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。
三、新建工程
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、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、数字0信号
4、数字1信号
四、驱动代码
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;
}
for(i=0; i {
sum += dev->data[i];
}
if(sum != dev->data[4]) return RT_FALSE;
return RT_TRUE;
}
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);
}
/
Copyright (c) 2006-2021, RT-Thread Development TeamSPDX-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
#include
#include
#include
#include
#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
五、烧录验证
