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9. Pin Assignment Tables

General features of the Pololu 3pi robot, top view.

Labeled bottom view of the Pololu 3pi robot.

Specific features of the Pololu 3pi robot, top view.

Pin Assignment Table Sorted by Function

Function	Arduino Pin	ATmega168 Pin
free digital I/Os (x3) (remove PC5 jumper to free digital pin 19)	digital pins 0, 1, 19	PD0, PD1, PC5
free analog inputs (if you remove jumpers, x3)	analog inputs 5 – 7	PC5, ADC6, ADC7
motor 1 (left motor) control (A and B)	digital pins 5 and 6	PD5 and PD6
motor 2 (right motor) control (A and B)	digital pins 3 and 11	PD3 and PB3
QTR-RC reflectance sensors (left to right, x5)	digital pins 14 – 18	PC0 – PC4
red (left) user LED	digital pin 1	PD1
green (right) user LED	digital pin 7	PD7
user pushbuttons (left to right, x3)	digital inputs 9, 12, and 13	PB1, PB4, and PB5
buzzer	digital pin 10	PB2
LCD control (RS, R/W, E)	digital pins 2, 8, and 4	PD2, PB0, and PD4
LCD data (4-bit: DB4 – DB7)	digital pins 9, 12, 13, and 7	PB1, PB4, PB5, and PD7
reflectance sensor IR LED control drive low to turn IR LEDs off)	digital pin 19 (through jumper)	PC5
user trimmer potentiometer	analog input 7 (through jumper)	ADC7
2/3rds of battery voltage	analog input 6 (through jumper)	ADC6
ICSP programming lines (x3)	digital pins 11, 12, and 13	PB3, PB4, PB5
reset pushbutton	reset	PC6
UART (RX and TX)	digital pins 0 and 1	PD0 and PD1
I2C/TWI	inaccessable to user
SPI	inaccessable to user

Pin Assignment Table Sorted by Pin

ATmega168 Pin	Orangutan Function	Notes/Alternate Functions
PD0	free digital I/O	USART input pin (RXD)
PD1	free digital I/O	connected to red user LED (high turns LED on) USART output pin (TXD)
PD2	LCD control line RS	external interrupt 0 (INT0)
PD3	M2 control line	Timer2 PWM output B (OC2B)
PD4	LCD control line E	USART external clock input/output (XCK) Timer0 external counter (T0)
PD5	M1 control line	Timer0 PWM output B (OC0B)
PD6	M1 control line	Timer0 PWM output A (OC0A)
PD7	LCD data line DB7	connected to green user LED (high turns LED on)
PB0	LCD control line R/W	Timer1 input capture (ICP1) divided system clock output (CLK0)
PB1	LCD data line DB4	user pushbutton (pressing pulls pin low) Timer1 PWM output A (OC1A)
PB2	buzzer	Timer1 PWM output B (OC1B)
PB3	M2 control line	Timer2 PWM output A (OC2A) ISP programming line
PB4	LCD data line DB5	user pushbutton (pressing pulls pin low) Caution: also an ISP programming line
PB5	LCD data line DB6	user pushbutton (pressing pulls pin low) Caution: also an ISP programming line
PC0	QTR-RC reflectance sensor	(drive high for 10 us, then wait for line input to go low) sensor labeled PC0 (leftmost sensor)
PC1	QTR-RC reflectance sensor	(drive high for 10 us, then wait for line input to go low) sensor labeled PC1
PC2	QTR-RC reflectance sensor	(drive high for 10 us, then wait for line input to go low) sensor labeled PC2 (center sensor)
PC3	QTR-RC reflectance sensor	(drive high for 10 us, then wait for line input to go low) sensor labeled PC3
PC4	QTR-RC reflectance sensor	(drive high for 10 us, then wait for line input to go low) sensor labeled PC4 (rightmost sensor)
PC5	analog input and digital I/O	jumpered to sensors’ IR LEDs (driving low turns off emitters) ADC input channel 5 (ADC5)
ADC6	dedicated analog input	jumpered to 2/3rds of battery voltage ADC input channel 6 (ADC6)
ADC7	dedicated analog input	jumpered to user trimmer potentiometer ADC input channel 7 (ADC7)
reset	reset pushbutton	internally pulled high; active low digital I/O disabled by default