This is an example program to fetch data of DHT11 Sensors
Fork of DHT11_with_Nucleo by
main.cpp
- Committer:
- ledonger
- Date:
- 2017-04-05
- Revision:
- 12:31645d013d6c
- Parent:
- 11:1379308ecace
File content as of revision 12:31645d013d6c:
#include "mbed.h" //Tested with success on STM32 Nucleo L476 DigitalOut myled(LED1); // Activate LED DigitalIn mybutton(USER_BUTTON); // Activate button DigitalInOut data_pin(A0); // Activate digital in Serial pc(SERIAL_TX, SERIAL_RX); // Initialize UART connection // Use a terminal program (eg. TeraTerm). Timer tmr; //initialize timer uint64_t adat; // 64 bit variable for temporary data int i; // Function to initialize DHT11 void dht_read(void) { data_pin.output(); // Initialize measurement > 18 ms low data_pin = 0; wait_ms(20); // After high and release the pin switch input mode data_pin = 1; wait_us(20);//Wait for the sensor to take control and set low level /!\ Important data_pin.input(); // Wait until the end of 80 us low while(!data_pin.read()); // Wait until end of 80 us high while(data_pin.read()); // 40 bit, 40 read out cycle for(i=0; i<40; i++) { adat = adat << 1; // Shift for new number tmr.stop(); // Stop timer if runs tmr.reset(); // Reset timer // Wait until pin while(!data_pin.read()); tmr.start(); while(data_pin.read()); // If DHT11 HIGH longer than 40 micro seconds (hopefully 70 us) if(tmr.read_us() > 50) { // bit is 1 adat++; } } } int main() { pc.printf("Read the DHT11 temperature and humidity sensor!\n"); //Welcome message while(1) { if(mybutton == 0){ // Button is pressed // Reset adat variable adat = 0; myled = 1; // LED is ON dht_read(); // Call the function // Send result through UART result //pc.printf("Raw data:%10x\n\r",adat); pc.printf("Humidity:%d%%\n\r", (adat & 0x000000ff00000000) >> 32); // Humidity pc.printf("Temperature:%d degrees\n\r", (adat & 0x0000000000ff0000) >> 16 ); // Temperature if((adat&0x00000000000000ff) == ((adat&0x000000ff00000000) >> 32) + ((adat&0x00000000ff000000) >> 24) + ((adat&0x0000000000ff0000) >> 16) + ((adat&0x000000000000ff00) >> 8)){ pc.printf("Checksum : OK\n\r"); } else{ pc.printf("Checksum : Error\n\r"); } //pc.printf("Checksum:%d\n\r", adat & 0x00000000000000ff); // Checksum. /*pc.printf("Checksum calculated:%d\n\r",((adat&0x000000ff00000000) >> 32) + ((adat & 0x00000000ff000000) >> 24) + ((adat & 0x0000000000ff0000) >> 16) + ((adat & 0x000000000000ff00) >> 8));*/ wait_ms(300); // Wait 0.2 sec till continue. } else{ myled = 0; // LED is OFF } } }