ESP32-C3入门教程 网络篇①——WiFi Scan 快速扫描附近AP无线热点

Posted 2021-10-13 小康师兄

文章目录

• 一、快速运行
• 二、运行效果
• 三、程序流程
• 四、关键函数
• • 4.1 扫描所有有效的AP
  • 4.2 获取上次扫描中找到的AP列表
  • 4.3 获取上次扫描中找到的AP数

一、快速运行

• 示例项目中，选择WiFi—>scan
• menuconfig配置ESP32C3-Specific—>Rec 0
• 芯片选择ESP32-C3(Built-in USB JTAG)
• 快速运行ESP-IDF Build, Flash and Monitor（左下角）

二、运行效果

三、程序流程

• nvs_flash_init，初始化默认 NVS 分区。
• esp_netif_init，初始化底层TCP/IP堆栈
• esp_event_loop_create_default，创建默认事件循环。
• esp_netif_create_default_wifi_sta，使用默认WiFi Station配置创建esp_netif对象，将netif连接到WiFi并注册默认WiFi处理程序。
• esp_wifi_init，为 WiFi 驱动初始化 WiFi 分配资源，如 WiFi 控制结构、RX/TX 缓冲区、WiFi NVS 结构等，这个 WiFi 也启动 WiFi 任务。必须先调用此API，然后才能调用所有其他WiFi API
• esp_wifi_set_mode，设置WiFi工作模式为station、soft-AP或station+soft-AP，默认模式为soft-AP模式。本程序设置为station
• esp_wifi_start，根据配置，启动WiFi
• esp_wifi_scan_start，扫描所有有效的AP
• esp_wifi_scan_get_ap_records，获取上次扫描中找到的AP列表
• esp_wifi_scan_get_ap_num，获取上次扫描中找到的AP数

四、关键函数

4.1 扫描所有有效的AP

• config，扫描的配置
• block，是否堵塞程序运行

/**
  * @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 获取上次扫描中找到的AP列表

• number，返回的最大ap个数
• ap_records，返回的app记录数组

/**
  * @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 获取上次扫描中找到的AP数

• number，存储上次扫描中找到的API数

/**
  * @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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