+ 0.1.09

+ optimize size
+ timeout check
+ use of mask to minimize shifts
+ added time measurement in dht22_test
+ reindented code

libraries/DHTlib/dht.cpp

@@ -6,6 +6,7 @@
 //     URL: http://arduino.cc/playground/Main/DHTLib
 //
 // HISTORY:
+// 0.1.09 optimize size: timeout check + use of mask
 // 0.1.08 added formula for timeout based upon clockspeed
 // 0.1.07 added support for DHT21
 // 0.1.06 minimize footprint (2012-12-27)
@@ -26,6 +27,9 @@
 // #define TIMEOUT 10000
 // uint16_t for UNO, higher CPU speeds => exceed MAXINT.
 // works for DUE
+// 16 MHz => 10000
+// 84 MHz => 52500
+// 100MHz => 62500
 #define TIMEOUT (F_CPU/1600)
 
 
@@ -115,7 +119,7 @@ int dht::read22(uint8_t pin)
 int dht::read(uint8_t pin)
 {
     // INIT BUFFERVAR TO RECEIVE DATA
-	uint8_t cnt = 7;
+    uint8_t mask = 128;
     uint8_t idx = 0;
 
     // EMPTY BUFFER
@@ -129,36 +133,35 @@ int dht::read(uint8_t pin)
     delayMicroseconds(40);
     pinMode(pin, INPUT);
 
-    // TODO rewrite with miros()?
     // GET ACKNOWLEDGE or TIMEOUT
     unsigned int loopCnt = TIMEOUT;
     while(digitalRead(pin) == LOW)
-		if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+    if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
 
     loopCnt = TIMEOUT;
     while(digitalRead(pin) == HIGH)
-		if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+    if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
 
     // READ THE OUTPUT - 40 BITS => 5 BYTES
     for (uint8_t i=0; i<40; i++)
     {
         loopCnt = TIMEOUT;
         while(digitalRead(pin) == LOW)
-			if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+        if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
 
         unsigned long t = micros();
 
         loopCnt = TIMEOUT;
         while(digitalRead(pin) == HIGH)
-			if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+        if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
 
-		if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
-		if (cnt == 0)   // next byte?
+        if ((micros() - t) > 40) bits[idx] |= mask;
+        mask >>= 1;
+        if (mask == 0)   // next byte?
         {
-			cnt = 7;   
+            mask = 128;
             idx++;
         }
-		else cnt--;
     }
 
     return DHTLIB_OK;

libraries/DHTlib/dht.h

@@ -1,7 +1,7 @@
 //
 //    FILE: dht.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.08
+// VERSION: 0.1.09
 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
 //     URL: http://arduino.cc/playground/Main/DHTLib
 //
@@ -18,7 +18,7 @@
 #include <Arduino.h>
 #endif
 
-#define DHT_LIB_VERSION "0.1.08"
+#define DHT_LIB_VERSION "0.1.09"
 
 #define DHTLIB_OK				0
 #define DHTLIB_ERROR_CHECKSUM	-1

libraries/DHTlib/examples/dht22_test/dht22_test.ino

@@ -1,8 +1,7 @@
-
 //
 //    FILE: dht22_test.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.00
+// VERSION: 0.1.01
 // PURPOSE: DHT library test sketch for DHT22 && Arduino
 //     URL:
 //
@@ -22,14 +21,18 @@ void setup()
     Serial.print("LIBRARY VERSION: ");
     Serial.println(DHT_LIB_VERSION);
     Serial.println();
-  Serial.println("Type,\tstatus,\tHumidity (%),\tTemperature (C)");
+    Serial.println("Type,\tstatus,\tHumidity (%),\tTemperature (C)\tTime (us)");
 }
 
 void loop()
 {
     // READ DATA
     Serial.print("DHT22, \t");
+
+    uint32_t start = micros();
     int chk = DHT.read22(DHT22_PIN);
+    uint32_t stop = micros();
+
     switch (chk)
     {
     case DHTLIB_OK:
@@ -48,7 +51,10 @@ void loop()
     // DISPLAY DATA
     Serial.print(DHT.humidity, 1);
     Serial.print(",\t");
-  Serial.println(DHT.temperature, 1);
+    Serial.print(DHT.temperature, 1);
+    Serial.print(",\t");
+    Serial.print(stop - start);
+    Serial.println();
 
     delay(2000);
 }