Two more experiments

BeepBox/BeepBox.ino

@@ -0,0 +1,116 @@
+//waveform generator
+
+// hacked from https://www.instructables.com/Arduino-Waveform-Generator-1/
+
+#include <Adafruit_MCP4728.h>
+#include <Wire.h>
+
+Adafruit_MCP4728 mcp;
+
+#define nsamp 32
+#define dacmax 256
+
+const byte nclk = 200; // a guess
+long int freq; //frequency in Hz
+long unsigned int phase;
+long unsigned int phase_inc;
+
+int note = 0;
+int gate;
+int decay = 2;
+
+float pattern[4];
+
+long unsigned int pattern_inc[4];
+
+void setup() {
+  TIMSK0 &= ~_BV(TOIE0); // disable timer0 overflow interrupt
+
+  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 = 3905;// = (16*10^6) / (1*1024) - 1 (must be <65536)
+  // 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(400000L);
+//  mcp.setSpeed(800000L);
+  mcp.setSpeed(800000L);
+
+  freq=440;
+  phase=0;
+  pattern[0] = 110.0;
+  pattern[1] = 82.40688922821751;
+  pattern[2] = 97.99885899543737;
+  pattern[3] = 82.40688922821751;
+
+  for( int i = 0; i < 4; i++ ) {
+    pattern_inc[i] = pattern[i] * 975592.231884058;
+  }
+
+  setwave();
+}
+
+const float pi=3.14159265;
+byte waveform[nsamp];
+byte phaseb = 0;
+void setwave(){
+  for (int isamp=0; isamp<nsamp; ++isamp){
+    float phip=(isamp+0.5)/nsamp;
+    float phi=2*pi*phip;
+    int val=0;
+
+    //saw
+    val = dacmax * isamp / nsamp;
+    //val = ( isamp < nsamp / 2 ) ? 0 : dacmax - 1;
+        //sine
+    //val=(sin(phi)+1.0)*dacmax/2;
+    //val=((sin(phi)+0.333*sin(3*phi))/0.943+1)*dacmax/2;
+
+    val=max(val,0);
+    val=min(val,dacmax-1);
+    waveform[isamp]=val;
+  }
+}
+
+
+
+ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz 
+  note += 1;
+  if( note > 3 ) {
+    note = 0;
+  }
+  phase_inc = pattern_inc[note];
+  gate = 4095;
+}
+ 
+
+
+void loop() {
+  phase += phase_inc;
+  int redphase = phase >> 27;
+  mcp.fastWrite(waveform[redphase] << 4, gate, 0, 0);
+  if( gate > 0 ) {
+    gate -= decay;
+  }
+}
+

Noisemakers/Noisemakers.ino

@@ -0,0 +1,81 @@
+// Very basic Karplus-Strong 
+
+// based on this explanation http://sites.music.columbia.edu/cmc/MusicAndComputers/chapter4/04_09.php
+
+
+#include <Adafruit_MCP4728.h>
+#include <Wire.h>
+
+Adafruit_MCP4728 mcp;
+
+#define nsamp 128
+#define dacmax 256
+
+unsigned int phase;
+unsigned int repeats;
+
+
+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 = 1952;
+  // 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(400000L);
+//  mcp.setSpeed(800000L);
+  mcp.setSpeed(800000L);
+
+  randomSeed(analogRead(A0));
+
+  phase=0;
+}
+
+byte waveform[nsamp];
+void pluck(){
+  for (int i=0; i<nsamp; ++i){
+    waveform[i]=random(256);
+  }
+}
+
+void loop() {
+  byte s1, s2;
+  int p0 = phase;
+  s1 = waveform[phase];
+  phase += 1;
+  if( phase > nsamp ) {
+    phase = 0;
+  }
+  s2 = waveform[phase];
+  waveform[p0] = ( s1 & s2 ) + ((s1 ^ s2) >> 1);
+  mcp.fastWrite(s1 << 4, 0, 0, 0);
+}
+
+ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz 
+    pluck();
+}
+