samples/basic/blinky_pwm/src/main.c

/*
 * Copyright (c) 2016 Intel Corporation
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @file Sample app to demonstrate PWM.
 */

#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>
#include <zephyr/device.h>
#include <zephyr/drivers/pwm.h>

static const struct pwm_dt_spec pwm_led0 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led0));

#define MIN_PERIOD PWM_SEC(1U) / 128U
#define MAX_PERIOD PWM_SEC(1U)

void main(void)
{
	uint32_t max_period;
	uint32_t period;
	uint8_t dir = 0U;
	int ret;

	printk("PWM-based blinky\n");

	if (!device_is_ready(pwm_led0.dev)) {
		printk("Error: PWM device %s is not ready\n",
		       pwm_led0.dev->name);
		return;
	}

	/*
	 * In case the default MAX_PERIOD value cannot be set for
	 * some PWM hardware, decrease its value until it can.
	 *
	 * Keep its value at least MIN_PERIOD * 4 to make sure
	 * the sample changes frequency at least once.
	 */
	printk("Calibrating for channel %d...\n", pwm_led0.channel);
	max_period = MAX_PERIOD;
	while (pwm_set_dt(&pwm_led0, max_period, max_period / 2U)) {
		max_period /= 2U;
		if (max_period < (4U * MIN_PERIOD)) {
			printk("Error: PWM device "
			       "does not support a period at least %lu\n",
			       4U * MIN_PERIOD);
			return;
		}
	}

	printk("Done calibrating; maximum/minimum periods %u/%lu usec\n",
	       max_period, MIN_PERIOD);

	period = max_period;
	while (1) {
		ret = pwm_set_dt(&pwm_led0, period, period / 2U);
		if (ret) {
			printk("Error %d: failed to set pulse width\n", ret);
			return;
		}

		period = dir ? (period * 2U) : (period / 2U);
		if (period > max_period) {
			period = max_period / 2U;
			dir = 0U;
		} else if (period < MIN_PERIOD) {
			period = MIN_PERIOD * 2U;
			dir = 1U;
		}

		k_sleep(K_SECONDS(4U));
	}
}