基于ESP32-C3的RISC-V智能家居中控实战

BH1750（I2C）

BH1750走I2C，封装比DHT11省心。连续高分辨率模式，读出两个字节换算成lux就行。

#include "driver/i2c.h"

#define BH1750_ADDR 0x23

void bh1750_init(i2c_port_t i2c_num) {
    i2c_config_t conf = {
        .mode = I2C_MODE_MASTER,
        .sda_io_num = 5,
        .scl_io_num = 6,
        .sda_pullup_en = GPIO_PULLUP_ENABLE,
        .scl_pullup_en = GPIO_PULLUP_ENABLE,
        .master.clk_speed = 100000
    };
    i2c_param_config(i2c_num, &conf);
    i2c_driver_install(i2c_num, conf.mode, 0, 0, 0);
    
    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, BH1750_ADDR << 1, true);
    i2c_master_write_byte(cmd, 0x10, true);
    i2c_master_stop(cmd);
    i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_PERIOD_MS);
    i2c_cmd_link_delete(cmd);
}

float bh1750_read_lux(i2c_port_t i2c_num) {
    uint8_t data[2];
    i2c_cmd_handle_t cmd = i2c_cmd_link_create();
    i2c_master_start(cmd);
    i2c_master_write_byte(cmd, (BH1750_ADDR << 1) | I2C_MASTER_READ, true);
    i2c_master_read_byte(cmd, &data[0], I2C_MASTER_ACK);
    i2c_master_read_byte(cmd, &data[1], I2C_MASTER_NACK);
    i2c_master_stop(cmd);
    i2c_master_cmd_begin(i2c_num, cmd, 1000 / portTICK_PERIOD_MS);
    i2c_cmd_link_delete(cmd);
    
    uint16_t raw = (data[0] << 8) | data[1];
    return raw / 1.2;
}

FreeRTOS分任务跑

裸机轮询没法同时搞定传感器读取、继电器控制和网络通信，必须上RTOS。这里简单创建两个任务：一个每5秒读传感器，另一个根据光照自动开关灯。

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "dht11.h"
#include "bh1750.h"
#include "nvs_flash.h"

void sensor_task(void* pvParameters) {
    uint8_t hum, temp;
    float lux;
    while (1) {
        if (dht11_read(&hum, &temp)) {
            printf("Temp: %d°C, Hum: %d%%\n", temp, hum);
        }
        lux = bh1750_read_lux(I2C_NUM_0);
        printf("Light: %.2f lux\n", lux);
        vTaskDelay(pdMS_TO_TICKS(5000));
    }
}

void relay_control_task(void* pvParameters) {
    gpio_set_direction(10, GPIO_MODE_OUTPUT);
    while (1) {
        float lux = bh1750_read_lux(I2C_NUM_0);
        gpio_set_level(10, (lux < 50) ? 1 : 0);
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

void app_main(void) {
    nvs_flash_init();
    dht11_init();
    bh1750_init(I2C_NUM_0);
    xTaskCreate(sensor_task, "sensor", 2048, NULL, 5, NULL);
    xTaskCreate(relay_control_task, "relay", 2048, NULL, 4, NULL);
}

烧录idf.py build flash monitor就能看到串口输出。

Wi-Fi与MQTT：数据上云

智能家居不联网就差点意思。ESP32-C3连Wi-Fi后用MQTT上报传感器数据，这里用的免费公共broker broker.emqx.io，测试可以，正式环境还是自己搭一个。

#include "esp_wifi.h"
#include "esp_event.h"
#include "nvs_flash.h"

void wifi_init_sta(void) {
    nvs_flash_init();
    esp_netif_init();
    esp_event_loop_create_default();
    esp_netif_create_default_wifi_sta();
    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    esp_wifi_init(&cfg);
    wifi_config_t wifi_config = {
        .sta = {
            .ssid = "Your_SSID",
            .password = "Your_PASSWORD",
        },
    };
    esp_wifi_set_mode(WIFI_MODE_STA);
    esp_wifi_set_config(WIFI_IF_STA, &wifi_config);
    esp_wifi_start();
    esp_wifi_connect();
}

#include "mqtt_client.h"

static esp_mqtt_client_handle_t client;

void mqtt_app_start(void) {
    esp_mqtt_client_config_t mqtt_cfg = {
        .broker.address.uri = "mqtt://broker.emqx.io",
        .credentials.client_id = "riscv_home_controller_001"
    };
    client = esp_mqtt_client_init(&mqtt_cfg);
    esp_mqtt_client_start(client);
}

void publish_sensor_data(float temp, float hum, float lux) {
    char payload[100];
    snprintf(payload, sizeof(payload), "{\"temp\":%.1f,\"hum\":%.1f,\"lux\":%.1f}", temp, hum, lux);
    esp_mqtt_client_publish(client, "home/sensors", payload, 0, 1, 0);
}

用MQTT Explorer订阅home/sensors就能看到实时数据。

BLE本地控制

万一Wi-Fi挂了，BLE可以当备用通道。ESP32-C3的BLE 5.0建一个GATT服务，一个特征读传感器数据，另一个特征写继电器状态。

#include "esp_bt.h"
#include "esp_gap_ble_api.h"
#include "esp_gatts_api.h"

