7. AVR Pin Assignment Table Sorted by Pin

Port A Pins Orangutan Function Notes/Alternate Functions
PA0analog input and digital I/OADC input channel 0 (ADC0)
PA1analog input and digital I/OADC input channel 1 (ADC1)
PA2analog input and digital I/OADC input channel 2 (ADC2)
PA3analog input and digital I/OADC input channel 3 (ADC3)
PA4analog input and digital I/OADC input channel 4 (ADC4)
PA5analog input and digital I/OADC input channel 5 (ADC5)
PA6analog input and digital I/OADC input channel 6 (ADC6)
PA7analog input and digital I/OADC input channel 7 (ADC7)
Port B Pins Orangutan Function Notes/Alternate Functions
PB1LCD control line R/WDivided system clock output (CLKO)
Timer/Counter 1 External Counter Input (T1)
PB2LCD control line EExternal interrupt 2 (INT2)
Analog Comparator Positive Input (AIN0)
PB3digital I/OTimer0 PWM output A (OC0A)
Analog Comparator Negative Input (AIN1)
PB4digital output*Timer0 PWM output B (OC0B)
SPI Slave Select Input (SS)
PB5auxiliary processor control lineSPI Master Output/Slave Input (MOSI)
ISP programming line
PB6auxiliary processor control lineSPI Master Input/Slave Output (MISO)
ISP programming line
PB7auxiliary processor control lineSPI Clock (SCK)
ISP programming line
Port C Pins Orangutan Function Notes/Alternate Functions
PC0digital I/OI2C/TWI clock line (SCL)
PC1digital I/OI2C/TWI input/output data line (SDA)
PC2LCD data line DB4user pushbutton (pressing pulls low)
PC3LCD data line DB5user pushbutton (pressing pulls low)
PC4LCD data line DB6green user LED (high turns LED on)
PC5LCD data line DB7user pushbutton (pressing pulls low)
PC6M2 direction control line
PC7M1 direction control line
Port D Pins Orangutan Function Notes/Alternate Functions
PD0digital I/OUSART0 input pin (RXD0)
PD1digital I/Ored user LED
(low turns LED on; connection
can be cut and replaced with jumper)
USART0 output pin (TXD0)
PD2digital I/OUSART1 input pin (RXD1)
External interrupt 0 (INT0)
PD3digital I/OUSART1 output pin (TXD1)
External interrupt 1 (INT1)
PD4buzzerTimer1 PWM output B (OC1B)
PD5digital I/Oservo pulse output (SPWM)
Timer1 PWM output A (OC1A)
PD6M2 speed control lineTimer2 PWM output B (OC2B)
PD7M1 speed control lineTimer2 PWM output A (OC2A)
Misc. Pins Orangutan Function Notes/Alternate Functions
AREFADC reference pin
AVCCsupply voltage for Port A and ADCnot accessible to the user
RESETReset inputreset button (pressing resets MCU)
XTAL120 MHz resonator inputnot accessible to the user
XTAL220 MHz resonator inputnot accessible to the user

*: Using PB4/SS as an input will interfere with communication to the auxiliary processor, so we recommend using it as a digital output. See Section 3.j of the Pololu USB AVR C/C++ User’s Guide for more information.