Added 26

26Slew/26Slew.ino

@@ -0,0 +1,170 @@
+// Better sequencer which uses interrupts
+
+#include <Adafruit_MCP4728.h>
+#include <Wire.h>
+
+Adafruit_MCP4728 mcp;
+
+
+float tuning[37];
+float voltrange = 4.85;  // measured this, probably not accurate
+float octave = 4096.0 / voltrange; // number of DAC steps in an octave
+
+
+// melody
+
+// int pitch[] = { 4, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+// -1, -1, -1, -1, -1, -1, -1, -1,-1, -1, -1, -1,2, -1, -1, -1, };
+// int dur[] = { 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+//             0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0,  };
+
+// hi hat
+
+int pitch[] = { 1, 3, 4, 10, 6, 3, 11, -1 };
+float dur[] = { 1,0.5,0.5,0.5,0.5,0.5,0.5,0.5,0.5, };
+
+
+int note = 0;
+int phrase = 8;
+
+int s;
+int bpm = 120;
+float beat_s = 60.0 / (float)bpm;
+float beat_m = 1000.0 * beat_s; 
+bool noteon = false;
+int beat = false;
+long notestart, notedur, barstart;
+int target, slew;
+float slewk = 0.005;
+
+void setup() {
+  Serial.begin(115200);
+
+  float freq = (float)bpm / 60.0;
+
+  int ocr = round(16000000.0 / (1024.0 * freq )) - 1;
+  Serial.println(ocr);
+  if( ocr < 65536 ) {
+
+    cli();
+
+    TCCR1A = 0;// set entire TCCR1A register to 0
+    TCCR1B = 0;// same for TCCR1B
+    TCNT1  = 0;//initialize counter value to 0
+    OCR1A = ocr; //ocr; 
+    // turn on CTC mode
+    TCCR1B |= (1 << WGM12);
+    // Set CS10 and CS12 bits for 1024 escaler
+    TCCR1B |= (1 << CS12) | (1 << CS10);  
+    // enable timer compare interrupt
+    TIMSK1 |= (1 << OCIE1A);
+
+    sei();
+
+  } else {
+    Serial.println("BPM out of range");
+  }
+
+  if (!mcp.begin(0x64)) {
+    while (1) {
+      delay(100);
+    }
+  }
+
+  // randomSeed(analogRead(A0));
+  mcp.setSpeed(800000L);
+  make_tuning(12);
+  note=0;
+  slew=0;
+  barstart=millis();
+}
+
+void make_tuning(int edo) {
+  float n0 = 0;
+  float edof = (float)edo;
+  for( int i = 0; i < 37; i++ ) {
+      tuning[i] = round(n0 + octave * (float)i / edof);
+  }
+
+}
+
+
+// mod_note argument is milliseconds from the start of last note
+float mod_note(int x) {
+  float xb = x / (0.2 * beat_m);
+  return 0.5 + 0.5 * xb * (xb - 1) * ( xb - 2);
+}
+
+// mod_note argument is milliseconds from the start of this bar
+float mod_bar(int x) {
+  return 0.5 + 0.5 * sin((float)x / (beat_m * 2));
+}
+
+void set_mod(MCP4728_channel_t channel, float v) {
+  int o;
+  o = round(v * 4095.0);
+  if( o > 4095 ) {
+    o = 4095;
+  }
+  if( o < 0 ) {
+    o = 0;
+  } 
+  mcp.setChannelValue(channel, o);
+}
+
+ISR(TIMER1_COMPA_vect){ // called once every beat
+  beat = true;
+}
+
+
+void loop() {
+  float mod;
+  int o;
+  long now = millis();
+  if( beat ) {
+    beat = false;
+    if( pitch[s] > -1 ) {
+      notestart = millis();
+      notedur = round(beat_m * dur[s]);
+      noteOn(pitch[s]);
+      noteon = true;
+    }
+    s += 1;
+    if( s == phrase ) {
+      s = 0;
+      barstart = notestart;
+    }
+  } else {
+    if( noteon ) {
+        set_mod(MCP4728_CHANNEL_C, mod_note(now - notestart));
+      if( now - notestart > notedur ) {
+        noteOff();
+        noteon = false;
+      }
+    }
+    set_mod(MCP4728_CHANNEL_D, mod_bar(now - barstart));
+    slew += round((float)(target - slew) * slewk);
+    if( slew > 4095 ) {
+      slew = 4095;
+    }
+    if( slew < 0 ) {
+      slew = 0;
+    }
+    mcp.setChannelValue(MCP4728_CHANNEL_A, slew);
+  }
+}
+
+
+void noteOn(int note) {
+  if( note > -1 ) {
+    //mcp.setChannelValue(MCP4728_CHANNEL_A, tuning[note]);
+    target = tuning[note];
+    mcp.setChannelValue(MCP4728_CHANNEL_B, 4095);
+  }
+}
+
+void noteOff() {
+    mcp.setChannelValue(MCP4728_CHANNEL_B, 0);
+}
+
+

README.md

@@ -99,5 +99,27 @@ reverb
 
 Using the Fibonacci series modulo n, also known as the (Pisano period)[https://en.wikipedia.org/wiki/Pisano_period], as a wavetable, and incrementing n for each note in the sequence
 
+### 21 Jacob's Ladder
 
+Deliberate FM synthesis by using a wavetable as the control voltage of a VCO
 
+### 22 Onomatopoeia
+
+Triggering LFO patterns from the sequencer
+
+### 23 Ha Ha
+
+Using the triggering stuff from 22 to build a track with more structure
+
+### 24 Wander
+
+Another 7TET piece using the sequencer
+
+### 25 Ribosome
+
+Using the sequencer to trigger envelopes and LFOs at two scales - notes and
+bars
+
+### 26
+
+Basic slew / portamento