[STM32 learning] (15) STM32 realizes DHT11 temperature and humidity acquisition and display

Have a look first DHT11 The appearance of temperature and humidity .

DHT11 It is a wet temperature integrated digital sensor produced by Guangzhou Aosong Co., Ltd . The sensor consists of a resistive humidity measuring element and a NTC Temperature measuring element , And with a high performance 8 Bit single chip microcomputer connected . Through the simple circuit connection of MCU and other microprocessors, we can collect local humidity and temperature in real time . DHT11 Simple single bus can be used to communicate with MCU , Just one I/O mouth . Sensor internal humidity and temperature data 40Bit The data is transmitted to the single chip microcomputer at one time , The data is verified by checksum , Effectively ensure the accuracy of data transmission . DHT11 Low power consumption , 5V At supply voltage , Average maximum operating current 0.5mA.
 

Operating voltage range ：3.3V-5.5V

Working current ： Average 0.5mA

Output ： Single bus digital signal

measuring range ： humidity 20~90％RH, temperature 0~50℃

precision ： humidity ±5%, temperature ±2℃

The resolution of the ： humidity 1%, temperature 1℃ 

DHT11 The digital wet temperature sensor adopts single bus data format . A single data pin port completes the bidirectional transmission of input and output .

Its data packet consists of 5Byte（40Bit） form . The data is divided into decimal part and integer part , A complete data transfer is 40bit, High first out .

DHT11 The data format of is ：8bit Humidity integer data +8bit Humidity decimal data +8bit Temperature integer data +8bit Temperature decimal data +8bit The checksum .

among The checksum data is the sum of the first four bytes . The sensor data output is uncoded binary data . data ( humidity 、 temperature 、 Integers 、 decimal ) Should be handled separately .

The sensor data output is uncoded binary data . data ( humidity 、 temperature 、 Integers 、 decimal ) Should be handled separately .
 

DHT11 Start sending data flow

After the host sends the start signal , Delay waiting for 20us-40us Post read DH11T Your response signal , The read bus is low , explain DHT11 Send a response signal , DHT11 After sending the response signal , Then pull up the bus , Prepare to send data , each bit The data starts at a low level , The format is shown in the figure below . If the read response signal is high , be DHT11 No response , Please check whether the line is connected properly .

First, the host sends a start signal , namely ： Pull down the data line , keep t1（ At least 18ms） Time , Then pull up the data cable t2（20~40us） Time , Then read DHT11 Response , Normal word ,DHT11 Will pull down the data cable , keep t3（40~50us） Time , As a response signal , then DHT11 Pull up the data line , Protect t4（40~50us） After time , Start outputting data .
Host reset signal and DHT11 response signal

Numbers ‘ 0’ Signal representation

 

The program should distinguish data 0 And data 1 The format of ： First judge the level state of the pin at this time , If it is low level, it will keep waiting , Until the high level appears , Delay after high level appears 40us, And read the level state after delay , If it is high , Then the data is 1, Otherwise 0

The transmission is over 40 After bit data , The sensor outputs another 50us After the low level of , Release the data bus , The acquisition process ends .

The code is as follows ：

The selected single chip microcomputer model ：STM32L052K8*      In fact, it doesn't matter which MCU , Mainly the realization of temperature and humidity module

connection ：PA6 Connected to the DATA On the mouth

The code is as follows ：

DHT11.c

#include "dht11.h"

static GPIO_InitTypeDef  GPIO_InitStruct;

uint8_t  U8FLAG,k;
uint8_t  U8count,U8temp;
uint8_t  U8T_data_H,U8T_data_L,U8RH_data_H,U8RH_data_L,U8checkdata;
uint8_t  U8T_data_H_temp,U8T_data_L_temp,U8RH_data_H_temp,U8RH_data_L_temp,U8checkdata_temp;
uint8_t  U8comdata;

void delay_us(uint16_t j)  // Microsecond delay   
{      
	uint8_t i;
	for(;j>0;j--)
	{ 	
		for(i=0;i<8;i++);
	}
}

void delay_ms(uint16_t j) // Millisecond delay  
{      
	uint16_t i;
	for(;j>0;j--)
	{ 	
		for(i=0;i<8000;i++);

