the device, no matter what the package variation, are the microcontroller’s electrical and mechanical connection to the outside world. Some pins, such as the power supply connections V_CC and ground (GND), have only a single function. Most of the rest of the pins have at least two and sometimes more possible functions. These functions are determined by a combination of device configuration fuse settings and software. See the “Configuration Fuses” section later in this chapter.

Power Pins

The ATmega family runs on direct-current (DC) electrical power, in the range of 1.8V to 5.5V. The higher voltage supplies allow for faster clock rates. See Table 3-1.

Curiously, the ATmega2560 on the Arduino Mega has only a single ...