wip

output_devices/I2S/hello.MAX98357A.RP2040.2.ino

+//
+// hello.MAX98357A.RP2040.2.ino
+//    XIAO RP2040 MAX98357A I2S amp two-voice hello-world
+//    overclock at 150 MHz
+//
+// Neil Gershenfeld 11/7/24
+//
+// This work may be reproduced, modified, distributed,
+// performed, and displayed for any purpose, but must
+// acknowledge this project. Copyright is retained and
+// must be preserved. The work is provided as is; no
+// warranty is provided, and users accept all liability.
+//
+
+#include <I2S.h>
+
+#define clock 1
+#define frame (clock+1)
+#define data 4
+#define sample_rate 22050.0
+#define sample_bits 16
+#define notes_length 138
+#define note_length 0.18
+
+// 0 ... 40	= Middle C, 49 = A440
+float pitches[] = {0,27.50000,29.13524,30.86771,32.70320,34.64783,36.70810,38.89087,
+  41.20344,43.65353,46.24930,48.99943,51.91309,55.00000,58.27047,61.73541,65.40639,
+  69.29566,73.41619,77.78175,82.40689,87.30706,92.49861,97.99886,103.8262,110.0000,
+  116.5409,123.4708,130.8128,138.5913,146.8324,155.5635,164.8138,174.6141,184.9972,
+  195.9977,207.6523,220.0000,233.0819,246.9417,261.6256,277.1826,293.6648,311.1270,
+  329.6276,349.2282,369.9944,391.9954,415.3047,440.0000,466.1638,493.8833,523.2511,
+  554.3653,587.3295,622.2540,659.2551,698.4565,739.9888,783.9909,830.6094,880.0000,
+  932.3275,987.7666,1046.502,1108.731,1174.659,1244.508,1318.510,1396.913,1479.978,
+  1567.982,1661.219,1760.000,1864.655,1975.533,2093.005,2217.461,2349.318,2489.016,
+  2637.020,2793.826,2959.955,3135.963,3322.438,3520.000,3729.310,3951.066,4186.009};
+
+// from J.S. Bach Invention No. 8
+int part1[] = {
+  0,0,0,45,45,49,49,45,45,52,52,45,45,
+  57,57,56,54,52,54,52,50,49,50,49,47,
+  45,45,49,49,52,52,49,49,57,57,52,52,
+  61,64,62,64,61,64,62,64,61,64,62,64,
+  57,61,59,61,57,61,59,61,57,61,59,61,
+  54,57,56,57,54,57,56,57,54,57,56,57,
+  51,51,47,47,54,54,51,51,57,57,54,54,
+  59,61,59,57,56,57,56,54,52,54,52,50,
+  49,49,54,52,51,52,51,49,47,49,47,45,
+  44,45,44,42,40,40,52,51,52,52,44,44,
+  45,45,52,52,44,44,52,52,42,42,51,51,
+  52,52,52,52,0,0,0
+};
+
+// from J.S. Bach Invention No. 8
+int part2[] = {
+  0,0,0,0,0,0,0,0,0,0,0,0,0,
+  0,0,33,33,37,37,33,33,40,40,33,33,
+  45,45,44,42,40,42,40,38,37,38,37,35,
+  33,33,37,37,40,40,37,37,45,45,40,40,
+  49,52,50,52,49,52,50,52,49,52,50,52,
+  45,49,47,49,45,49,47,49,45,49,47,49,
+  42,45,44,45,42,45,44,45,42,45,44,45,
+  39,39,35,35,40,40,35,35,44,44,40,40,
+  45,47,45,44,42,44,42,40,39,40,39,37,
+  35,35,40,39,37,39,37,35,33,35,33,32,
+  30,32,30,28,35,33,32,33,35,35,23,23,
+  0,0,0,0,0,0,0
+};
+
+I2S i2s(OUTPUT);
+
+void setup() {
+  i2s.setBCLK(clock);
+  i2s.setDATA(data);
+  i2s.setBitsPerSample(sample_bits);
+  i2s.begin(sample_rate);
+  }
+
+void loop() {
+  float t=0;
+  float dt = 1/sample_rate;
+  int16_t sample,oldsample;
+  //
+  // loop over notes
+  //
+  for (int note = 1; note < (notes_length-1); ++note) {
+    float pitch1 = pitches[part1[note]];
+    float pitch2 = pitches[part2[note]];
+    float amplitude1 = 13000-10*pitch1;
+    float amplitude2 = 13000-10*pitch2;
+    float tend = t+note_length;
+    float amp1,amp2;
+    //
+    // loop over samples
+    //
+    while (t < tend) {
+      t += dt;
+      //
+      // taper amplitude at start and end on new notes to eliminate pops
+      //
+      if ((tend-t) > ((0.9*note_length)) && (part1[note] != part1[note-1]))
+        amp1 = amplitude1*((1-(tend-t)/note_length)/(1-0.9));
+      else if (((tend-t) < (0.1*note_length)) && (part1[note] != part1[note+1]))
+        amp1 = amplitude1*(((tend-t)/note_length)/0.1);
+      else
+        amp1 = amplitude1;
+      if ((tend-t) > ((0.9*note_length)) && (part2[note] != part2[note-1]))
+        amp2 = amplitude2*((1-(tend-t)/note_length)/(1-0.9));
+      else if (((tend-t) < (0.1*note_length)) && (part2[note] != part2[note+1]))
+        amp2 = amplitude2*(((tend-t)/note_length)/0.1);
+      else
+        amp2 = amplitude2;
+      sample = amp1*1*sin(2*PI*t*pitch1)+amp2*1*sin(2*PI*t*pitch2);
+      //
+      // output left and right samples 
+      //
+      i2s.write(sample);
+      i2s.write(sample);
+      }
+    }
+  }