alarm: Add first rough implementation

main/CMakeLists.txt

@@ -1,2 +1,2 @@
-idf_component_register(SRCS "esp32_alarm_clock_main.c" "wifi.c" "storage.c" "api.c" "ds3231.c" "bcd.c" "tm1637.c" "time_sync.c" "time_display.c"
+idf_component_register(SRCS "esp32_alarm_clock_main.c" "wifi.c" "storage.c" "api.c" "ds3231.c" "bcd.c" "tm1637.c" "time_sync.c" "time_display.c" "alarm.c"
                     INCLUDE_DIRS "")

main/alarm.c

@@ -0,0 +1,50 @@
+/*
+ * 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));
+}

main/alarm.h

@@ -0,0 +1,8 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Helmut Pozimski <helmut@pozimski.eu>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+void alarm_init(uint32_t frequency);
+void beep(uint32_t length_ms);