WiFi-scan例程分析

本例程比较简单，每行代码的作用都注释在旁边了。至于这些API的参数、返回值等请自行查阅官方文档，非常详细。（建议下载为pdf，查阅速度更快）

本例程的功能是扫描附近可用的AP，并将它们的信息打印出来。

/* Scan 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.
*/

/*
    This example shows how to scan for available set of APs.
*/
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"
#include "esp_wifi.h"
#include "esp_log.h"
#include "esp_event.h"
#include "nvs_flash.h"

//扫描列表的大小
#define DEFAULT_SCAN_LIST_SIZE CONFIG_EXAMPLE_SCAN_LIST_SIZE

static const char *TAG = "scan";

static void print_auth_mode(int authmode)
{
    switch (authmode) {
    case WIFI_AUTH_OPEN:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_OPEN");
        break;
    case WIFI_AUTH_WEP:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WEP");
        break;
    case WIFI_AUTH_WPA_PSK:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA_PSK");
        break;
    case WIFI_AUTH_WPA2_PSK:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA2_PSK");
        break;
    case WIFI_AUTH_WPA_WPA2_PSK:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA_WPA2_PSK");
        break;
    case WIFI_AUTH_WPA2_ENTERPRISE:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA2_ENTERPRISE");
        break;
    case WIFI_AUTH_WPA3_PSK:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA3_PSK");
        break;
    case WIFI_AUTH_WPA2_WPA3_PSK:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_WPA2_WPA3_PSK");
        break;
    default:
        ESP_LOGI(TAG, "Authmode \tWIFI_AUTH_UNKNOWN");
        break;
    }
}

static void print_cipher_type(int pairwise_cipher, int group_cipher)
{
    switch (pairwise_cipher) {
    case WIFI_CIPHER_TYPE_NONE:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_NONE");
        break;
    case WIFI_CIPHER_TYPE_WEP40:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_WEP40");
        break;
    case WIFI_CIPHER_TYPE_WEP104:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_WEP104");
        break;
    case WIFI_CIPHER_TYPE_TKIP:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_TKIP");
        break;
    case WIFI_CIPHER_TYPE_CCMP:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_CCMP");
        break;
    case WIFI_CIPHER_TYPE_TKIP_CCMP:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_TKIP_CCMP");
        break;
    default:
        ESP_LOGI(TAG, "Pairwise Cipher \tWIFI_CIPHER_TYPE_UNKNOWN");
        break;
    }

    switch (group_cipher) {
    case WIFI_CIPHER_TYPE_NONE:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_NONE");
        break;
    case WIFI_CIPHER_TYPE_WEP40:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_WEP40");
        break;
    case WIFI_CIPHER_TYPE_WEP104:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_WEP104");
        break;
    case WIFI_CIPHER_TYPE_TKIP:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_TKIP");
        break;
    case WIFI_CIPHER_TYPE_CCMP:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_CCMP");
        break;
    case WIFI_CIPHER_TYPE_TKIP_CCMP:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_TKIP_CCMP");
        break;
    default:
        ESP_LOGI(TAG, "Group Cipher \tWIFI_CIPHER_TYPE_UNKNOWN");
        break;
    }
}

/* Initialize Wi-Fi as sta and set scan method */
static void wifi_scan(void)
{
    ESP_ERROR_CHECK(esp_netif_init());//初始化TCP/IP协议栈
    ESP_ERROR_CHECK(esp_event_loop_create_default());//创建默认事件循环
    esp_netif_t *sta_netif = esp_netif_create_default_wifi_sta();//使用默认的WiFi Station配置创建ESP_NETIF对象，将NETIF添加到WiFi，并注册默认WiFi处理程序。
    assert(sta_netif);//如果sta_netif为空，即创建失败，则向stderr打印一条错误信息，并调用abort终止程序运行

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();//创建wifi的默认初始化配置信息（结构体）
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));//初始化wifi

    uint16_t number = DEFAULT_SCAN_LIST_SIZE;
    wifi_ap_record_t ap_info[DEFAULT_SCAN_LIST_SIZE];//创建一个指定大小的包含AP信息的结构体列表
    uint16_t ap_count = 0;
    memset(ap_info, 0, sizeof(ap_info));//为这个列表分配内存

    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));//设置wifi的工作模式为STA
    ESP_ERROR_CHECK(esp_wifi_start());//启动wifi
    esp_wifi_scan_start(NULL, true);//启动扫描，并设置为阻塞当前程序直至扫描完成
    ESP_ERROR_CHECK(esp_wifi_scan_get_ap_records(&number, ap_info));//获取指定个数的AP，并存入ap_info中
    ESP_ERROR_CHECK(esp_wifi_scan_get_ap_num(&ap_count));//获取实际扫描到的AP个数

    //将实际扫描到的AP数以及每个AP的信息打印出来
    ESP_LOGI(TAG, "Total APs scanned = %u", ap_count);
    for (int i = 0; (i < DEFAULT_SCAN_LIST_SIZE) && (i < ap_count); i++) {
        ESP_LOGI(TAG, "SSID \t\t%s", ap_info[i].ssid);
        ESP_LOGI(TAG, "RSSI \t\t%d", ap_info[i].rssi);
        print_auth_mode(ap_info[i].authmode);
        if (ap_info[i].authmode != WIFI_AUTH_WEP) {
            print_cipher_type(ap_info[i].pairwise_cipher, ap_info[i].group_cipher);
        }
        ESP_LOGI(TAG, "Channel \t\t%d\n", ap_info[i].primary);
    }

}

void app_main(void)
{
    //初始化NVS（非易失性存储），也就是flash
    esp_err_t ret = nvs_flash_init();
    //如果初始化失败，则删除默认NVS分区后重新初始化一次
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_ERROR_CHECK(nvs_flash_erase());
        ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK( ret );
    //启动wifi扫描
    wifi_scan();
}

WiFi-scan例程分析