first commit

Software/Cpp/grove_dht_pro/grove_dht_pro.cpp

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+#include "grove_dht_pro.h"
+
+using std::runtime_error;
+using GrovePi::DHT;
+
+/**
+ * function for connecting to the GrovePi
+ * doesn't matter whether you call it multiple times
+ * just check with the isConnected() function to see if you got a connection
+ */
+void DHT::init()
+{
+	initGrovePi();
+}
+
+/**
+ * returns via its parameters the temperature and humidity
+ * this function is NaN-proof
+ * it always gives "accepted" values
+ *
+ * if bad values are read, then it will retry reading them
+ * and check if they are okay for a number of [MAX_RETRIES] times
+ * before throwing a [runtime_error] exception
+ *
+ * @param temp     in Celsius degrees
+ * @param humidity in percentage values
+ */
+void DHT::getSafeData(float &temp, float &humidity)
+{
+	int current_retry  = 0;
+	this->getUnsafeData(temp, humidity); // read data from GrovePi once
+
+	// while values got are not okay / accepteed
+	while((std::isnan(temp) || std::isnan(humidity) || !this->areGoodReadings(temp, humidity))
+	      && current_retry < this->MAX_RETRIES)
+	{
+		// reread them again
+		current_retry += 1;
+		this->getUnsafeData(temp, humidity);
+	}
+
+	// if even after [MAX_RETRIES] attempts at getting good values
+	// nothing good came, then throw one of the bottom exceptions
+
+	if(std::isnan(temp) || std::isnan(humidity))
+		throw runtime_error("[GroveDHT NaN readings - check analog port]\n");
+
+	if(!DHT::areGoodReadings(temp, humidity))
+		throw runtime_error("[GroveDHT bad readings - check analog port]\n");
+}
+
+/**
+ * function for returning via its arguments the temperature & humidity
+ * it's not recommended to use this function since it might throw
+ * some NaN or out-of-interval values
+ *
+ * use it if you come with your own implementation
+ * or if you need it for some debugging
+ *
+ * @param temp     in Celsius degrees
+ * @param humidity in percentage values
+ */
+void DHT::getUnsafeData(float &temp, float &humidity)
+{
+	writeBlock(this->DHT_TEMP_CMD, this->pin, this->module_type);
+	readByte();
+
+	uint8_t data_block[33];
+	readBlock(data_block);
+
+	temp = DHT::fourBytesToFloat(data_block + 1);
+	humidity = DHT::fourBytesToFloat(data_block + 5);
+}
+
+/**
+ * function for converting 4 unsigned bytes of data
+ * into a single float
+ * @param  byte_data array to hold the 4 data sets
+ * @return           the float converted data
+ */
+const float DHT::fourBytesToFloat(uint8_t *byte_data)
+{
+	float output;
+
+	// reinterpret_cast guarantees that if you cast a pointer
+	// to a different type, and then reinterpret_cast it back
+	// to the original type, you get the original value.
+	//
+	// as opposed to the static_cast where it only guarantees
+	// the address is preserved
+	//
+	// so we take the 1st address &byte_data[0],
+	// the 5th address &byte_data[4] (the end address)
+	// and translate the output into a unsigned byte type
+	std::copy(reinterpret_cast<const uint8_t*>(&byte_data[0]),
+	          reinterpret_cast<const uint8_t*>(&byte_data[4]),
+	          reinterpret_cast<uint8_t*>(&output));
+
+	return output;
+}
+
+const bool DHT::areGoodReadings(int temp, int humidity)
+{
+	return (temp > -100.0 && temp < 150.0 && humidity >= 0.0 && humidity <= 100.0);
+}