diff projects/d-box/FeedbackOscillator.cpp @ 0:8a575ba3ab52

Initial commit.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/projects/d-box/FeedbackOscillator.cpp	Fri Oct 31 19:10:17 2014 +0100
@@ -0,0 +1,112 @@
+/*
+ * FeedbackOscillator.cpp
+ *
+ * Recursive phase-shift oscillator implemented
+ * on the matrix
+ *
+ * Andrew McPherson 2014
+ */
+
+#include "FeedbackOscillator.h"
+#include <cstdlib>
+#include <cmath>
+
+#define COEFF_B0 	0
+#define COEFF_B1	1
+#define COEFF_A1	2
+
+FeedbackOscillator::FeedbackOscillator()
+: wavetable1(0), wavetable2(0)
+{
+
+}
+
+FeedbackOscillator::~FeedbackOscillator() {
+	if(wavetable1 != 0)
+		free(wavetable1);
+	if(wavetable2 != 0)
+		free(wavetable2);
+
+}
+
+// Initialise the settings for the feedback oscillator
+void FeedbackOscillator::initialise(int maxTableSize, float hpfCutoffFrequency, float matrixSampleRate) {
+	wavetableMaxLength = maxTableSize;
+	if(wavetable1 != 0)
+		free(wavetable1);
+	if(wavetable2 != 0)
+		free(wavetable2);
+
+	wavetable1 = (float *)malloc(maxTableSize * sizeof(float));
+	wavetable2 = (float *)malloc(maxTableSize * sizeof(float));
+
+	float omega = tan(M_PI * hpfCutoffFrequency / matrixSampleRate);
+	float n = 1.0f / (1.0f + omega);
+
+	coeffs[COEFF_A1] = (omega - 1.0f) * n;
+	coeffs[COEFF_B0] = n;
+	coeffs[COEFF_B1] = -n;
+
+	for(int n = 0; n < maxTableSize; n++)
+		wavetable1[n] = wavetable2[n] = 0;
+
+	wavetableRead = wavetable1;
+	wavetableWrite = wavetable2;
+	wavetableWritePointer = 0;
+	sampleCount = lastTriggerCount = 0;
+}
+
+// Process one sample and store the output value
+// Returns true if the wavetable needs rendering
+int FeedbackOscillator::process(uint16_t input, uint16_t *output) {
+	float inFloat = input / 65536.0;
+	float outFloat = coeffs[COEFF_B0] * inFloat + coeffs[COEFF_B1] * lastInput - coeffs[COEFF_A1] * lastOutput;
+	int requestRenderLength = 0;
+
+	//outFloat *= 2.0;
+
+	int intOut = outFloat * 65536.0 + 32768;
+	if(intOut > 65535)
+		intOut = 65535;
+	if(intOut < 0)
+		intOut = 0;
+	//intOut = (intOut & 0xFF) << 8;
+	//if(intOut > 65535)
+	//	intOut = 65535;
+
+	*output = (uint16_t)intOut;
+
+	if(canTrigger && outFloat > 0 && lastOutput <= 0) {
+		triggered = true;
+		requestRenderLength = wavetableWritePointer;	// How many samples stored thus far?
+		if(requestRenderLength < 4)
+			requestRenderLength = 0;	// Ignore anything with fewer than 4 points
+
+		lastTriggerCount = sampleCount;
+		canTrigger = false;
+		wavetableWritePointer = 0;
+
+		// Swap buffers
+		float *temp = wavetableWrite;
+		wavetableWrite = wavetableRead;
+		wavetableRead = temp;
+	}
+
+	if(triggered) {
+		wavetableWrite[wavetableWritePointer] = outFloat;
+		if(++wavetableWritePointer >= wavetableMaxLength) {
+			triggered = false;
+			wavetableWritePointer = 0;
+		}
+	}
+
+	if(sampleCount - lastTriggerCount > 40)
+		canTrigger = true;
+
+	sampleCount++;
+
+	lastOutput = outFloat;
+	lastInput = inFloat;
+
+	return requestRenderLength;
+}