RT-Thread-CPK-RA2L1评估板DHT11（3）RT-Thread问答社区

CPK-RA2L1评估板DHT11（3）

发布于 2023-03-12 20:05:48 浏览：347 订阅该版

[tocm]

# 一、准备
本篇文章主要介绍使用RT-Thread Studio 和瑞萨 CPK-RA2L1评估板，使用大佬的轮子采集温湿度

# 二、硬件准备
CPK-RA2L1评估板, 这个板子的芯片型号是 R7FA2L1AB2DFM，DHT11 温湿度传感器。
![1.png](https://oss-club.rt-thread.org/uploads/20230312/ac6443cd567ba12171f67742f7c6c18a.png.webp)

# 三、新建工程
参考：[https://club.rt-thread.org/ask/article/7ef4e81b9075c00f.html]
需要注意这个DHT11的通信时序，此处把datasheet上传了
[DHT11 温湿度传感器变送器 探头.pdf](https://club.rt-thread.org/file_download/5fe15e929e206118)
1、总线空闲状态为高电平,主机把总线拉低等待DHT11响应,主机把总线拉低必须大于18毫秒,保证DHT11能检测到起始信号。DHT11接收到主机的开始信号后,等待主机开始信号结束,然后发送80us低电平响应信号.主机发送开始信号结束后,延时等待20-40us后, 读取DHT11的响应信号,主机发送开始信号后,可以切换到输入模式,或者输出高电平均可, 总线由上拉电阻拉高。
![2.png](https://oss-club.rt-thread.org/uploads/20230312/26d638017b6e241e7cab4b6a386c3cd1.png.webp)
2、总线为低电平,说明DHT11发送响应信号,DHT11发送响应信号后,再把总线拉高80us,准备发送数据,每一bit数据都以50us低电平时隙开始,高电平的长短定了数据位是0还是1.格式见下面图示.如果读取响应信号为高电平,则DHT11没有响应,请检查线路是否连接正常.当最后一bit数据传送完毕后，DHT11拉低总线50us,随后总线由上拉电阻拉高进入空闲状态
![3.png](https://oss-club.rt-thread.org/uploads/20230312/f1f4b28f9968a9e6ee21afeea962c7d0.png.webp)
3、数字0信号
![4.png](https://oss-club.rt-thread.org/uploads/20230312/1c12a0f66343493af0c3927fbcd1f989.png.webp)
4、数字1信号
![5.png](https://oss-club.rt-thread.org/uploads/20230312/0fc0350a6acf2b1c6caf0bf728606eca.png.webp)

