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Stm32+dht11 reading temperature and humidity data display

2022-07-21 05:57:00 【InfoQ】

One 、 Introduction to the environment

MCU:

STM32F103C8T6

Temperature and humidity module :

DHT11

Development software :

Keil5

Two 、DHT11 Introduce

DHT11 Digital temperature and humidity sensor is a temperature and humidity composite sensor with calibrated digital signal output .

It uses special digital module acquisition technology and temperature and humidity sensing technology , Ensure high reliability and excellent long-term stability . The sensor consists of a resistive humidity sensor and a NTC Temperature measuring element , And with a high performance 8 Bit single chip microcomputer connected . So this product has excellent quality 、 Super quick response 、 Strong anti-interference ability 、 High cost performance advantages .

Every DHT11 Sensors are calibrated in a very accurate humidity calibration room . The calibration coefficients are stored in the form of a program OTP In the memory , These calibration coefficients are called in the process of signal processing inside the sensor .

Single line serial interface , Make system integration easy and fast . Super small size 、 Very low power consumption , The signal transmission distance can reach 20 Meters above , Make it the best choice for all kinds of applications and even the most demanding applications .

Products for 4 Single row pin package . Easy to connect , Special packaging forms can be provided according to user needs .

Application field

► HVAC

► Testing and testing equipment

► automobile

► data logger

► consumer goods

► Auto-Control

► weather station

► Home appliance

► Humidity regulator

► Medical care

► Dehumidifier

3、 ... and 、 Core code

3.1 dht11.c

#include &quot;dht11.h&quot;
#include &quot;delay.h&quot;

// Reset DHT11
void DHT11_Rst(void) 
{ 
 DHT11_IO_OUT(); //SET OUTPUT
 DHT11_DQ_OUT=0; // Pull it down DQ
 DelayMs(20); // Pull down at least 18ms
 DHT11_DQ_OUT=1; //DQ=1 
 DelayUs(30); // The main engine is pulled up 20~40us
}


// wait for DHT11 The response of the 
// return 1: Not detected DHT11 The existence of 
// return 0: There is 
u8 DHT11_Check(void) 
{ 
 u8 retry=0;
 DHT11_IO_IN();//SET INPUT 
 while (DHT11_DQ_IN&&retry<100)//DHT11 Will pull down 40~80us
 {
 retry++;
 DelayUs(1);
 }; 
 if(retry>=100)return 1;
 else retry=0;
 while (!DHT11_DQ_IN&&retry<100)//DHT11 After pulling down, it will pull up again 40~80us
 {
 retry++;
 DelayUs(1);
 };
 if(retry>=100)return 1; 
 return 0;
}

// from DHT11 Read a bit 
// Return value ：1/0
u8 DHT11_Read_Bit(void) 
{
 u8 retry=0;
 while(DHT11_DQ_IN&&retry<100)// Wait until it goes low 
 {
 retry++;
 DelayUs(1);
 }
 retry=0;
 while(!DHT11_DQ_IN&&retry<100)// Wait for high level 
 {
 retry++;
 DelayUs(1);
 }
 DelayUs(40);// wait for 40us
 if(DHT11_DQ_IN)return 1;
 else return 0; 
}


// from DHT11 Read a byte 
// Return value ： Data read 
u8 DHT11_Read_Byte(void) 
{ 
 u8 i,dat;
 dat=0;
 for (i=0;i<8;i++) 
 {
 dat<<=1; 
 dat|=DHT11_Read_Bit();
 } 
 return dat;
 }


// from DHT11 Read data once 
//temp: Temperature value ( Range :0~50°)
//humi: Humidity value ( Range :20%~90%)
// Return value ：0, normal ;1, Read failed 
u8 DHT11_Read_Data(u8 *temp,u8 *humi) 
{ 
 u8 buf[5];
 u8 i;
 DHT11_Rst();
 if(DHT11_Check()==0)
 {
 for(i=0;i<5;i++)// Read 40 Bit data 
 {
 buf[i]=DHT11_Read_Byte();
 }
 if((buf[0]+buf[1]+buf[2]+buf[3])==buf[4])
 {
 *humi=buf[0];
 *temp=buf[2];
 }
 }else return 1;
 return 0; 
}


// initialization DHT11 Of IO mouth  DQ  Simultaneous detection DHT11 The existence of 
// return 1: non-existent 
// return 0: There is  
u8 DHT11_Init(void)
{
 RCC->APB2ENR|=1<<2; // Can make PORTA Port clock  
 GPIOA->CRL&=0XFF0FFFFF;//PORTA.11  Push pull output 
 GPIOA->CRL|=0X00300000;
 GPIOA->ODR|=1<<5; // Output 1 
 DHT11_Rst();
 return DHT11_Check();
}

3.2 dht11.h

#ifndef __DHT11_H
#define __DHT11_H 
#include &quot;sys.h&quot; 
 
//IO Direction setting 
#define DHT11_IO_IN() {GPIOA->CRL&=0XFF0FFFFF;GPIOA->CRL|=0x00800000;}
#define DHT11_IO_OUT() {GPIOA->CRL&=0XFF0FFFFF;GPIOA->CRL|=0x00300000;}

////IO Operation function  
#define DHT11_DQ_OUT PAout(5) // Data port  PA5
#define DHT11_DQ_IN PAin(5) // Data port  PA5


u8 DHT11_Init(void); // initialization DHT11
u8 DHT11_Read_Data(u8 *temp,u8 *humi);// Read the temperature and humidity 
u8 DHT11_Read_Byte(void); // Read a byte 
u8 DHT11_Read_Bit(void); // Read one bit 
u8 DHT11_Check(void); // Detect the presence of DHT11
void DHT11_Rst(void); // Reset DHT11 
#endif

3.3 main.c

#include &quot;stm32f10x.h&quot;
#include &quot;delay.h&quot;
#include &quot;led.h&quot;
#include &quot;sys.h&quot;
#include &quot;usart.h&quot;
#include <string.h>
#include <stdlib.h>
#include &quot;timer.h&quot;
#include &quot;adc.h&quot;
#include &quot;dht11.h&quot;

int main(void)
{
 u8 Temperature,Humidity;
 LED_Init(); // initialization LED
 USARTx_Init(USART1,72,115200);// A serial port 1 The initialization 
 DHT11_Init();
 
 while(1)
 {
 LED1=!LED1;
 if(DHT11_Read_Data(&Temperature,&Humidity) == 0)
 {
 printf(&quot; Temperature and humidity : %d,%d\n&quot;,Temperature,Humidity);
 }
 DelayMs(500);
 } 
}