RISC-V 智能家居中控系统实战：硬件、固件与通信全链路解析

验证安装：idf.py --version。

第三步：裸机驱动开发

在深入 RTOS 前，先理解底层时序控制。

示例 1：DHT11 温湿度读取（Bit-banging）

DHT11 使用单总线协议，对时序要求严格。以下是简化版驱动逻辑：

// dht11.c
#include "driver/gpio.h"
#include "esp_timer.h"

#define DHT11_PIN 8

void dht11_init() {
    gpio_set_direction(DHT11_PIN, GPIO_MODE_OUTPUT);
    gpio_set_level(DHT11_PIN, 1);
}

bool dht11_read(uint8_t* humidity, uint8_t* temperature) {
    uint8_t data[5] = {0};
    
    // 主机拉低至少 18ms
    gpio_set_direction(DHT11_PIN, GPIO_MODE_OUTPUT);
    gpio_set_level(DHT11_PIN, 0);
    esp_rom_delay_us(18000);
    
    // 拉高并切换为输入，等待响应
    gpio_set_level(DHT11_PIN, 1);
    esp_rom_delay_us(30);
    gpio_set_direction(DHT11_PIN, GPIO_MODE_INPUT);
    
    while(gpio_get_level(DHT11_PIN) == 0); // 等待变高
    while(gpio_get_level(DHT11_PIN) == 1); // 等待变低
    
    // 读取 40 位数据
    for(int i = 0; i < 40; i++) {
        while(gpio_get_level(DHT11_PIN) == 0);
        uint32_t t = esp_timer_get_time();
        while(gpio_get_level(DHT11_PIN) == 1);
        uint32_t dt = esp_timer_get_time() - t;
        
        data[i/8] <<= 1;
        if(dt > 40) data[i/8] |= 1; // 高电平>40us 为 1
    }
    
    // 校验和
    if(data[4] == (data[0] + data[1] + data[2] + data[3])) {
        *humidity = data[0];
        *temperature = data[2];
        return true;
    }
    return false;
}

实际项目中建议使用官方组件以获得更高稳定性。

示例 2：BH1750 光照传感器（I2C）

// bh1750.c
#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);
    
    // 发送启动命令 0x10 (连续高分辨率模式)
    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; // 转换为 lux
}

第四步：引入 FreeRTOS 实现多任务调度

裸机难以管理多个传感器和通信任务。使用 FreeRTOS 创建独立任务：

// main.c
#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)); // 每 5 秒读一次
    }
}

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); // 暗则开灯
        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);
}

烧录后通过串口监视器查看数据。

第五步：Wi-Fi 连接与 MQTT 通信

连接 Wi-Fi

#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();
}

MQTT 客户端

#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);
}

公共测试服务器地址：broker.emqx.io，端口 1883。

第六步：BLE 本地控制

当 Wi-Fi 不可用时，BLE 可作为备用通道。ESP32-C3 支持 BLE 5.0。

// ble_service.c
#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");
            break;
        case ESP_GATTS_CREATE_EVT:
            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_WRITE_EVT:
            if(param->write.handle == relay_handle) {
                gpio_set_level(10, param->write.value[0] ? 1 : 0);
            }
            break;
    }
}

配合手机 App 即可扫描并控制设备。

第七步：本地 Web 界面

无需安装 App，直接在浏览器访问设备 IP 进行控制。

#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 });
    }
}

第八步：安全加固

默认通信是明文的，需启用 TLS。

MQTT over TLS

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

将 CA 证书嵌入固件，可通过 CMake 导入。

OTA 安全更新

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);

第九步：低功耗优化

对于电池供电场景，需启用深度睡眠：

#include "esp_sleep.h"

// 每 10 分钟唤醒一次
esp_sleep_enable_timer_wakeup(10*60*1000000);
esp_deep_sleep_start();

注意：深度睡眠会丢失 RAM 数据，关键状态需存入 RTC 内存或 Flash。

总结

本文完成了从硬件搭建到固件开发、从本地控制到云端通信的完整 RISC-V 智能家居中控系统。整个项目体现了 RISC-V 在 IoT 领域的潜力：低成本、高自由度、强生态兼容性。未来可扩展语音识别、Zigbee 网关或人脸识别门禁等功能。