diff examples/03-Analog/analog-input/render.cpp @ 464:8fcfbfb32aa0 prerelease

Examples reorder with subdirectories. Added header to each project. Moved Doxygen to bottom of render.cpp.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/03-Analog/analog-input/render.cpp	Mon Jun 20 16:20:38 2016 +0100
@@ -0,0 +1,114 @@
+/*
+ ____  _____ _        _    
+| __ )| ____| |      / \   
+|  _ \|  _| | |     / _ \  
+| |_) | |___| |___ / ___ \ 
+|____/|_____|_____/_/   \_\
+
+The platform for ultra-low latency audio and sensor processing
+
+http://bela.io
+
+A project of the Augmented Instruments Laboratory within the
+Centre for Digital Music at Queen Mary University of London.
+http://www.eecs.qmul.ac.uk/~andrewm
+
+(c) 2016 Augmented Instruments Laboratory: Andrew McPherson,
+  Astrid Bin, Liam Donovan, Christian Heinrichs, Robert Jack,
+  Giulio Moro, Laurel Pardue, Victor Zappi. All rights reserved.
+
+The Bela software is distributed under the GNU Lesser General Public License
+(LGPL 3.0), available here: https://www.gnu.org/licenses/lgpl-3.0.txt
+*/
+
+
+#include <Bela.h>
+#include <rtdk.h>
+#include <cmath>
+
+float gPhase;
+float gInverseSampleRate;
+int gAudioFramesPerAnalogFrame;
+
+// These settings are carried over from main.cpp
+// Setting global variables is an alternative approach
+// to passing a structure to userData in setup()
+
+extern int gSensorInputFrequency;
+extern int gSensorInputAmplitude;
+
+bool setup(BelaContext *context, void *userData)
+{
+	if(context->analogFrames == 0 || context->analogFrames > context->audioFrames) {
+		rt_printf("Error: this example needs analog enabled, with 4 or 8 channels\n");
+		return false;
+	}
+
+	gAudioFramesPerAnalogFrame = context->audioFrames / context->analogFrames;
+	gInverseSampleRate = 1.0 / context->audioSampleRate;
+	gPhase = 0.0;
+
+	return true;
+}
+
+void render(BelaContext *context, void *userData)
+{
+	float frequency = 440.0;
+	float amplitude = 0.8;
+
+	// There are twice as many audio frames as matrix frames since audio sample rate
+	// is twice as high
+
+	for(unsigned int n = 0; n < context->audioFrames; n++) {
+		if(!(n % gAudioFramesPerAnalogFrame)) {
+			// Even audio samples: update frequency and amplitude from the matrix
+			frequency = map(analogRead(context, n/gAudioFramesPerAnalogFrame, gSensorInputFrequency), 0, 1, 100, 1000);
+			amplitude = analogRead(context, n/gAudioFramesPerAnalogFrame, gSensorInputAmplitude);
+		}
+
+		float out = amplitude * sinf(gPhase);
+
+		for(unsigned int channel = 0; channel < context->audioChannels; channel++)
+			context->audioOut[n * context->audioChannels + channel] = out;
+
+		gPhase += 2.0 * M_PI * frequency * gInverseSampleRate;
+		if(gPhase > 2.0 * M_PI)
+			gPhase -= 2.0 * M_PI;
+	}
+}
+
+void cleanup(BelaContext *context, void *userData)
+{
+
+}
+
+/* ------------ Project Explantation ------------ */
+
+/**
+\example 03-analog-input
+
+Connecting potentiometers
+-------------------------
+
+This sketch produces a sine tone, the frequency and amplitude of which are 
+affected by data received on the analog pins. Before looping through each audio 
+frame, we declare a value for the frequency and amplitude of our sine tone 
+(line 55); we adjust these values by taking in data from analog sensors 
+(for example potentiometers) with `analogRead()`.
+
+- connect a 10K pot to 3.3V and GND on its 1st and 3rd pins.
+- connect the 2nd middle pin of the pot to analogIn 0.
+- connect another 10K pot in the same way but with the middle pin connected to analogIn 1.
+
+The important thing to notice is that audio is sampled twice as often as analog 
+data. The audio sampling rate is 44.1kHz (44100 frames per second) and the 
+analog sampling rate is 22.05kHz (22050 frames per second). On line 62 you might 
+notice that we are processing the analog data and updating frequency and 
+amplitude only on every second audio sample, since the analog sampling rate is 
+half that of the audio.
+
+Note that the pin numbers are stored in the variables `gAnalogInputFrequency` and 
+`gAnalogInputAmplitude`. These are declared in the main.cpp file; if you look in 
+that file you will see that they have the values of 0 and 1. Bear in mind that 
+these are analog input pins which is a specific header!
+*/