Pololu 3pi Robot - Manual (Page 26)

if(counter < 20 || counter >= 60)
set_motors(40,-40);
else
set_motors(-40,40);
// This function records a set of sensor readings and keeps
// track of the minimum and maximum values encountered. The
// IR_EMITTERS_ON argument means that the IR LEDs will be
// turned on during the reading, which is usually what you
// want.
calibrate_line_sensors(IR_EMITTERS_ON);
// Since our counter runs to 80, the total delay will be
// 80*20 = 1600 ms.
delay_ms(20);
}
set_motors(0,0);
// Display calibrated values as a bar graph.
while(!button_is_pressed(BUTTON_B))
{
// Read the sensor values and get the position measurement.
unsigned int position = read_line(sensors,IR_EMITTERS_ON);
// Display the position measurement, which will go from 0
// (when the leftmost sensor is over the line) to 4000 (when
// the rightmost sensor is over the line) on the 3pi, along
// with a bar graph of the sensor readings. This allows you
// to make sure the robot is ready to go.
clear();
print_long(position);
lcd_goto_xy(0,1);
display_readings(sensors);
delay_ms(100);
}
wait_for_button_release(BUTTON_B);
clear();
print("Go!");
// Play music and wait for it to finish before we start driving.
play_from_program_space(go);
while(is_playing());
}
// This is the main function, where the code starts. All C programs
// must have a main() function defined somewhere.
int main()
{
unsigned int sensors[5]; // an array to hold sensor values
// set up the 3pi
initialize();
// This is the "main loop" - it will run forever.
while(1)
{
// Get the position of the line. Note that we *must* provide
// the "sensors" argument to read_line() here, even though we
// are not interested in the individual sensor readings.
unsigned int position = read_line(sensors,IR_EMITTERS_ON);
if(position < 1000)
{
// We are far to the right of the line: turn left.
// Set the right motor to 100 and the left motor to zero,
// to do a sharp turn to the left. Note that the maximum
// value of either motor speed is 255, so we are driving
// it at just about 40% of the max.
set_motors(0,100);
// Just for fun, indicate the direction we are turning on
// the LEDs.
left_led(1);
Pololu 3pi Robot User's Guide © 2001–2014 Pololu Corporation
7. Example Project #1: Line Following Page 26 of 63