STM32 summary (HAL Library) - DHT11 temperature sensor (intelligent safety assisted driving system)

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 that the product has 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 factor exists in the form of a program OTP In the memory , These calibration coefficients should be called in the process of detecting the model inside the sensor . Single line serial interface , Make system integration easy and fast . Super small size 、 Very low power consumption , Make it the best choice for even the most demanding applications . Products for 4 Single row pin package , Easy to connect .

DHT11 working principle

2.1、DHT11data data format ： （ High first out ）

Primary transmission 40 Bit data =8bit Humidity integer data + 8bit Humidity decimal data + 8bit Temperature integer data + 8bit Temperature decimal data + 8bit The checksum . When the data transmission is correct , The checksum data is equal to “8bit Humidity integer data +8 Humidity decimal data +8bit Temperature integer data +8bit Temperature decimal data ” The end of the result 8 position .

user MCU After sending a start signal ,DHT11 Switch from low power consumption to high speed mode , Wait for the end of the host start signal ,DHT11 Send a response signal , Send out 40bit The data of , And trigger a signal acquisition , Users can choose to read some data , From mode ,DHT11 Receive the start signal to trigger a temperature and humidity acquisition , If no start signal is received from the host ,DHT11 Do not actively collect temperature and humidity , After collecting data, switch to low speed mode .

2.2、 Sequential programming

Starting timing

The bus idle state is high , The host pulls down the bus and waits DHT11 Respond to , The host must pull the bus lower than 18 millisecond , Guarantee DHT11 Can detect the start signal .DHT11 After receiving the start signal from the host , Wait for the host start signal to end , And then send 80us Low level response signal . After the host sends the start signal , Delay waiting for 20-40us after , Read DHT11 The response signal , After the host sends the start signal , You can switch to input mode , Or the average output high power can , The bus is pulled up by a pull-up resistor .

Data receiving timing

The bus is low , explain DHT11 Send a response signal ,DHT11 After sending the response signal , Then pull up the bus 80us, Prepare to send data , each bit All the data are based on 50us The low level slot starts , The length of the high level determines that the data bit is 0 still 1. 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 . When the last one bit After the data is transmitted ,DHT11 Pull down the bus 50us, Then, the bus is pulled up by the pull-up resistance and enters the idle state .

Numbers 0 Signal representation

Numbers 1 Signal representation

*DHT11 Code

3、DHT11 Communication process and code
3.1、 Simple communication process

Step 1 initialization IO mouth Complete the starting sequence Check DHT11 Whether there is

The signal line of the second host is pulled up to receive data , Receive... In turn 40 position

3.2 The main program part

dht11.c Part of the code *

#include "delay.h"
#include "dht11.h"
#include "tim.h"


#define DHT11_DQ_IN HAL_GPIO_WritePin(GPIOC, DHT11_DATA_OUT_Pin, GPIO_PIN_SET) // Input 

// initialization DHT11, At the same time, check whether it is connected DHT11,PA11 initialization 
 	 
uint8_t DHT11_Init(void)
{
    	 
  GPIO_InitTypeDef GPIO_InitStruct = {
    0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();


  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, DHT11_DATA_OUT_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = DHT11_DATA_OUT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(DHT11_DATA_OUT_GPIO_Port, &GPIO_InitStruct);	

	DHT11_Rst();  
	return DHT11_Check();
}      
// Reset DHT11
void DHT11_Rst(void)	   
{
                     
	DHT11_IO_OUT(); 	//SET OUTPUT
	HAL_GPIO_WritePin(GPIOC, DHT11_DATA_OUT_Pin, GPIO_PIN_RESET); 	// Pull it down 
	DelayXms(20);    	// Lower the delay at least 18ms
	HAL_GPIO_WritePin(GPIOC, DHT11_DATA_OUT_Pin, GPIO_PIN_SET); 	//DQ=1, pull up  
	DelayUs(30);     	// Raise the delay at least 20~40us
}
 
