This project is a driver library for the DHT 11 temperature and humidity sensor based on the STM32 hal library.
- Projects developed using the STM32 hal library
- Using DHT11 for your Projects
- Configure clocks and timers in STM32CubeMX, ensuring that one of the available timer frequencies is set to
$1\mathrm{MHz}$ .(default timer is tim2htim2) - Modify the macro definitions in dht11.h to make sure you are using the correct PIN.(default PIN is GPIOB PIN_4)
- Copy the four files
delay.h dht11.h delay.c dht11.cto the appropriate location in your project. - Considering the communication interval of DHT11 module, the interval reading time after successful reading is set (default is 30s). You can modify the macro definition
DHT_READ_INTERVALindht11.has required - The value read is stored in the global variable
data[], which you can access viaextern uint8_t Data[5];.
void delayus(uint16_t us)
Used to achieve microsecond delays. Make sure your timer has a frequency of
void delayus(uint16_t us)
{
uint16_t differ = 0xffff-us-5;
__HAL_TIM_SET_COUNTER(&htim2,differ); //Set TIM2 counter start value
HAL_TIM_Base_Start(&htim2); //Run TIM2
while(differ < 0xffff-5){
differ = __HAL_TIM_GET_COUNTER(&htim2); //Query the count value of the counter
}
HAL_TIM_Base_Stop(&htim2);
}uint8_t DHT_Read(void)
Reads the value of the sensor and places it in a global variable Data[]. Data[0] is humidity integer and Data[1] is humidity decimal.Data[3] is temperature integer and Data[4] is temperature decimal.
uint8_t DHT_Read(void)
{
static uint32_t last_read_time = 0;
uint32_t current_time = HAL_GetTick();
// Check if a sufficient reading interval has passed
if (((current_time - last_read_time) < DHT_READ_INTERVAL)&&(Success==1)) {
return 2;
}
else {
last_read_time = current_time;
}
uint8_t retry=0;
uint8_t i;
DHT_GPIO_SET_OUTPUT();
HAL_GPIO_WritePin(DHT_GPIO_PORT,DHT_DATA_PIN,GPIO_PIN_RESET);
HAL_Delay(18);
HAL_GPIO_WritePin(DHT_GPIO_PORT,DHT_DATA_PIN,GPIO_PIN_SET);
delayus(20);
DHT_GPIO_SET_INPUT();
delayus(20);
if(HAL_GPIO_ReadPin(DHT_GPIO_PORT,DHT_DATA_PIN)==0)
{
while(HAL_GPIO_ReadPin(DHT_GPIO_PORT,DHT_DATA_PIN)==0 && retry<100)
{
delayus(1);
retry++;
}
retry=0;
while(HAL_GPIO_ReadPin(DHT_GPIO_PORT,DHT_DATA_PIN)==1 && retry<100)
{
delayus(1);
retry++;
}
retry=0;
for(i=0; i<5; i++)
{
Data[i] = DHT_Read_Byte(); //Read a byte for each loop
}
delayus(50);
// Description: Data[0] humidity, Data[2] temperature. data[1] and data[3] are decimal places of 0 and // 2 respectively. data[4] is used for checksum.
}
uint32_t sum=Data[0]+Data[1]+Data[2]+Data[3]; //check
if((sum)==Data[4]) { Success=1; return 1; }
else { Success=0; return 0; }
}
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