	}
}

void DHT11_INIT(void)  // configure port PA6
{
	__HAL_RCC_GPIOB_CLK_ENABLE();

	GPIO_InitStruct.Pin = DHT11_SDA;
	GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
	GPIO_InitStruct.Pull = GPIO_NOPULL;
	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH  ;

	HAL_GPIO_Init(DHT11_COM, &GPIO_InitStruct); 

}

void  COM(void)   // start-up   Read 
{
	uint8_t i;        
	for(i=0;i<8;i++)	   
	{
		U8FLAG=2;	  // Initialization number 
		while((!DHT11_SDA_READ())&&U8FLAG++);  // Read port acquisition , Low level indicates starting signal 
		delay_us(10);
		delay_us(10);
		delay_us(10); // wait for 
		U8temp=0;
		if(DHT11_SDA_READ())U8temp=1; // There are data to 
		U8FLAG=2;
		while((DHT11_SDA_READ())&&U8FLAG++);  // Read  
		if(U8FLAG==1)break; 
		U8comdata<<=1;
		U8comdata|=U8temp;
	 }

}


void RH(void)   //
{
	DHT11_SDA_L(); // Pull it down 
	delay_ms(18);
	DHT11_SDA_H(); // pull up 
	delay_us(10);
	delay_us(10);
	delay_us(10);
	delay_us(10);	// wait for 
	if(!DHT11_SDA_READ()) // Low level entry 
	{
		U8FLAG=2;
		while((!DHT11_SDA_READ())&&U8FLAG++);// Data waiting 
		U8FLAG=2;
		while((DHT11_SDA_READ())&&U8FLAG++);	// start-up  
		COM();												//
		U8RH_data_H_temp=U8comdata; 	// Read humidity high 
		COM();
		U8RH_data_L_temp=U8comdata;	// Read the low humidity 
		COM();
		U8T_data_H_temp=U8comdata;		// Read the high temperature 
		COM();
		U8T_data_L_temp=U8comdata;		// Read the low temperature 
		COM();
		U8checkdata_temp=U8comdata;  // Check bit 

		DHT11_SDA_H();

		U8temp=(U8T_data_H_temp+U8T_data_L_temp+U8RH_data_H_temp+U8RH_data_L_temp);//40 Bit data addition 
		if(U8temp==U8checkdata_temp)  // data verification   contrast 
		{
			U8RH_data_H=U8RH_data_H_temp; // Pay the read value 
			U8RH_data_L=U8RH_data_L_temp;
			U8T_data_H=U8T_data_H_temp;
			U8T_data_L=U8T_data_L_temp;
			U8checkdata=U8checkdata_temp;
		}
	}
}
	

DHT11.h

#ifndef __DHT11_H
#define __DHT11_H

/* Includes ------------------------------------------------------------------*/
#include "stm32l0xx_hal.h"

#define   Data_0_time    4

#define DHT11_SDA GPIO_PIN_6
#define DHT11_COM GPIOA

#define DHT11_SDA_H() HAL_GPIO_WritePin(DHT11_COM,DHT11_SDA,GPIO_PIN_SET)
#define DHT11_SDA_L() HAL_GPIO_WritePin(DHT11_COM,DHT11_SDA,GPIO_PIN_RESET)

#define DHT11_SDA_READ() HAL_GPIO_ReadPin(DHT11_COM,DHT11_SDA)  // Macro definition read data 

extern uint8_t  U8T_data_H,U8T_data_L,U8RH_data_H,U8RH_data_L,U8checkdata;

void delay_us(uint16_t j);
void delay_ms(uint16_t j);
void DHT11_INIT(void);
void  COM(void);
void RH(void);


#endif /* __DHT11_H */


/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

My implementation is realized through serial port , The configuration information of the serial port is also very simple , The code information of the serial port is not posted here , The effect is as follows ：