pwm.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*1c6*/
#define PWM_PATH "/sys/class/pwm/pwmchip10"
#define PERIOD_NS 1000000
#define MIN_DUTY_CYCLE_NS 0
#define MAX_DUTY_CYCLE_NS 1000000

int main()
{
	FILE *pwm_export = fopen(PWM_PATH "/export", "w");
	if (!pwm_export) {
		perror("Failed to open PWM export");
		return 1;
	}
	fprintf(pwm_export, "0");
	fclose(pwm_export);

	FILE *period_file = fopen(PWM_PATH "/pwm0/period", "w");
	if (!period_file) {
		perror("Failed to open PWM period");
		return 1;
	}
	fprintf(period_file, "%d", PERIOD_NS);
	fclose(period_file);

	FILE *enable_file = fopen(PWM_PATH "/pwm0/enable", "w");
	if (!enable_file) {
		perror("Failed to open PWM enable");
		return 1;
	}
	fprintf(enable_file, "1");
	fclose(enable_file);

	int direction = 1; 
	int duty_cycle_ns = 0;

	while (1) {
		duty_cycle_ns += 10000 * direction;
		if(duty_cycle_ns == MAX_DUTY_CYCLE_NS)
			direction = -1;
		else if(duty_cycle_ns == MIN_DUTY_CYCLE_NS)
			direction = 1; 

		FILE *duty_cycle_file = fopen(PWM_PATH "/pwm0/duty_cycle", "w");
		if (!duty_cycle_file) {
			perror("Failed to open PWM duty cycle");
			return 1;
		}
		fprintf(duty_cycle_file, "%d", duty_cycle_ns);
		fclose(duty_cycle_file);

		usleep(50000); 
	}

	FILE *pwm_unexport = fopen(PWM_PATH "/unexport", "w");
	if (!pwm_unexport) {
		perror("Failed to open PWM unexport");
		return 1;
	}
	fprintf(pwm_unexport, "0");
	fclose(pwm_unexport);

	return 0;
}