Fiddling with the old fibomod algorithm

Fibomod/Fibomod.ino

@@ -0,0 +1,88 @@
+// can fibomod make an interesting noise?
+
+
+#include <Adafruit_MCP4728.h>
+#include <Wire.h>
+
+Adafruit_MCP4728 mcp;
+
+#define nsamp 256
+#define dacmax 256
+
+unsigned int phase = 0;
+unsigned int fibo = 20;
+unsigned int scale = 0;
+
+byte waveform[nsamp];
+
+void setup() {
+
+  cli();
+
+//set timer1 interrupt at 1Hz
+  TCCR1A = 0;// set entire TCCR1A register to 0
+  TCCR1B = 0;// same for TCCR1B
+  TCNT1  = 0;//initialize counter value to 0
+  // set compare match register for 1hz increments
+  //OCR1A = 15624;// = (16*10^6) / (1*1024) - 1 (must be <65536)
+  //OCR1A = 7812;// = (16*10^6) / (1*1024) - 1 (must be <65536)
+  OCR1A = 10000;
+  // turn on CTC mode
+  TCCR1B |= (1 << WGM12);
+  // Set CS10 and CS12 bits for 1024 prescaler
+  TCCR1B |= (1 << CS12) | (1 << CS10);  
+  // enable timer compare interrupt
+  TIMSK1 |= (1 << OCIE1A);
+
+  sei();
+
+
+  Serial.begin(115200);
+
+  if (!mcp.begin(0x64)) {
+    while (1) {
+      delay(100);
+    }
+  }
+
+  mcp.setSpeed(800000L);
+
+  for( int i = 0; i < nsamp; i++ ) {
+    waveform[i] = 1;
+  }
+
+}
+
+ISR(TIMER1_COMPA_vect){//timer1
+  unsigned int flog;
+  scale = 10;
+  fibo = 3 + analogRead(A0) >> 2;
+  flog = fibo;
+  while( flog ) {
+    flog = flog >> 1;
+    scale -= 1;
+  }
+  Serial.println(fibo);
+  Serial.println(scale);
+  Serial.println(fibo << scale);
+}
+
+
+
+void loop() {
+  int p0 = phase - 1;
+  int p1 = phase + 2;
+  if( p0 < 0 ) {
+    p0 += nsamp;
+  }
+  if( p1 < 0 ) {
+    p1 += nsamp;
+  }
+  waveform[phase] = (waveform[p1] + waveform[p0]) % fibo;
+  mcp.fastWrite(waveform[phase] << scale, 0, 0, 0);
+  phase += 1;
+  if( phase >= nsamp ) {
+    phase = 0;
+  }
+}
+