Ro Led / Mbed 2 deprecated BLE_DHT11_Service_TemperatureHumidity

Project aiming to do a Bluetooth Low Energy IoT devices, which measure temperature and humidity. Bluetooth achieved with the IDB05A1 shield. Temperature/humidity achieved with a DHT11 sensor. Project working, tested on an STM32 L476 board.

Dependencies:   BLE_API X_NUCLEO_IDB0XA1 mbed

DHT11.h@1:023e1eae2048, 2017-04-18 (annotated)

Committer:
ledonger
Date:
Tue Apr 18 14:08:50 2017 +0000
Revision:
1:023e1eae2048
Parent:
0:d2c18f736df1 
Be careful to use mbed revision 125

Who changed what in which revision?

UserRevisionLine numberNew contents of line
ledonger 1:023e1eae2048 1 #ifndef DHT11_H
ledonger 1:023e1eae2048 2 #define DHT11_H
ledonger 0:d2c18f736df1 3
ledonger 0:d2c18f736df1 4 //Class to manage DHT11 sensor
ledonger 0:d2c18f736df1 5 class DHT11{
ledonger 0:d2c18f736df1 6
ledonger 0:d2c18f736df1 7 public:
ledonger 0:d2c18f736df1 8 /* Takes the data pin of the sensor in parameter */
ledonger 0:d2c18f736df1 9 DHT11(PinName pin):dataPin(pin)
ledonger 0:d2c18f736df1 10 {
ledonger 0:d2c18f736df1 11 iBit = 0;
ledonger 0:d2c18f736df1 12 data = 0;
ledonger 0:d2c18f736df1 13 }
ledonger 0:d2c18f736df1 14
ledonger 0:d2c18f736df1 15 /* Request and receive new data from sensor
ledonger 0:d2c18f736df1 16 Returns :
ledonger 0:d2c18f736df1 17 1 : OK
ledonger 0:d2c18f736df1 18 -1 : Checksum Error
ledonger 0:d2c18f736df1 19 */
ledonger 0:d2c18f736df1 20 int readData(void){
ledonger 0:d2c18f736df1 21 this->data = 0;
ledonger 0:d2c18f736df1 22 this->dataPin.output();
ledonger 0:d2c18f736df1 23 // Request a measurement (low during t > 18ms)
ledonger 0:d2c18f736df1 24 this->dataPin = 0;
ledonger 0:d2c18f736df1 25 wait_ms(20);
ledonger 0:d2c18f736df1 26 this->dataPin = 1;
ledonger 0:d2c18f736df1 27
ledonger 0:d2c18f736df1 28 //Wait for the sensor to take control and set low level /!\ Important
ledonger 0:d2c18f736df1 29 wait_us(20);
ledonger 0:d2c18f736df1 30
ledonger 0:d2c18f736df1 31 this->dataPin.input();
ledonger 0:d2c18f736df1 32
ledonger 0:d2c18f736df1 33 //TODO Check if timing is correct (low : 80µs ; high 80µs)
ledonger 0:d2c18f736df1 34 // Wait until end of 80µs low
ledonger 0:d2c18f736df1 35 while(!this->dataPin.read());
ledonger 0:d2c18f736df1 36 // Wait until end of 80 µs high
ledonger 0:d2c18f736df1 37 while(this->dataPin.read());
ledonger 0:d2c18f736df1 38
ledonger 0:d2c18f736df1 39 // Sensor reply 40bits
ledonger 0:d2c18f736df1 40 for(iBit=0; iBit<40; iBit++) {
ledonger 0:d2c18f736df1 41 this->data = this->data << 1; // Shift for new number
ledonger 0:d2c18f736df1 42 this->timer.stop();
ledonger 0:d2c18f736df1 43 this->timer.reset();
ledonger 0:d2c18f736df1 44
ledonger 0:d2c18f736df1 45 // Wait for low level to end
ledonger 0:d2c18f736df1 46 while(!this->dataPin.read());
ledonger 0:d2c18f736df1 47 this->timer.start();
ledonger 0:d2c18f736df1 48 // Count time while high level
ledonger 0:d2c18f736df1 49 while(this->dataPin.read());
ledonger 0:d2c18f736df1 50
ledonger 0:d2c18f736df1 51 if(this->timer.read_us() > 50)
ledonger 0:d2c18f736df1 52 {
ledonger 0:d2c18f736df1 53 //This bit is '1'
ledonger 0:d2c18f736df1 54 this->data++;
ledonger 0:d2c18f736df1 55 }
ledonger 0:d2c18f736df1 56 }
ledonger 0:d2c18f736df1 57
ledonger 0:d2c18f736df1 58 wait_ms(250);
ledonger 0:d2c18f736df1 59
ledonger 0:d2c18f736df1 60 //Checking checksum
ledonger 0:d2c18f736df1 61 if((this->data & 0x00000000000000ff) != ((this->data & 0x000000ff00000000) >> 32) +
ledonger 0:d2c18f736df1 62 ((this->data & 0x00000000ff000000) >> 24) +
ledonger 0:d2c18f736df1 63 ((this->data & 0x0000000000ff0000) >> 16) +
ledonger 0:d2c18f736df1 64 ((this->data & 0x000000000000ff00) >> 8))
ledonger 0:d2c18f736df1 65 {
ledonger 0:d2c18f736df1 66 return -1;
ledonger 0:d2c18f736df1 67 }
ledonger 0:d2c18f736df1 68
ledonger 0:d2c18f736df1 69 return 1;
ledonger 0:d2c18f736df1 70 }
ledonger 0:d2c18f736df1 71
ledonger 0:d2c18f736df1 72 int getTemperature(void){
ledonger 0:d2c18f736df1 73 return (int)((this->data & 0x0000000000ff0000) >> 16);
ledonger 0:d2c18f736df1 74 }
ledonger 0:d2c18f736df1 75
ledonger 0:d2c18f736df1 76 int getHumidity(void){
ledonger 0:d2c18f736df1 77 return (int)((this->data & 0x000000ff00000000) >> 32);
ledonger 0:d2c18f736df1 78 }
ledonger 0:d2c18f736df1 79
ledonger 0:d2c18f736df1 80
ledonger 0:d2c18f736df1 81 private:
ledonger 0:d2c18f736df1 82 DigitalInOut dataPin;//Communication with the sensor
ledonger 0:d2c18f736df1 83 Timer timer; //initialize timer
ledonger 0:d2c18f736df1 84 uint64_t data; // 64 bit variable for temporary data
ledonger 0:d2c18f736df1 85 int iBit;
ledonger 0:d2c18f736df1 86 };
ledonger 1:023e1eae2048 87
ledonger 1:023e1eae2048 88
ledonger 1:023e1eae2048 89 #endif