#define SERVICE_UUID 0xFFE0
#define CHAR_SENSOR_UUID 0xFFE1
#define CHAR_RELAY_UUID 0xFFE2

static uint16_t sensor_handle, relay_handle;

void gatts_event_handler(esp_gatts_cb_event_t event, esp_gatt_if_t gatts_if, esp_ble_gatts_cb_param_t* param) {
    switch (event) {
        case ESP_GATTS_REG_EVT:
            esp_ble_gap_set_device_name("RISC-V Home Hub");
            esp_ble_gatts_create_service(gatts_if, &service_uuid, 20);
            break;
        case ESP_GATTS_CREATE_EVT:
            esp_ble_gatts_start_service(param->create.service_handle);
            esp_ble_gatts_add_char(param->create.service_handle, &char_sensor_uuid, ESP_GATT_PERM_READ, ESP_GATT_CHAR_PROP_BIT_READ, NULL, NULL);
            esp_ble_gatts_add_char(param->create.service_handle, &char_relay_uuid, ESP_GATT_PERM_READ | ESP_GATT_PERM_WRITE, ESP_GATT_CHAR_PROP_BIT_READ | ESP_GATT_CHAR_PROP_BIT_WRITE, NULL, NULL);
            break;
        case ESP_GATTS_READ_EVT:
            if (param->read.handle == sensor_handle) {
                char data[50];
                snprintf(data, sizeof(data), "%.1f,%.1f,%.1f", temp, hum, lux);
                esp_ble_gatts_send_response(gatts_if, param->read.conn_id, param->read.trans_id, ESP_GATT_OK, strlen(data), (uint8_t*)data);
            }
            break;
        case ESP_GATTS_WRITE_EVT:
            if (param->write.handle == relay_handle) {
                gpio_set_level(10, param->write.value[0] ? 1 : 0);
            }
            break;
    }
}

手机装个nRF Connect就能扫描设备、读写特征。

简易Web界面

再跑一个HTTP server，同一个Wi-Fi下的设备就能用浏览器控制，纯裸页，能用就行。

#include "esp_http_server.h"

static httpd_handle_t server = NULL;

esp_err_t sensor_get_handler(httpd_req_t* req) {
    char resp[200];
    snprintf(resp, sizeof(resp), "<html><body>"
        "<h1>RISC-V Smart Hub</h1>"
        "<p>Temperature: %d°C</p>"
        "<p>Humidity: %d%%</p>"
        "<p>Light: %.1f lux</p>"
        "<a href='/relay?on=1'>Turn ON Light</a> | "
        "<a href='/relay?on=0'>Turn OFF Light</a>"
        "</body></html>", temp, hum, lux);
    httpd_resp_send(req, resp, HTTPD_RESP_USE_STRLEN);
    return ESP_OK;
}

esp_err_t relay_handler(httpd_req_t* req) {
    char* buf = httpd_req_get_url_query_str(req);
    if (buf) {
        char val[10];
        if (httpd_query_key_value(buf, "on", val, sizeof(val)) == ESP_OK) {
            gpio_set_level(10, atoi(val));
        }
        free(buf);
    }
    httpd_resp_sendstr(req, "OK");
    return ESP_OK;
}

void start_webserver(void) {
    httpd_config_t config = HTTPD_DEFAULT_CONFIG();
    if (httpd_start(&server, &config) == ESP_OK) {
        httpd_register_uri_handler(server, &(httpd_uri_t){
            .uri = "/",
            .method = HTTP_GET,
            .handler = sensor_get_handler
        });
        httpd_register_uri_handler(server, &(httpd_uri_t){
            .uri = "/relay",
            .method = HTTP_GET,
            .handler = relay_handler
        });
    }
}

加点安全

MQTT明文传很不安全，换成TLS端口mqtts://broker.emqx.io:8883，再把CA证书嵌进固件。

esp_mqtt_client_config_t mqtt_cfg = {
    .broker.address.uri = "mqtts://broker.emqx.io:8883",
    .broker.verification.certificate = (const char*)server_cert_pem_start,
};

OTA更新也要走HTTPS，校验服务器证书，防止固件被篡改。

esp_https_ota_config_t ota_config = {
    .url = "https://your-server.com/firmware.bin",
    .cert_pem = server_cert_pem_start,
};
esp_https_ota(&ota_config);

更详细的配置看ESP32 Secure OTA文档。

低功耗的一点考虑

要是用电池供电，必须开深度睡眠。定时唤醒后干活，干完再睡。代价是RAM全丢，重要状态得提前存RTC memory或Flash。

#include "esp_sleep.h"
esp_sleep_enable_timer_wakeup(10 * 60 * 1000000);
esp_deep_sleep_start();

收尾

这样一套下来，从硬件到固件、从本地到云端，RISC-V智能家居中控就跑通了。成本比ARM方案低不少，而且ESP-IDF生态很方便。后续可以加语音识别、Zigbee网关，或者接入HomeAssistant。代码全部开源，有兴趣的可以拿去改。