ESP-IDF Patterns

1// ── Normal C (desktop) ──
2// Program runs once and exits
3int main(int argc, char *argv[]) {
4    printf("Hello!\n");
5    process_data();
6    return 0;  // OS cleans up everything
7}
8
9// ── Embedded C (ESP-IDF) ──
10// Program runs forever — there is no OS to return to
11void app_main(void) {
12    init_hardware();
13
14    while (1) {  // super loop — or use FreeRTOS tasks
15        read_sensors();
16        process_data();
17        actuate_outputs();
18        vTaskDelay(pdMS_TO_TICKS(100));  // yield CPU — don't busy-wait!
19    }
20    // never reaches here
21}

1// ── Normal C (desktop) ──
2// Print error and exit — OS handles cleanup
3FILE *f = fopen("data.txt", "r");
4if (f == NULL) {
5    perror("Failed to open file");
6    exit(1);  // just quit
7}
8
9// ── Embedded C (ESP-IDF) ──
10// Must handle error and continue — there is no OS to exit to
11esp_err_t ret = i2c_master_init();
12if (ret != ESP_OK) {
13    ESP_LOGE("MAIN", "I2C init failed: %s", esp_err_to_name(ret));
14    // Options: retry, use fallback, or restart the device
15    esp_restart();  // last resort — reboot the chip
16}

1// Object-like macro — constant replacement
2#define LED_GPIO 2
3
4// Conditional compilation (controlled by menuconfig)
5#define CONFIG_ENABLE_WIFI 1
6
7#if CONFIG_ENABLE_WIFI
8    void wifi_init(void) { /* ... */ }
9#endif
10
11// ESP-IDF logging macros (you'll use these constantly)
12#include "esp_log.h"
13#define TAG "MAIN"
14
15ESP_LOGI(TAG, "Temperature: %.1f", 24.5);   // Info (Green)
16ESP_LOGW(TAG, "Low battery: %d%%", 15);     // Warning (Yellow)
17ESP_LOGE(TAG, "Sensor read failed!");       // Error (Red)

1esp_err_t ret = nvs_flash_init();
2
3if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
4    ESP_ERROR_CHECK(nvs_flash_erase());
5    ret = nvs_flash_init();
6}
7
8// ESP_ERROR_CHECK will immediately crash and reboot the board if ret != ESP_OK
9ESP_ERROR_CHECK(ret);

1// 1. Create and fill the configuration struct
2gpio_config_t io_conf = {
3    .pin_bit_mask = (1ULL << 2),
4    .mode = GPIO_MODE_OUTPUT,
5    .pull_up_en = GPIO_PULLUP_DISABLE,
6    .pull_down_en = GPIO_PULLDOWN_DISABLE,
7    .intr_type = GPIO_INTR_DISABLE,
8};
9
10// 2. Pass a pointer to the struct to apply the configuration
11gpio_config(&io_conf);

1TaskHandle_t my_task;
2
3xTaskCreate(
4    my_task_function,
5    "Task Name",
6    4096,
7    NULL,
8    1,
9    &my_task // Pass the address so FreeRTOS can give you the handle
10);
11
12// Later, you can use that handle to suspend or delete the task
13vTaskDelete(my_task);