Arduino Ports

The Arduino Uno has three I/O ports (B, C and D) that can be used for digital input and output. The bits in the ports are named on the Arduino board with the names that are used in the Arduino IDE application as D0 through D13 and A0 through A5.

In EE109 we don't use the Arduino application for programming and these names are not the names that must be used when writing code to be compiled by the avr-gcc software for downloading to the Arduino. The avr-gcc software uses names that are defined by the manufacturer of the ATmega328P microcontroller IC. The diagram below shows the relationship between the two sets of names.