ESP32_RMT驱动DHT11

DHT.c文件

#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <driver/rmt_rx.h>
#include <driver/rmt_tx.h>
#include <soc/rmt_reg.h>
#include "esp_log.h"
#include "driver/gpio.h"
#include "esp_system.h"
#include "esp32/rom/ets_sys.h"

#define TAG        "DHT11"

int DHT11_IO =25;
//rmt接收通道句柄
static rmt_channel_handle_t rx_chan_handle = NULL;

//数据接收队列
static QueueHandle_t rx_receive_queue = NULL;

// 将RMT读取到的脉冲数据处理为温度和湿度
static int parse_items(rmt_symbol_word_t *item, int item_num, int *humidity, int *temp_x10);

//接收完成回调函数
static bool IRAM_ATTR example_rmt_rx_done_callback(rmt_channel_handle_t channel, const rmt_rx_done_event_data_t *edata, void *user_data)
{
    BaseType_t high_task_wakeup = pdFALSE;
    QueueHandle_t rx_receive_queue = (QueueHandle_t)user_data;
    // send the received RMT symbols to the parser task
    xQueueSendFromISR(rx_receive_queue, edata, &high_task_wakeup);
    return high_task_wakeup == pdTRUE;
}

/** DHT11初始化
 * @param DHT11_IO GPIO引脚
 * @return 无
*/
void DHT11_Init()
{
    
    rmt_rx_channel_config_t rx_chan_config = {
        .clk_src = RMT_CLK_SRC_APB,   // 选择时钟源
        .resolution_hz = 1000 * 1000,       // 1 MHz 滴答分辨率，即 1 滴答 = 1 µs
        .mem_block_symbols = 64,          // 内存块大小，即 64 * 4 = 256 字节
        .gpio_num = DHT11_IO,           // GPIO 编号
        .flags.invert_in = false,         // 不反转输入信号
        .flags.with_dma = false,          // 不需要 DMA 后端(ESP32S3才有)
    };
    //创建rmt接收通道
    ESP_ERROR_CHECK(rmt_new_rx_channel(&rx_chan_config, &rx_chan_handle));
 
    //新建接收数据队列
    rx_receive_queue = xQueueCreate(20, sizeof(rmt_rx_done_event_data_t));
    assert(rx_receive_queue);

    //注册接收完成回调函数
     ESP_LOGI(TAG, "register RX done callback");
    rmt_rx_event_callbacks_t cbs = {
        .on_recv_done = example_rmt_rx_done_callback,
    };
    ESP_ERROR_CHECK(rmt_rx_register_event_callbacks(rx_chan_handle, &cbs, rx_receive_queue));

    //使能RMT接收通道
    ESP_ERROR_CHECK(rmt_enable(rx_chan_handle));
}

// 将RMT读取到的脉冲数据处理为温度和湿度(rmt_symbol_word_t称为RMT符号)
static int parse_items(rmt_symbol_word_t *item, int item_num, int *humidity, int *temp_x10)
{
    int i = 0;
    unsigned int rh = 0, temp = 0, checksum = 0;
    if (item_num < 41){                    // 检查是否有足够的脉冲数
        //ESP_LOGI(TAG, "item_num < 41  %d",item_num);
        return 0;
    }
    if(item_num > 41)
        item++;                                // 跳过开始信号脉冲

    for (i = 0; i < 16; i++, item++)    // 提取湿度数据
    {
        uint16_t duration = 0;
        if(item->level0)
            duration = item->duration0;
        else
            duration = item->duration1;
        rh = (rh << 1) + (duration < 35 ? 0 : 1);
    }


    for (i = 0; i < 16; i++, item++)    // 提取温度数据
    {
        uint16_t duration = 0;
        if(item->level0)
            duration = item->duration0;
        else
            duration = item->duration1;
        temp = (temp << 1) + (duration < 35 ? 0 : 1);
    }
    
    for (i = 0; i < 8; i++, item++){    // 提取校验数据
    
        uint16_t duration = 0;
        if(item->level0)
            duration = item->duration0;
        else
            duration = item->duration1;
        checksum = (checksum << 1) + (duration < 35 ? 0 : 1);
    }
    // 检查校验
    if ((((temp >> 8) + temp + (rh >> 8) + rh) & 0xFF) != checksum){
        ESP_LOGI(TAG, "Checksum failure %4X %4X %2X\n", temp, rh, checksum);
        return 0;
    }
    // 返回数据
    
    rh = rh >> 8;
    temp = (temp >> 8) * 10 + (temp & 0xFF);

    //判断数据合法性
    if(rh <= 100)
        *humidity = rh;
    if(temp <= 600)
        *temp_x10 = temp;
    return 1;
}


/** 获取DHT11数据
 * @param temp_x10 温度值
 * @return 无
*/
int DHT11_StartGet(int *temp_x10, int *humidity)
{
    //发送20ms开始信号脉冲启动DHT11单总线
    gpio_set_direction(DHT11_IO, GPIO_MODE_OUTPUT);
    gpio_set_level(DHT11_IO, 1);
    ets_delay_us(1000);
    gpio_set_level(DHT11_IO, 0);
    ets_delay_us(20000);
    //拉高20us
    gpio_set_level(DHT11_IO, 1);
    ets_delay_us(20);
    //信号线设置为输入准备接收数据
    gpio_set_direction(DHT11_IO, GPIO_MODE_INPUT);
    gpio_set_pull_mode(DHT11_IO,GPIO_PULLUP_ONLY);

    //启动RMT接收器以获取数据
    rmt_receive_config_t receive_config = {
        .signal_range_min_ns = 100,     //最小脉冲宽度(0.1us),信号长度小于这个值，视为干扰
        .signal_range_max_ns = 1000*1000,     //最大脉冲宽度(1000us)，信号长度大于这个值，视为结束信号
    };
    
    static rmt_symbol_word_t raw_symbols[128];    //接收缓存
    static rmt_rx_done_event_data_t rx_data;    //实际接收到的数据
    ESP_ERROR_CHECK(rmt_receive(rx_chan_handle, raw_symbols, sizeof(raw_symbols), &receive_config));
    
    // wait for RX done signal
    if (xQueueReceive(rx_receive_queue, &rx_data, pdMS_TO_TICKS(1000)) == pdTRUE) {
        // parse the receive symbols and print the result
        return parse_items(rx_data.received_symbols, rx_data.num_symbols,humidity, temp_x10);
    }
    return 0;
}

DHT.h文件

#ifndef _DHT11_H_
#define _DHT11_H_
#include <stdint.h>

/** DHT11初始化
 * @param dht11_pin GPIO引脚
 * @return 无
*/
void DHT11_Init();

/** 获取DHT11数据
 * @param temp_x10 温度值X10
 * @param humidity 湿度值
 * @return 无
*/
int DHT11_StartGet(int *temp_x10, int *humidity);

#endif