Diff: DHT11.h

Revision:

0:d2c18f736df1

Child:

1:023e1eae2048

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DHT11.h	Fri Apr 07 11:36:47 2017 +0000
@@ -0,0 +1,85 @@
+#include "mbed.h"
+
+//Class to manage DHT11 sensor
+class DHT11{
+  
+    public:
+        /* Takes the data pin of the sensor in parameter */
+        DHT11(PinName pin):dataPin(pin)
+        {
+            iBit = 0;
+            data = 0;
+        }  
+        
+        /*  Request and receive new data from sensor
+            Returns : 
+                1 : OK
+                -1 : Checksum Error
+        */
+        int readData(void){
+            this->data = 0;
+            this->dataPin.output(); 
+            // Request a measurement (low during t > 18ms)
+            this->dataPin = 0;
+            wait_ms(20);
+            this->dataPin = 1;
+            
+            //Wait for the sensor to take control and set low level /!\ Important
+            wait_us(20);
+            
+            this->dataPin.input();
+            
+        //TODO Check if timing is correct (low : 80µs ; high 80µs)
+            // Wait until end of 80µs low
+            while(!this->dataPin.read());
+            // Wait until end of 80 µs high
+            while(this->dataPin.read());
+            
+            // Sensor reply 40bits 
+            for(iBit=0; iBit<40; iBit++) {
+                this->data = this->data << 1; // Shift for new number
+                this->timer.stop(); 
+                this->timer.reset(); 
+                
+                // Wait for low level to end
+                while(!this->dataPin.read());       
+                this->timer.start();     
+                // Count time while high level     
+                while(this->dataPin.read());
+                
+                if(this->timer.read_us() > 50) 
+                {
+                    //This bit is '1'
+                    this->data++;
+                }
+            }
+            
+            wait_ms(250);
+            
+            //Checking checksum
+            if((this->data & 0x00000000000000ff) != ((this->data & 0x000000ff00000000) >> 32) + 
+                                                    ((this->data & 0x00000000ff000000) >> 24) + 
+                                                    ((this->data & 0x0000000000ff0000) >> 16) + 
+                                                    ((this->data & 0x000000000000ff00) >> 8))
+            {
+                return -1;        
+            }
+            
+            return 1;
+        }
+        
+        int getTemperature(void){
+            return (int)((this->data & 0x0000000000ff0000) >> 16);
+        }
+        
+        int getHumidity(void){
+            return (int)((this->data & 0x000000ff00000000) >> 32);
+        }
+        
+    
+    private:
+        DigitalInOut dataPin;//Communication with the sensor
+        Timer timer; //initialize timer
+        uint64_t data; // 64 bit variable for temporary data
+        int iBit;
+};