// Test response 
// return 1： Detect errors 
// return 0： Test successful 
uint8_t DHT11_Check(void) 	   
{
       
	uint8_t retry=0;
	DHT11_IO_IN();//SET INPUT 
    while (HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_0)&&retry<100)//DHT11 Pull it down 40~80us
	{
    
		retry++;
		DelayUs(1);
	};	 
	if(retry>=100)return 1;
	else retry=0;
    while (!HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_0)&&retry<100)//DHT11 Pull up again 40~80us
	{
    
		retry++;
		DelayUs(1);
	};
	if(retry>=100)return 1;	    
	return 0;
}
 
// Read a bit Bit
// return 1 or 0
uint8_t DHT11_Read_Bit(void) 			 
{
    
 	uint8_t retry=0;
	while(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_0)&&retry<100)// Wait for low level 
	{
    
		retry++;
		DelayUs(1);
	}
	retry=0;
	while(!HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_0)&&retry<100)// Wait for high level 
	{
    
		retry++;
		DelayUs(1);
	}
	DelayUs(40);// wait for 40us
	if(HAL_GPIO_ReadPin(GPIOC, GPIO_PIN_0))return 1;
	else return 0;		   
}
 
// Read a byte 
// Returns the data read 
uint8_t DHT11_Read_Byte(void)    
{
            
	uint8_t i,dat;
	dat=0;
	for (i=0;i<8;i++) 
	{
    
		dat<<=1; 
		dat|=DHT11_Read_Bit();
	}						    
	return dat;
}
 
//DHT11 Read data once 
//temp: temperature ( Range :0~50°)
//humi: humidity ( Range :20%~90%)
//tem： Temperature decimal places 
//hum： Humidity decimal places 
uint8_t DHT11_Read_Data(uint8_t *temp,uint8_t *humi,uint8_t *tem,uint8_t *hum)    
{
            
 	uint8_t buf[5];
	uint8_t i;
	DHT11_Rst();
	if(DHT11_Check()==0)
	{
    
		for(i=0;i<5;i++)// Read 40 Bit byte 
		{
    
			buf[i]=DHT11_Read_Byte();
		}
		if((buf[0]+buf[1]+buf[2]+buf[3])==buf[4])
		{
    
			*humi=buf[0];
			*hum=buf[1];
			*temp=buf[2];
			*tem=buf[3];
		}
	}
	else return 1;
	return 0;	    
}
 

//DHT11 Output mode configuration 
void DHT11_IO_OUT()	
{
    
  GPIO_InitTypeDef GPIO_InitStruct = {
    0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();


  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, DHT11_DATA_OUT_Pin, GPIO_PIN_SET);

  /*Configure GPIO pin : PtPin */
  GPIO_InitStruct.Pin = DHT11_DATA_OUT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(DHT11_DATA_OUT_GPIO_Port, &GPIO_InitStruct);
}
 
//DHT11 Input mode configuration 
void DHT11_IO_IN(void)	
{
    
  GPIO_InitTypeDef GPIO_InitStruct = {
    0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  /*Configure GPIO pin : PC0 */
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
}
dht11.h Part of the code 

```c
#ifndef _DHT11_H_
#define _DHT11_H_
#include "main.h"
#define DHT11_DATA_OUT_Pin GPIO_PIN_0
#define DHT11_DATA_OUT_GPIO_Port GPIOC

void DHT11_Rst(void);
uint8_t DHT11_Check(void);
uint8_t DHT11_Read_Bit(void);
uint8_t DHT11_Read_Byte(void);
uint8_t DHT11_Read_Data(uint8_t *temp,uint8_t *humi,uint8_t *tem,uint8_t *hum);
uint8_t DHT11_Init(void);
void DHT11_IO_IN(void);
void DHT11_IO_OUT();
#endif

mian.c Code 

```c
/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2022 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "tim.h"
#include "usart.h"
#include "gpio.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "dht11.h"
#include "delay.h"
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM6_Init();
  MX_TIM7_Init();
  MX_USART1_UART_Init();
  MX_USART2_UART_Init();
  MX_USART3_UART_Init();
  /* USER CODE BEGIN 2 */
	Delay_Init();
	uint8_t temperature;         
	uint8_t humidity; 
	uint8_t temp;         
	uint8_t humi; 
	uint8_t rx_buf[5];
	DHT11_Init();                         //DHT11 initialization        Pin PA4PA6-MISO PA7-MOSI 


  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
		DHT11_Read_Data(&temperature,&humidity,&temp,&humi);
		rx_buf[0]=temperature;
		rx_buf[1]=humidity;
    printf("temp=%d,humi=%d\r\n",rx_buf[0],rx_buf[1]);		  
		DelayXms(5000);
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

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

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