Arduino Cookbook, 3rd Edition

Digital and Analog Pins

Tables F-1 and F-2 show the digital and analog pins for the Arduino Uno board and the Mega board. The “Arduino” column is for the ATmega168/328, and the “Mega” column is for the ATmega1280/2560.

The Port column lists the physical port used for the pin—see Recipe 18.11 for information on how to set a pin by writing directly to a port. The introduction to Chapter 18 contains more details on timer usage. The table shows:

• USART RX is hardware serial receive

• USART TX is hardware serial transmit

• Ext Int is external interrupt (followed by the interrupt number)

• PWM TnA/B is the Pulse Width Modulation (analogWrite) output on timer n

• MISO, MOSI, SCK, and SS are SPI control signals

• SDA and SCL are I2C control signals

Analog and digital pin assignments common to popular Arduino boards

Arduino 168/328			Arduino Mega (pins 0–19)
Digital pin	Port	Analog pin	Usage	Port	Analog pin	Usage
0	PD 0		USART RX	PE 0		USART0 RX, Pin Int 8
1	PD 1		USART TX	PE 1		USART0 TX
2	PD 2		Ext Int 0	PE 4		PWM T3B, INT4
3	PD 3		PWM T2B, Ext Int 1	PE 5		PWM T3C, INT5
4	PD 4			PG 5		PWM T0B
5	PD 5		PWM T0B	PE 3		PWM T3A
6	PD 6		PWM T0A	PH 3		PWM T4A
7	PD 7			PH 4		PWM T4B
8	PB 0		Input capture	PH 5		PWM T4C
9	PB 1		PWM T1A	PH 6		PWM T2B
10	PB 2		PWM T1B, SS	PB 4		PWM T2A, Pin Int 4
11	PB 3		PWM T2A, MOSI	PB 5