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Software/Cpp/grovepi_analog_write.cpp

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+// GrovePi Example for using the analog write
+// http://dexterindustries.com/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"
+using namespace GrovePi;
+
+// sudo g++ -Wall grovepi.cpp grovepi_analog_write.cpp -o grovepi_analog_write.out -> without grovepicpp package installed
+// sudo g++ -Wall -lgrovepicpp grovepi_analog_write.cpp -o grovepi_analog_write.out -> with grovepicpp package installed
+
+int main()
+{
+	int pin = 3; // we use port D3
+
+	// for direction = HIGH the value we write increases with each step
+	// for direction = LOW the value we write decreases with each step
+	int direction = HIGH;
+	int increment_value = 3; // step increase for PWN function
+	int final_value = 0; // variable to hold to value to write to GrovePi
+
+	try
+	{
+		initGrovePi(); // initialize communication w/ GrovePi
+		pinMode(pin, OUTPUT); // set the pin mode for writing
+
+		// continuously do this
+		while(true)
+		{
+			// iterate the whole range of values
+			// 0 -> 255 maps to 0V -> VCC, where VCC is the supply voltage on GrovePi
+			//
+			// since we're using the a PWM function
+			// we have a duty cycle that goes from 0% to 100% of VCC voltage
+			// with an increase/decrease of voltage of 100 * increment_value / 256 = 0.39%  / increment
+			//
+			// google what a PWM wave is
+			for(int value = 0; value <= 255; value += increment_value)
+			{
+				final_value = 0; // reset it
+				if(direction == HIGH)
+					// if direction == HIGH then let the final_value take ascending values
+					final_value = value;
+				else if(direction == LOW)
+					// if direction == LOW then let the final_value take descending values
+					final_value = 255 - value;
+
+				printf("[pin %d][analog write = %d]\n", pin, final_value);
+				analogWrite(pin, final_value);
+				delay(5); // wait 5 ms for the next change in pin value
+			}
+
+			// if increment_value = HIGH then change it to increment_value = LOW
+			// if increment_value = LOW then change it to increment_value = HIGH
+			direction = (direction == HIGH) ? LOW : HIGH;
+		}
+	}
+	catch (I2CError &error)
+	{
+		printf(error.detail());
+
+		return -1;
+	}
+
+	return 0;
+}