Initial structure for HalMultiSensor

Former-commit-id: 22bc809d9e6de8a2994f1df699ae74bb7245378f

arduino/HalMultiSensor/HardwareDHT11.cpp

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+//
+//    FILE: dht11.cpp
+// VERSION: 0.3.2
+// PURPOSE: DHT11 Temperature & Humidity Sensor library for Arduino
+// LICENSE: GPL v3 (http://www.gnu.org/licenses/gpl.html)
+//
+// DATASHEET: http://www.micro4you.com/files/sensor/DHT11.pdf
+//
+// HISTORY:
+// George Hadjikyriacou - Original version (??)
+// Mod by SimKard - Version 0.2 (24/11/2010)
+// Mod by Rob Tillaart - Version 0.3 (28/03/2011)
+// + added comments
+// + removed all non DHT11 specific code
+// + added references
+//
+
+#include "dht11.h"
+
+// returnvalues:
+//  0 : OK
+// -1 : checksum error
+// -2 : timeout
+int dht11::read(int pin)
+{
+	// BUFFER TO RECEIVE
+	uint8_t bits[5];
+	uint8_t cnt = 7;
+	uint8_t idx = 0;
+
+	// EMPTY BUFFER
+	for (int i=0; i< 5; i++) bits[i] = 0;
+
+	// REQUEST SAMPLE
+	pinMode(pin, OUTPUT);
+	digitalWrite(pin, LOW);
+	delay(18);
+	digitalWrite(pin, HIGH);
+	delayMicroseconds(40);
+	pinMode(pin, INPUT);
+
+	// ACKNOWLEDGE or TIMEOUT
+	unsigned int loopCnt = 10000;
+	while(digitalRead(pin) == LOW)
+		if (loopCnt-- == 0) return -2;
+
+	loopCnt = 10000;
+	while(digitalRead(pin) == HIGH)
+		if (loopCnt-- == 0) return -2;
+
+	// READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
+	for (int i=0; i<40; i++)
+	{
+		loopCnt = 10000;
+		while(digitalRead(pin) == LOW)
+			if (loopCnt-- == 0) return -2;
+
+		unsigned long t = micros();
+
+		loopCnt = 10000;
+		while(digitalRead(pin) == HIGH)
+			if (loopCnt-- == 0) return -2;
+
+		if ((micros() - t) > 40) bits[idx] |= (1 << cnt);
+		if (cnt == 0)   // next byte?
+		{
+			cnt = 7;    // restart at MSB
+			idx++;      // next byte!
+		}
+		else cnt--;
+	}
+
+	// WRITE TO RIGHT VARS
+        // as bits[1] and bits[3] are allways zero they are omitted in formulas.
+	humidity    = bits[0]; 
+	temperature = bits[2]; 
+
+	uint8_t sum = bits[0] + bits[2];  
+
+	if (bits[4] != sum) return -1;
+	return 0;
+}
+//
+// END OF FILE
+//