基于 ESP8266_RTOS_SDK 驱动 DHT11

概述

DHT11模块使用一根data线实现信号触发以及数据反馈，信号格式参考如下

https://zhuanlan.zhihu.com/p/347904660

本文使用GPIO中断的方式采集反馈数据

知识点：GPIO、中断、事件组、定时器

平台

芯片 ESP8266EX

模组 ESP-12F

开发板 NodeMCU

SDK ESP8266_RTOS_SDK

branch master

code

点击查看代码

typedef struct dht11_isr_arg_t{
    uint8_t status;//0-未发送触发信号，1-已发送触发信号
    uint8_t num;//已采集的波形数量，有效数据是40bit
    uint8_t bit_status;//采集1个波形的状态，0-接收到上升沿开始，1-接收到下降沿结束采集
    EventGroupHandle_t event;//事件组
    uint32_t clk;//用于记录波形时间
    uint64_t data;//最终采集到的数据
}dht11_isr_arg_t;

/**
 * @brief 定时器中断函数,5个clk=1us
 */
void timer_isr(void *arg){
    gpio_set_level(GPIO_NUM_2, !gpio_get_level(GPIO_NUM_2));

    dht11_isr_arg_t *isr_arg = (dht11_isr_arg_t *)arg;
    BaseType_t base;
    xEventGroupSetBitsFromISR(isr_arg->event, 0x01, &base);
}

/**
 * @brief 初始化定时器
 */
void timer_init(void *arg){
    hw_timer_init(timer_isr, arg);//注册定时器中断函数
    hw_timer_set_reload(true);//允许重载，即循环定时，不止一次
    hw_timer_set_clkdiv(TIMER_CLKDIV_16);//16分频
    hw_timer_set_intr_type(TIMER_EDGE_INT);
    hw_timer_set_load_data((TIMER_BASE_CLK >> hw_timer_get_clkdiv()));//5000000
    hw_timer_enable(true);
}

/**
 * @brief 初始化LED
 */
void led_init(){
    gpio_config_t io_conf;
    io_conf.intr_type = GPIO_INTR_DISABLE;
    io_conf.mode = GPIO_MODE_OUTPUT;
    io_conf.pin_bit_mask = 1 << GPIO_NUM_2;
    io_conf.pull_down_en = 0;
    io_conf.pull_up_en = 0;
    gpio_config(&io_conf);
}

/**
 * @brief GPIO5的中断函数，上升沿和下降沿均触发
 */
void dht11_isr(void *arg){
    dht11_isr_arg_t *isr_arg = (dht11_isr_arg_t *)arg;
    //未发送触发信号直接退出
    if(0 == isr_arg->status) return;

    //上升沿开始计时，下降沿结束计时并将数据写入
    switch(isr_arg->bit_status){
        case 0:
            if(1 == gpio_get_level(GPIO_NUM_5)){
                isr_arg->clk = hw_timer_get_count_data();
                isr_arg->bit_status = 1;
            }
            break;
        case 1:
            if(0 == gpio_get_level(GPIO_NUM_5)){
                isr_arg->data = isr_arg->data << 1;
                //防止两次计时中间经历了定时器重载，实际上在定时器1s中断的情况下基本不存在，因为获取全部41bit数据大概只需要4.1ms
                if(isr_arg->clk < hw_timer_get_count_data()){
                    isr_arg->clk += (TIMER_BASE_CLK >> hw_timer_get_clkdiv());
                }
                //高电平超过40us即认定为数据1
                if(40*5 <= (isr_arg->clk - hw_timer_get_count_data())){
                    isr_arg->data |= 0x01;
                }
                isr_arg->num++;
                isr_arg->bit_status = 0;
                //40bit数据加上触发信号的响应，共41bit信号
                if(41 <= isr_arg->num){
                    BaseType_t base;
                    xEventGroupSetBitsFromISR(isr_arg->event, 0x02, &base);
                }
            }
            break;
        default:
            break;
    }
}

/**
 * @brief 使用中断的形式驱动DHT11
 * @brief 技术点-GPIO、中断、定时器、事件组
 */
void task_dht11(void *arg){
    dht11_isr_arg_t isr_arg;
    isr_arg.event = xEventGroupCreate();
    //因data线同时需要输入输出，配置为开漏并使用内部上拉
    gpio_config_t conf;
    conf.mode = GPIO_MODE_OUTPUT_OD;
    conf.intr_type = GPIO_INTR_ANYEDGE;
    conf.pin_bit_mask = 1 << GPIO_NUM_5;
    conf.pull_down_en = 0;
    conf.pull_up_en = 1;
    gpio_config(&conf);
    gpio_install_isr_service(0);
    gpio_isr_handler_add(GPIO_NUM_5, dht11_isr, &isr_arg);

    led_init();
    timer_init(&isr_arg);

    while(1){
        //等待定时器事件产生，发送触发信号
        EventBits_t bits = xEventGroupWaitBits(isr_arg.event, 0x03, pdTRUE, pdFALSE, portMAX_DELAY);
        if(0x01 != (bits | 0x01)) continue;
        isr_arg.data = 0;
        isr_arg.status = 0;
        isr_arg.bit_status = 0;
        isr_arg.clk = 0;
        isr_arg.num = 0;
        gpio_set_level(GPIO_NUM_5, 0);
        os_delay_us(20000);
        gpio_set_level(GPIO_NUM_5, 1);
        isr_arg.status = 1;
        os_delay_us(30);
        printf("wait dht11 init data\n");

        //等待数据采集完毕
        bits = xEventGroupWaitBits(isr_arg.event, 0x03, pdTRUE, pdFALSE, portMAX_DELAY);
        //防止DHT11异常，当再次接收到定时器事件时重置，间隔1s足够DH11正常响应
        if(0x02 != (bits | 0x02)) continue;
        uint8_t *data = &(isr_arg.data);
        for(int i = 0; i < 8; i++){
            printf("data[%d] = %d ", i, data[i]);
        }
        if(data[0] == (data[1] + data[2] + data[3] + data[4])){
            printf("\nhumidity = %d.%d temperature = %d.%d\n", data[4], data[3], data[2], data[1]);
        }
    }
}

效果如下

点击查看代码

[21:32:11:516] wait dht11 init data␍␊
[21:32:11:526] data[0] = 78 data[1] = 4 data[2] = 27 data[3] = 1 data[4] = 46 data[5] = 1 data[6] = 0 data[7] = 0 ␍␊
[21:32:11:539] humidity = 46.1 temperature = 27.4␍␊
[21:32:12:517] wait dht11 init data␍␊
[21:32:12:527] data[0] = 78 data[1] = 5 data[2] = 27 data[3] = 0 data[4] = 46 data[5] = 1 data[6] = 0 data[7] = 0 ␍␊
[21:32:12:540] humidity = 46.0 temperature = 27.5␍␊
[21:32:13:517] wait dht11 init data␍␊
[21:32:13:527] data[0] = 92 data[1] = 7 data[2] = 27 data[3] = 9 data[4] = 49 data[5] = 1 data[6] = 0 data[7] = 0 ␍␊
[21:32:13:540] humidity = 49.9 temperature = 27.7␍␊