Revision 0:d0c08e2c4315, committed 2020-01-08

Comitter:

quickeman

Date:

Wed Jan 08 19:17:43 2020 +0000

Commit message:

Basic recursive oscillator to be used with an Mbed and custom-designed control board.

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Jan 08 19:17:43 2020 +0000
@@ -0,0 +1,104 @@
+#include "mbed.h"
+#include "math.h"
+
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
+AnalogIn pitchIn(p20);
+AnalogIn levelIn(p19);
+AnalogOut output(p18);
+DigitalIn switchIn(p21);
+DigitalOut led(LED1);
+
+Ticker takePitch;
+Ticker takeLevel;
+Ticker outputSig;
+
+float pitch;
+float level;
+float freqNorm;
+
+// Recursive oscillator variables
+float y;
+float y_n1;
+float y_n2;
+float outSig;
+
+void initOsc() {
+    // Initialise values of recursive oscillator variables
+    y = 0;
+    y_n1 = sin(2 * M_PI * (1 - freqNorm));
+    y_n2 = sin(2 * M_PI * (1 - (2 * freqNorm)));
+}
+
+// Flag variables
+bool flag1 = 0;
+bool flag2 = 0;
+
+void getPitch() {
+    // Read in relative pitch value
+    pitch = pitchIn.read();
+    flag2 = 1;
+}
+
+float getNormFreq(float freq, float max, float sampRate) {
+    // Returns the normalised frequency for given input
+    // freq: input frequency/pitch 0-1
+    // max: maximum pitch defined in Hz
+    // sampRate: sample rate in Hz
+    float normFreq = freq * (max / sampRate);
+    return normFreq;
+}
+
+void getLevel() {
+    // Read in desired output level
+    level = levelIn.read();
+}
+
+void genNext() {
+    // Recursive oscillator
+    y = (2 * cos(2 * M_PI * freqNorm) * y_n1) - y_n2;
+    y_n2 = y_n1;
+    y_n1 = y;
+}
+
+void outputSignal() {
+    // Output signal
+    output.write(outSig);
+    flag1 = 1;
+}
+
+int main() {
+    float sampFreq = 48000.0; // Hz
+    float sampTime = 1.0 / sampFreq; // s
+    float pitchMax = 9600.0; // Hz
+    
+    getPitch();
+    freqNorm = getNormFreq(pitch, pitchMax, sampFreq);
+    flag2 = 0;
+    getLevel();
+    
+    initOsc();
+
+    takePitch.attach(&getPitch, 0.1);
+    takeLevel.attach(&getLevel, 0.1);
+    outputSig.attach(&outputSignal, sampTime);
+    
+    while(1) {
+        if(flag1) {
+            genNext();
+            if (switchIn.read()) {
+                outSig = (level * y) / 33.0;
+            } else {
+                outSig = level * y;
+            }
+            flag1 = 0;
+        }
+        if(flag2){
+            freqNorm = getNormFreq(pitch, pitchMax, sampFreq);
+            flag2 = 0;
+        }
+        led = switchIn;
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Wed Jan 08 19:17:43 2020 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/users/mbed_official/code/mbed/builds/65be27845400
\ No newline at end of file