examples: add esp_timer example

examples/system/esp_timer/main/esp_timer_example_main.c

@@ -0,0 +1,100 @@
+/* esp_timer (high resolution timer) example
+
+   This example code is in the Public Domain (or CC0 licensed, at your option.)
+
+   Unless required by applicable law or agreed to in writing, this
+   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+   CONDITIONS OF ANY KIND, either express or implied.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include "esp_timer.h"
+#include "esp_log.h"
+#include "esp_sleep.h"
+#include "sdkconfig.h"
+
+static void periodic_timer_callback(void* arg);
+static void oneshot_timer_callback(void* arg);
+
+static const char* TAG = "example";
+
+void app_main()
+{
+    /* Create two timers:
+     * 1. a periodic timer which will run every 0.5s, and print a message
+     * 2. a one-shot timer which will fire after 5s, and re-start periodic
+     *    timer with period of 1s.
+     */
+
+    const esp_timer_create_args_t periodic_timer_args = {
+            .callback = &periodic_timer_callback,
+            /* name is optional, but may help identify the timer when debugging */
+            .name = "periodic"
+    };
+
+    esp_timer_handle_t periodic_timer;
+    ESP_ERROR_CHECK(esp_timer_create(&periodic_timer_args, &periodic_timer));
+    /* The timer has been created but is not running yet */
+
+    const esp_timer_create_args_t oneshot_timer_args = {
+            .callback = &oneshot_timer_callback,
+            /* argument specified here will be passed to timer callback function */
+            .arg = (void*) periodic_timer,
+            .name = "one-shot"
+    };
+    esp_timer_handle_t oneshot_timer;
+    ESP_ERROR_CHECK(esp_timer_create(&oneshot_timer_args, &oneshot_timer));
+
+    /* Start the timers */
+    ESP_ERROR_CHECK(esp_timer_start_periodic(periodic_timer, 500000));
+    ESP_ERROR_CHECK(esp_timer_start_once(oneshot_timer, 5000000));
+    ESP_LOGI(TAG, "Started timers, time since boot: %lld us", esp_timer_get_time());
+
+    /* Print debugging information about timers to console every 2 seconds */
+    for (int i = 0; i < 5; ++i) {
+        ESP_ERROR_CHECK(esp_timer_dump(stdout));
+        usleep(2000000);
+    }
+
+    /* Timekeeping continues in light sleep, and timers are scheduled
+     * correctly after light sleep.
+     */
+    ESP_LOGI(TAG, "Entering light sleep for 0.5s, time since boot: %lld us",
+            esp_timer_get_time());
+
+    ESP_ERROR_CHECK(esp_sleep_enable_timer_wakeup(500000));
+    esp_light_sleep_start();
+
+    ESP_LOGI(TAG, "Woke up from light sleep, time since boot: %lld us",
+                esp_timer_get_time());
+
+    /* Let the timer run for a little bit more */
+    usleep(2000000);
+
+    /* Clean up and finish the example */
+    ESP_ERROR_CHECK(esp_timer_stop(periodic_timer));
+    ESP_ERROR_CHECK(esp_timer_delete(periodic_timer));
+    ESP_ERROR_CHECK(esp_timer_delete(oneshot_timer));
+    ESP_LOGI(TAG, "Stopped and deleted timers");
+}
+
+static void periodic_timer_callback(void* arg)
+{
+    int64_t time_since_boot = esp_timer_get_time();
+    ESP_LOGI(TAG, "Periodic timer called, time since boot: %lld us", time_since_boot);
+}
+
+static void oneshot_timer_callback(void* arg)
+{
+    int64_t time_since_boot = esp_timer_get_time();
+    ESP_LOGI(TAG, "One-shot timer called, time since boot: %lld us", time_since_boot);
+    esp_timer_handle_t periodic_timer_handle = (esp_timer_handle_t) arg;
+    /* To start the timer which is running, need to stop it first */
+    ESP_ERROR_CHECK(esp_timer_stop(periodic_timer_handle));
+    ESP_ERROR_CHECK(esp_timer_start_periodic(periodic_timer_handle, 1000000));
+    time_since_boot = esp_timer_get_time();
+    ESP_LOGI(TAG, "Restarted periodic timer with 1s period, time since boot: %lld us",
+            time_since_boot);
+}