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Software/Cpp/grove_dht_pro/grove_dht_example.cpp

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+//
+// GrovePi Example for using the Grove Temperature & Humidity Sensor Pro
+// (http://www.seeedstudio.com/wiki/Grove_-_Temperature_and_Humidity_Sensor_Pro)
+//
+// The GrovePi connects the Raspberry Pi and Grove sensors.
+// You can learn more about GrovePi here:  http://www.dexterindustries.com/GrovePi
+//
+// Have a question about this example?  Ask on the forums here:  http://forum.dexterindustries.com/c/grovepi
+//
+/*
+## License
+
+   The MIT License (MIT)
+
+   GrovePi for the Raspberry Pi: an open source platform for connecting Grove Sensors to the Raspberry Pi.
+   Copyright (C) 2017  Dexter Industries
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+*/
+
+#include "grovepi.h"
+#include "grove_dht_pro.h"
+
+using GrovePi::DHT;
+using GrovePi::delay;
+using GrovePi::I2CError;
+
+// sudo g++ -Wall grovepi.cpp grove_dht_pro.cpp grove_dht_example.cpp -o grove_dht_example.out -> without grovepicpp package installed
+// sudo g++ -Wall -lgrovepicpp grove_dht_pro.cpp grove_dht_example.cpp -o grove_dht_example.out -> with grovepicpp package installed
+
+int main()
+{
+	int sensorPin = 4; // digital port (D4) to which we have DTH serial sensor connected
+	float temp = 0, humidity = 0; // variables to hold data from the DHT sensor
+
+	// initialize the BLUE module (got from the GrovePi kit)
+	// and use digital port 4 for the DHT sensor
+	DHT dht = DHT(DHT::BLUE_MODULE, sensorPin);
+
+	try
+	{
+		dht.init(); // same as initGrovePi
+
+		// do this indefinitely
+		while(true)
+		{
+			// read the DHT sensor values
+			dht.getSafeData(temp, humidity);
+
+			// and print them on the screen
+			printf("[temp = %.02f C][humidity = %.02f%%]\n", temp, humidity);
+
+			// and wait 100 before the other reading
+			// so we don't overflow the terminal
+			delay(100);
+		}
+	}
+	catch(I2CError &error)
+	{
+		// I2C error while reading / writing
+		printf(error.detail());
+		return -1;
+	}
+	catch(std::runtime_error &e)
+	{
+		// catch error on number values
+		// NaN & bad value readings
+		printf(e.what());
+		return -2;
+	}
+
+	return 0;
+}

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);
+}

Software/Cpp/grove_dht_pro/grove_dht_pro.h

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+#ifndef GROVE_RGB_LCD_H
+#define GROVE_RGB_LCD_H
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <linux/i2c-dev.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdint.h>
+#include <stdexcept>
+#include <cmath>
+
+#include "grovepi.h"
+
+namespace GrovePi
+{
+  class DHT
+  {
+	  public:
+
+		  const static uint8_t BLUE_MODULE = 0;
+		  const static uint8_t WHITE_MODULE = 1;
+
+		  DHT(const uint8_t _module_type = BLUE_MODULE, const uint8_t _pin = 4)
+			  : module_type(_module_type), pin(_pin) {
+		  }
+
+		  void init();
+		  void getSafeData(float &temp, float &humidity);
+		  void getUnsafeData(float &temp, float &humidity);
+
+	  private:
+
+		  uint8_t DEVICE_FILE; // I2C device file
+		  const uint8_t module_type;
+		  const uint8_t pin;
+		  const static uint8_t DHT_TEMP_CMD = 40; // command for reaching DTH sensor on the GrovePi
+		  const static int MAX_RETRIES = 3;
+
+		  // converts the first 4 bytes of the array
+		  // into a float
+		  static const float fourBytesToFloat(uint8_t *data);
+		  static const bool areGoodReadings(int temp, int humidity);
+
+  };
+}
+
+
+#endif