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03 Nov 2017 | 单片机
高度集成:ESP32 集成了天线开关、射频 balun、功率放大器、低噪放大器、过滤器和电源管理模块,整个解决方案占用了最少的印刷电路板面积。
WiFi+双模蓝:ESP32 可作为独立系统运行应用程序或是主机 MCU 的从设备,通过 SPI / SDIO 或 I2C / UART 接口提供 Wi-Fi 和蓝牙(传统蓝牙和低功耗蓝牙)功能。
esp32有多种编程方式,这里我使用以arduino为内核的PlatformIO IDE。
以下是esp32连接wifi通过get方法获取example.com 测试网站上的数据。
/* HTTP GET Example using plain POSIX sockets 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 <string.h> #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "freertos/event_groups.h" #include "esp_system.h" #include "esp_wifi.h" #include "esp_event_loop.h" #include "esp_log.h" #include "nvs_flash.h" #include "lwip/err.h" #include "lwip/sockets.h" #include "lwip/sys.h" #include "lwip/netdb.h" #include "lwip/dns.h" /* The examples use simple WiFi configuration that you can set via 'make menuconfig'. If you'd rather not, just change the below entries to strings with the config you want - ie #define EXAMPLE_WIFI_SSID "mywifissid" */ #define EXAMPLE_WIFI_SSID your_wifi_ssid #define EXAMPLE_WIFI_PASS your_wifi_pass /* FreeRTOS event group to signal when we are connected & ready to make a request */ static EventGroupHandle_t wifi_event_group; /* The event group allows multiple bits for each event, but we only care about one event - are we connected to the AP with an IP? */ const int CONNECTED_BIT = BIT0; /* Constants that aren't configurable in menuconfig */ #define WEB_SERVER "example.com" #define WEB_PORT 80 #define WEB_URL "http://example.com/" static const char *TAG = "example"; static const char *REQUEST = "GET " WEB_URL " HTTP/1.1\n" "Host: "WEB_SERVER"\n" "User-Agent: esp-idf/1.0 esp32\n" "\n"; static esp_err_t event_handler(void *ctx, system_event_t *event) { switch(event->event_id) { case SYSTEM_EVENT_STA_START: esp_wifi_connect(); break; case SYSTEM_EVENT_STA_GOT_IP: xEventGroupSetBits(wifi_event_group, CONNECTED_BIT); break; case SYSTEM_EVENT_STA_DISCONNECTED: /* This is a workaround as ESP32 WiFi libs don't currently auto-reassociate. */ esp_wifi_connect(); xEventGroupClearBits(wifi_event_group, CONNECTED_BIT); break; default: break; } return ESP_OK; } static void initialise_wifi(void) { tcpip_adapter_init(); wifi_event_group = xEventGroupCreate(); ESP_ERROR_CHECK( esp_event_loop_init(event_handler, NULL) ); wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT(); ESP_ERROR_CHECK( esp_wifi_init(&cfg) ); ESP_ERROR_CHECK( esp_wifi_set_storage(WIFI_STORAGE_RAM) ); wifi_config_t wifi_config = { .sta = { .ssid = EXAMPLE_WIFI_SSID, .password = EXAMPLE_WIFI_PASS, }, }; ESP_LOGI(TAG, "Setting WiFi configuration SSID %s...", wifi_config.sta.ssid); ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) ); ESP_ERROR_CHECK( esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config) ); ESP_ERROR_CHECK( esp_wifi_start() ); } static void http_get_task(void *pvParameters) { const struct addrinfo hints = { .ai_family = AF_INET, .ai_socktype = SOCK_STREAM, }; struct addrinfo *res; struct in_addr *addr; int s, r; char recv_buf[64]; while(1) { /* Wait for the callback to set the CONNECTED_BIT in the event group. */ xEventGroupWaitBits(wifi_event_group, CONNECTED_BIT, false, true, portMAX_DELAY); ESP_LOGI(TAG, "Connected to AP"); int err = getaddrinfo(WEB_SERVER, "80", &hints, &res); if(err != 0 || res == NULL) { ESP_LOGE(TAG, "DNS lookup failed err=%d res=%p", err, res); vTaskDelay(1000 / portTICK_PERIOD_MS); continue; } /* Code to print the resolved IP. Note: inet_ntoa is non-reentrant, look at ipaddr_ntoa_r for "real" code */ addr = &((struct sockaddr_in *)res->ai_addr)->sin_addr; ESP_LOGI(TAG, "DNS lookup succeeded. IP=%s", inet_ntoa(*addr)); s = socket(res->ai_family, res->ai_socktype, 0); if(s < 0) { ESP_LOGE(TAG, "... Failed to allocate socket."); freeaddrinfo(res); vTaskDelay(1000 / portTICK_PERIOD_MS); continue; } ESP_LOGI(TAG, "... allocated socket\r\n"); if(connect(s, res->ai_addr, res->ai_addrlen) != 0) { ESP_LOGE(TAG, "... socket connect failed errno=%d", errno); close(s); freeaddrinfo(res); vTaskDelay(4000 / portTICK_PERIOD_MS); continue; } ESP_LOGI(TAG, "... connected"); freeaddrinfo(res); if (write(s, REQUEST, strlen(REQUEST)) < 0) { ESP_LOGE(TAG, "... socket send failed"); close(s); vTaskDelay(4000 / portTICK_PERIOD_MS); continue; } ESP_LOGI(TAG, "... socket send success"); /* Read HTTP response */ do { bzero(recv_buf, sizeof(recv_buf)); r = read(s, recv_buf, sizeof(recv_buf)-1); for(int i = 0; i < r; i++) { putchar(recv_buf[i]); } } while(r > 0); ESP_LOGI(TAG, "... done reading from socket. Last read return=%d errno=%d\r\n", r, errno); close(s); for(int countdown = 10; countdown >= 0; countdown--) { ESP_LOGI(TAG, "%d... ", countdown); vTaskDelay(1000 / portTICK_PERIOD_MS); } ESP_LOGI(TAG, "Starting again!"); } } void app_main() { nvs_flash_init(); initialise_wifi(); xTaskCreate(&http_get_task, "http_get_task", 2048, NULL, 5, NULL); }
其中,ssid为wifi的名称。
效果如下: