一、快速運行

• 示例專案中，選擇WiFi—>scan
• menuconfig配置ESP32C3-Specific—>Rec 0
• 芯片選擇ESP32-C3(Built-in USB JTAG)
• 快速運行ESP-IDF Build, Flash and Monitor（左下角）

二、運行效果

三、程式流程

• nvs_flash_init，初始化默認 NVS 磁區，
• esp_netif_init，初始化底層TCP/IP堆疊
• esp_event_loop_create_default，創建默認事件回圈，
• esp_netif_create_default_wifi_sta，使用默認WiFi Station配置創建esp_netif物件，將netif連接到WiFi并注冊默認WiFi處理程式，
• esp_wifi_init，為 WiFi 驅動初始化 WiFi 分配資源，如 WiFi 控制結構、RX/TX 緩沖區、WiFi NVS 結構等，這個 WiFi 也啟動 WiFi 任務，必須先呼叫此API，然后才能呼叫所有其他WiFi API
• esp_wifi_set_mode，設定WiFi作業模式為station、soft-AP或station+soft-AP，默認模式為soft-AP模式，本程式設定為station
• esp_wifi_start，根據配置，啟動WiFi
• esp_wifi_scan_start，掃描所有有效的AP
• esp_wifi_scan_get_ap_records，獲取上次掃描中找到的AP串列
• esp_wifi_scan_get_ap_num，獲取上次掃描中找到的AP數

四、關鍵函式

4.1 掃描所有有效的AP

• config，掃描的配置
• block，是否堵塞程式運行

/**
  * @brief     Scan all available APs.
  *
  * @attention If this API is called, the found APs are stored in WiFi driver dynamic allocated memory and the
  *            will be freed in esp_wifi_scan_get_ap_records, so generally, call esp_wifi_scan_get_ap_records to cause
  *            the memory to be freed once the scan is done
  * @attention The values of maximum active scan time and passive scan time per channel are limited to 1500 milliseconds.
  *            Values above 1500ms may cause station to disconnect from AP and are not recommended.
  *
  * @param     config  configuration of scanning
  * @param     block if block is true, this API will block the caller until the scan is done, otherwise
  *                         it will return immediately
  *
  * @return
  *    - ESP_OK: succeed
  *    - ESP_ERR_WIFI_NOT_INIT: WiFi is not initialized by esp_wifi_init
  *    - ESP_ERR_WIFI_NOT_STARTED: WiFi was not started by esp_wifi_start
  *    - ESP_ERR_WIFI_TIMEOUT: blocking scan is timeout
  *    - ESP_ERR_WIFI_STATE: wifi still connecting when invoke esp_wifi_scan_start
  *    - others: refer to error code in esp_err.h
  */
esp_err_t esp_wifi_scan_start(const wifi_scan_config_t *config, bool block);

4.2 獲取上次掃描中找到的AP串列

• number，回傳的最大ap個數
• ap_records，回傳的app記錄陣列

/**
  * @brief     Get AP list found in last scan
  *
  * @param[inout]  number As input param, it stores max AP number ap_records can hold.
  *                As output param, it receives the actual AP number this API returns.
  * @param         ap_records  wifi_ap_record_t array to hold the found APs
  *
  * @return
  *    - ESP_OK: succeed
  *    - ESP_ERR_WIFI_NOT_INIT: WiFi is not initialized by esp_wifi_init
  *    - ESP_ERR_WIFI_NOT_STARTED: WiFi is not started by esp_wifi_start
  *    - ESP_ERR_INVALID_ARG: invalid argument
  *    - ESP_ERR_NO_MEM: out of memory
  */
esp_err_t esp_wifi_scan_get_ap_records(uint16_t *number, wifi_ap_record_t *ap_records);

4.3 獲取上次掃描中找到的AP數

• number，存盤上次掃描中找到的API數

/**
  * @brief     Get number of APs found in last scan
  *
  * @param[out] number  store number of APs found in last scan
  *
  * @attention This API can only be called when the scan is completed, otherwise it may get wrong value.
  *
  * @return
  *    - ESP_OK: succeed
  *    - ESP_ERR_WIFI_NOT_INIT: WiFi is not initialized by esp_wifi_init
  *    - ESP_ERR_WIFI_NOT_STARTED: WiFi is not started by esp_wifi_start
  *    - ESP_ERR_INVALID_ARG: invalid argument
  */
esp_err_t esp_wifi_scan_get_ap_num(uint16_t *number);

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