Merge pull request #2 from ringerc/master

Arduino 1.0 update, access to integer values, inlines

DHT22.cpp

@@ -20,6 +20,10 @@
 Humidity and Temperature Sensor DHT22 info found at
 http://www.sparkfun.com/products/10167
 
+Version 0.5: 15 Jan 2012 by Craig Ringer
+- Updated to build against Arduino 1.0
+- Made accessors inline in the header so they can be optimized away
+
 Version 0.4: 24-Jan-2011 by Ben Adams
 Added return code constants to keywords.txt
 Returns DHT_ERROR_CHECKSUM on check sum mismatch 
@@ -41,10 +45,10 @@ The Arduino OneWire lib
 */
 
 #include "DHT22.h"
-#include "pins_arduino.h"
+#include <Arduino.h>
+#include <pins_arduino.h>
 
 extern "C" {
-#include "WConstants.h"
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include <avr/pgmspace.h>
@@ -61,7 +65,7 @@ extern "C" {
 
 DHT22::DHT22(uint8_t pin)
 {
-    _bitmask =  digitalPinToBitMask(pin);
+    _bitmask = digitalPinToBitMask(pin);
     _baseReg = portInputRegister(digitalPinToPort(pin));
     _lastReadTime = millis();
     _lastHumidity = DHT22_ERROR_VALUE;
@@ -201,16 +205,16 @@ DHT22_ERROR_t DHT22::readData()
     }
   }
 
-  _lastHumidity = (float(currentHumidity & 0x7FFF) / 10.0);
+  _lastHumidity = currentHumidity & 0x7FFF;
   if(currentTemperature & 0x8000)
   {
-   // Below zero, non standard way of encoding negative numbers!
-    currentTemperature &= 0x7FFF;
-    _lastTemperature = (float(currentTemperature) / 10.0) * -1.0;
+    // Below zero, non standard way of encoding negative numbers!
+    // Convert to native negative format.
+    _lastTemperature = -currentTemperature & 0x7FFF;
   }
   else
   {
-    _lastTemperature = float(currentTemperature) / 10.0;
+    _lastTemperature = currentTemperature;
   }
 
   csPart1 = currentHumidity >> 8;
@@ -224,16 +228,6 @@ DHT22_ERROR_t DHT22::readData()
   return DHT_ERROR_CHECKSUM;
 }
 
-float DHT22::getHumidity()
-{
-  return _lastHumidity;
-}
-
-float DHT22::getTemperatureC()
-{
-  return _lastTemperature;
-}
-
 //
 // This is used when the millis clock rolls over to zero
 //

DHT22.h

@@ -3,7 +3,7 @@
 
 #include <inttypes.h>
 
-#define DHT22_ERROR_VALUE -99.5
+#define DHT22_ERROR_VALUE -995
 
 typedef enum
 {
@@ -23,15 +23,54 @@ class DHT22
     uint8_t _bitmask;
     volatile uint8_t *_baseReg;
     unsigned long _lastReadTime;
-    float _lastHumidity;
-    float _lastTemperature;
+    short int _lastHumidity;
+    short int _lastTemperature;
 
   public:
     DHT22(uint8_t pin);
-    DHT22_ERROR_t readData(void);
+    DHT22_ERROR_t readData();
+	short int getHumidityInt();
+	short int getTemperatureCInt();
+    void clockReset();
+#if !defined(DHT22_NO_FLOAT)
     float getHumidity();
     float getTemperatureC();
-    void clockReset();
+#endif
 };
 
+// Report the humidity in .1 percent increments, such that 635 means 63.5% relative humidity
+//
+// Converts from the internal integer format on demand, so you might want
+// to cache the result.
+inline short int DHT22::getHumidityInt()
+{
+  return _lastHumidity;
+}
+
+// Get the temperature in decidegrees C, such that 326 means 32.6 degrees C.
+// The temperature may be negative, so be careful when handling the fractional part.
+inline short int DHT22::getTemperatureCInt()
+{
+  return _lastTemperature;
+}
+
+#if !defined(DHT22_NO_FLOAT)
+// Return the percentage relative humidity in decimal form
+inline float DHT22::getHumidity()
+{
+  return float(_lastHumidity)/10;
+}
+#endif
+
+#if !defined(DHT22_NO_FLOAT)
+// Return the percentage relative humidity in decimal form
+//
+// Converts from the internal integer format on demand, so you might want
+// to cache the result.
+inline float DHT22::getTemperatureC()
+{
+  return float(_lastTemperature)/10;
+}
+#endif //DHT22_SUPPORT_FLOAT
+
 #endif /*_DHT22_H_*/

README

@@ -2,7 +2,20 @@
   Developed by Ben Adams - 2011
 
 Humidity and Temperature Sensor DHT22 info found at
-http://www.sparkfun.com/products/10167
+  http://www.sparkfun.com/products/10167
+The same sensor has also been spotted going by the names RHT22, AM2302
+and RHT03 from a variety of vendors. It uses a non-standard 1-wire digital
+signalling protocol.
+
+To install this library for use with the Arduino IDE, copy it
+to the `libraries' folder and restart the IDE. For an example of
+how to use it, see File->Examples->DHT22->Serial .
+
+Version 0.5: 15-Jan-2012 by Craig Ringer
+Update to support Arduino 1.0
+Make accessors inlineable so they can be optimised away
+Preserve original integer values from sensor and offer access to them
+Permit floating point support to be disalbed by defining DHT22_NO_FLOAT before including DHT22.h
 
 Version 0.4: 24-Jan-2011 by Ben Adams
 Added return code constants to keywords.txt

examples/Serial/Serial.pde → examples/Serial/Serial.ino

@@ -1,4 +1,6 @@
 #include <DHT22.h>
+// Only used for sprintf
+#include <stdio.h>
 
 // Data wire is plugged into port 7 on the Arduino
 // Connect a 4.7K resistor between VCC and the data pin (strong pullup)
@@ -17,8 +19,11 @@ void setup(void)
 void loop(void)
 { 
   DHT22_ERROR_t errorCode;
-
+
+  // The sensor can only be read from every 1-2s, and requires a minimum
+  // 2s warm-up after power-on.
   delay(2000);
+
   Serial.print("Requesting data...");
   errorCode = myDHT22.readData();
   switch(errorCode)
@@ -29,6 +34,14 @@ void loop(void)
       Serial.print("C ");
       Serial.print(myDHT22.getHumidity());
       Serial.println("%");
+      // Alternately, with integer formatting which is clumsier but more compact to store and
+	  // can be compared reliably for equality:
+	  //	  
+      char buf[128];
+      sprintf(buf, "Integer-only reading: Temperature %hi.%01hi C, Humidity %i.%01i %% RH",
+                   myDHT22.getTemperatureCInt()/10, abs(myDHT22.getTemperatureCInt()%10),
+                   myDHT22.getHumidityInt()/10, myDHT22.getHumidityInt()%10);
+      Serial.println(buf);
       break;
     case DHT_ERROR_CHECKSUM:
       Serial.print("check sum error ");
@@ -56,4 +69,4 @@ void loop(void)
       Serial.println("Polled to quick ");
       break;
   }
-}
+}

keywords.txt

@@ -14,7 +14,9 @@ DHT22	KEYWORD1
 
 readData	KEYWORD2
 getHumidity	KEYWORD2
+getHumidityInt	KEYWORD2
 getTemperatureC	KEYWORD2
+getTemperatureCInt KEYWORD2
 clockReset	KEYWORD2
 
 #######################################