四、驱动代码

```c
/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2023-03-01     DYC       the first version
 */

#include "dht11.h"
#include <stdio.h>
#include "hal_data.h"
#include <board.h>

#define DBG_TAG                  "sensor.asair.dhtxx"
#ifdef PKG_USING_DHTXX_DEBUG
#define DBG_LVL                  DBG_LOG
#else
#define DBG_LVL                  DBG_ERROR
#endif
#include <rtdbg.h>

/* timing */
#define DHT1x_BEGIN_TIME         20  /* ms */
#define DHT2x_BEGIN_TIME         1   /* ms */
#define DHTxx_PULL_TIME          30  /* us */
#define DHTxx_REPLY_TIME         100 /* us */
#define MEASURE_TIME             40  /* us */

RT_WEAK void rt_hw_us_delay(rt_uint32_t us)
{
    rt_uint32_t delta;

us = us * (SysTick->LOAD / (1000000 / RT_TICK_PER_SECOND));
    delta = SysTick->VAL;

while (delta - SysTick->VAL < us) continue;
}

/**
 * This function will split a number into two part according to times.
 *
 * @param num      the number will be split
 * @param integer  the integer part
 * @param decimal  the decimal part
 * @param times    how many times of the real number (you should use 10 in this case)
 *
 * @return 0 if num is positive, 1 if num is negative
 */
int split_int(const int num, int *integer, int *decimal, const rt_uint32_t times)
{
    int flag = 0;
    if (num < 0) flag = 1;

int anum = num<0 ? -num : num;
    *integer = anum / times;
    *decimal = anum % times;

return flag;
}

/**
 * This function will convert temperature in degree Celsius to Kelvin.
 *
 * @param c  the temperature indicated by degree Celsius
 *
 * @return the result
 */
float convert_c2k(float c)
{
    return c + 273.15;
}

/**
 * This function will convert temperature in degree Celsius to Fahrenheit.
 *
 * @param c  the temperature indicated by degree Celsius
 *
 * @return the result
 */
float convert_c2f(float c)
{
    return c * 1.8 + 32;
}

/**
 * This function will convert temperature in degree Fahrenheit to Celsius.
 *
 * @param f  the temperature indicated by degree Fahrenheit
 *
 * @return the result
 */
float convert_f2c(float f)
{
    return (f - 32) * 0.55555;
}

/**
 * This function will read a bit from sensor.
 *
 * @param pin  the pin of Dout
 *
 * @return the bit value
 */
static uint8_t dht_read_bit(const rt_base_t pin)
{
    uint8_t retry = 0;

while(rt_pin_read(pin) && retry < DHTxx_REPLY_TIME)
    {
        retry++;
        rt_hw_us_delay(1);
    }

retry = 0;
    while(!rt_pin_read(pin) && retry < DHTxx_REPLY_TIME)
    {
        retry++;
        rt_hw_us_delay(1);
    }

rt_hw_us_delay(MEASURE_TIME);

return rt_pin_read(pin);
}

/**
 * This function will read a byte from sensor.
 *
 * @param pin  the pin of Dout
 *
 * @return the byte
 */
static uint8_t dht_read_byte(const rt_base_t pin)
{
    uint8_t i, byte = 0;

for(i=0; i<8; i++)
    {
        byte <<= 1;
        byte |= dht_read_bit(pin);
    }

return byte;
}

/**
 * This function will read and update data array.
 *
 * @param dev  the device to be operated
 *
 * @return RT_TRUE if read successfully, otherwise return RT_FALSE.
 */
rt_bool_t dht_read(dht_device_t dev)
{
    RT_ASSERT(dev);

uint8_t i, retry = 0, sum = 0;

#ifdef PKG_USING_DHTXX_INTERRUPT_DISABLE
    rt_base_t level;
#endif

/* Reset data buffer */
    rt_memset(dev->data, 0, DHT_DATA_SIZE);

/* MCU request sampling */
    rt_pin_mode(dev->pin, PIN_MODE_OUTPUT);
    rt_pin_write(dev->pin, PIN_LOW);

if (dev->type == DHT11) {
        rt_thread_mdelay(DHT1x_BEGIN_TIME);        /* Tbe */
    } else {
        rt_thread_mdelay(DHT2x_BEGIN_TIME);
    }

#ifdef PKG_USING_DHTXX_INTERRUPT_DISABLE
    level = rt_hw_interrupt_disable();
#endif

rt_pin_mode(dev->pin, PIN_MODE_INPUT_PULLUP);
    rt_hw_us_delay(DHTxx_PULL_TIME);               /* Tgo */

/* Waiting for sensor reply */
    while (rt_pin_read(dev->pin) && retry < DHTxx_REPLY_TIME)
    {
        retry++;
        rt_hw_us_delay(1);                         /* Trel */
    }
    if(retry >= DHTxx_REPLY_TIME) return RT_FALSE;

retry = 0;
    while (!rt_pin_read(dev->pin) && retry < DHTxx_REPLY_TIME)
    {
        retry++;
        rt_hw_us_delay(1);                         /* Treh */
    };
    if(retry >= DHTxx_REPLY_TIME) return RT_FALSE;

/* Read data */
    for(i=0; i<DHT_DATA_SIZE; i++)
    {
        dev->data[i] = dht_read_byte(dev->pin);
    }

#ifdef PKG_USING_DHTXX_INTERRUPT_DISABLE
    rt_hw_interrupt_enable(level);
#endif

/* Checksum */
    for(i=0; i<DHT_DATA_SIZE-1; i++)
    {
        sum += dev->data[i];
    }
    if(sum != dev->data[4]) return RT_FALSE;

return RT_TRUE;
}

/**
 * This function will get the humidity from dhtxx sensor.
 *
 * @param dev  the device to be operated
 *
 * @return the humidity value
 */
rt_int32_t dht_get_humidity(dht_device_t const dev)
{
    RT_ASSERT(dev);

rt_int32_t humi = 0;

switch(dev->type)
    {
    case DHT11:
        humi = dev->data[0] * 10 + dev->data[1];
        break;
    default:
        break;
    }

return humi;
}

/**
 * This function will get the temperature from dhtxx sensor.
 *
 * @param dev  the device to be operated
 *
 * @return the temperature value
 */
rt_int32_t dht_get_temperature(dht_device_t const dev)
{
    RT_ASSERT(dev);

rt_int32_t temp = 0;

switch(dev->type)
    {
    case DHT11:
        temp = dev->data[2] * 10 + (dev->data[3] & 0x7f);
        if(dev->data[3] & 0x80) {
            temp = -temp;
        }
        break;
    default:
        break;
    }

return temp;
}

/**
 * This function will init dhtxx sensor device.
 *
 * @param dev  the device to init
 * @param pin  the pin of Dout
 *
 * @return the device handler
 */
rt_err_t dht_init(struct dht_device *dev, const rt_base_t pin)
{
    if(dev == NULL)
        return -RT_ERROR;

dev->type = DHT_TYPE;
    dev->pin  = pin;

rt_memset(dev->data, 0, DHT_DATA_SIZE);
    rt_pin_mode(dev->pin, PIN_MODE_INPUT_PULLUP);

return RT_EOK;
}

// 1、初始化类型
dht_device_t dht_create(const rt_base_t pin)
{
    dht_device_t dev;

dev = rt_calloc(1, sizeof(struct dht_device));
    if (dev == RT_NULL)
    {
        LOG_E("Can't allocate memory for dhtxx device");
        return RT_NULL;
    }

dev->type = DHT_TYPE;
    dev->pin  = pin;

rt_memset(dev->data, 0, DHT_DATA_SIZE);
    rt_pin_mode(dev->pin, PIN_MODE_INPUT_PULLUP);

return dev;
}

void dht_delete(dht_device_t dev)
{
    if (dev)
        rt_free(dev);
}

