// Listing 6-17: /chp06/wiringPi/servo.cpp
#include <iostream>
#include <wiringPi.h>
#include <unistd.h>
using namespace std;
#define PWM_SERVO 18 // this is PWM0, Pin 12
#define BUTTON_GPIO 27 // this is GPIO27, Pin 13
#define LEFT 29 // manually calibrated values
#define RIGHT 118 // for the left, right and
#define CENTER 73 // center servo positions
bool sweeping = true; // sweep servo until button pressed
void buttonPress(void) { // ISR on button press - not debounced
cout << "Button was pressed -- finishing sweep." << endl;
sweeping = false; // the while() loop should end soon
}
int main() { // must be run as root
wiringPiSetupGpio(); // use the GPIO numbering
pinMode(PWM_SERVO, PWM_OUTPUT); // the PWM servo
pinMode(BUTTON_GPIO, INPUT); // the button input
wiringPiISR(BUTTON_GPIO, INT_EDGE_RISING, &buttonPress);
pwmSetMode(PWM_MODE_MS); // use a fixed frequency
pwmSetRange(1000); // 1000 steps
pwmSetClock(384); // gives 50Hz precisely
cout << "Sweeping the servo until the button is pressed" << endl;
while(sweeping) {
for(int i=LEFT; i<RIGHT; i++) { // rotate to right
pwmWrite(PWM_SERVO, i);
usleep(10000);
}
for(int i=RIGHT; i>=LEFT; i--) { // rotate to left
pwmWrite(PWM_SERVO, i);
usleep(10000);
}
}
pwmWrite(PWM_SERVO, CENTER); // rotate to center
cout << "Program has finished gracefully - servo centred" << endl;
return 0;
}