pwm_test.zip_linux pwm_pwm_pwm linux

#include <stdio.h> #include <termios.h> #include <unistd.h> #include <stdlib.h> #define PWM_IOCTL_SET_FREQ 1 #define PWM_IOCTL_STOP 0 #define ESC_KEY 0x1b static int getch(void) { struct termios oldt,newt; int ch; if (!isatty(STDIN_FILENO)) { fprintf(stderr, "this problem should be run at a terminal\n"); exit(1); } // save terminal setting if(tcgetattr(STDIN_FILENO, &oldt) < 0) { perror("save the terminal setting"); exit(1); } // set terminal as need newt = oldt; newt.c_lflag &= ~( ICANON | ECHO ); if(tcsetattr(STDIN_FILENO,TCSANOW, &newt) < 0) { perror("set terminal"); exit(1); } ch = getchar(); // restore termial setting if(tcsetattr(STDIN_FILENO,TCSANOW,&oldt) < 0) { perror("restore the termial setting"); exit(1); } return ch; } static int fd = -1; static void close_buzzer(void); static void open_buzzer(void) { fd = open("/dev/pwm", 0); if (fd < 0) { perror("open pwm_buzzer device"); exit(1); } // any function exit call will stop the buzzer atexit(close_buzzer); } static void close_buzzer(void) { if (fd >= 0) { ioctl(fd, PWM_IOCTL_STOP); close(fd); fd = -1; } } static void set_buzzer_freq(int freq) { // this IOCTL command is the key to set frequency int ret = ioctl(fd, PWM_IOCTL_SET_FREQ, freq); if(ret < 0) { perror("set the frequency of the buzzer"); exit(1); } } static void stop_buzzer(void) { int ret = ioctl(fd, PWM_IOCTL_STOP); if(ret < 0) { perror("stop the buzzer"); exit(1); } } int main(int argc, char **argv) { int freq = 1000 ; open_buzzer(); printf( "\nBUZZER TEST ( PWM Control )\n" ); printf( "Press +/- to increase/reduce the frequency of the BUZZER\n" ) ; printf( "Press 'ESC' key to Exit this program\n\n" ); while( 1 ) { int key; set_buzzer_freq(freq); printf( "\tFreq = %d\n", freq ); key = getch(); switch(key) { case '+': if( freq < 20000 ) freq += 10; break; case '-': if( freq > 11 ) freq -= 10 ; break; case ESC_KEY: case EOF: stop_buzzer(); exit(0); default: break; } } }