```

```c
/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2023-03-01     DYC       the first version
 */
#ifndef SRC_DHT11_H_
#define SRC_DHT11_H_

#include <stdio.h>
#include <rthw.h>
#include <rtdevice.h>
#include <board.h>

#include <rtthread.h>

#define DHTLIB_VERSION                       "0.9.0"
#define DHT_DATA_SIZE                        5

/* sensor model type */
#define DHT11                                0

#define DHT_TYPE                             DHT11

struct dht_device
{
    rt_base_t   pin;
    rt_uint8_t  type;
    rt_uint8_t  data[DHT_DATA_SIZE];
    rt_mutex_t  lock;
};

typedef struct dht_device *dht_device_t;

dht_device_t dht_create(const rt_base_t pin);
void dht_delete(dht_device_t dev);

rt_err_t   dht_init(struct dht_device *dev, const rt_base_t pin);
rt_bool_t  dht_read(dht_device_t dev);
rt_int32_t dht_get_humidity(dht_device_t dev);
rt_int32_t dht_get_temperature(dht_device_t dev);

float convert_c2k(float c);//将摄氏温度转为开氏温度
float convert_c2f(float c);//将摄氏温度转为华氏温度
float convert_f2c(float f);//将华氏温度转为摄氏温度

rt_int32_t split_int(const rt_int32_t num, rt_int32_t *integer,
                     rt_int32_t *decimal, const rt_uint32_t times);

rt_err_t rt_hw_dht_init(const char *name, struct rt_sensor_config *cfg);

#endif /* SRC_DHT11_H_ */

```

这里DHT11 使用的是 GPIO 0208,所以需要把这个引脚配置为输入模式

![6.png](https://oss-club.rt-thread.org/uploads/20230312/06abdaa2987974b86809ea628866c3e4.png)

五、烧录验证

![7.png](https://oss-club.rt-thread.org/uploads/20230312/695a63b61a73741d487a328aacfa40b6.png)