esp32-alarm-clock/main/alarm.c

/*
 * SPDX-FileCopyrightText: 2023 Helmut Pozimski <helmut@pozimski.eu>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 */

#include <driver/ledc.h>
#include <esp_err.h>
#include <freertos/FreeRTOS.h>
#include <freertos/event_groups.h>

#define MODE LEDC_LOW_SPEED_MODE
#define CHANNEL LEDC_CHANNEL_0
#define DUTY 4095

/* TODO: This code works reasonably well for low frequencies
 * but has nasty high-pitched interference for high frequencies.
 * It needs to be checked if this is caused by the code or the
 * circutry.
 */

void alarm_init(uint32_t frequency) {
	 ledc_timer_config_t ledc_timer = {
    	.speed_mode       = MODE,
      .timer_num        = LEDC_TIMER_0,
      .duty_resolution  = LEDC_TIMER_13_BIT,
      .freq_hz          = frequency,  // Set output frequency at 5 kHz
      .clk_cfg          = LEDC_AUTO_CLK
    };
    ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));

 	ledc_channel_config_t ledc_channel = {
   	.speed_mode     = MODE,
      .channel        = CHANNEL,
      .timer_sel      = LEDC_TIMER_0,
      .intr_type      = LEDC_INTR_DISABLE,
      .gpio_num       = 5,
      .duty           = 0,
      .hpoint         = 0
	};
   ESP_ERROR_CHECK(ledc_channel_config(&ledc_channel));
}

void beep(uint32_t length_ms) {
	ESP_ERROR_CHECK(ledc_set_duty(MODE, CHANNEL, DUTY));
	ESP_ERROR_CHECK(ledc_update_duty(MODE, CHANNEL));
	vTaskDelay(length_ms / portTICK_PERIOD_MS);
	ESP_ERROR_CHECK(ledc_set_duty(MODE, CHANNEL, 0));
	ESP_ERROR_CHECK(ledc_update_duty(MODE, CHANNEL));
}