From c9584b9b3c8c83decfda3712ad61ca13eb04d94f Mon Sep 17 00:00:00 2001
From: dakkar <dakkar@thenautilus.net>
Date: Fri, 28 Aug 2020 19:42:12 +0100
Subject: using the i2c-to-internal-dac functions, it sounds a bit better

---
 esp32/lego-piano.ino | 63 +++++++++++++++++++++++++++-------------------------
 1 file changed, 33 insertions(+), 30 deletions(-)

diff --git a/esp32/lego-piano.ino b/esp32/lego-piano.ino
index 7901279..8991f07 100644
--- a/esp32/lego-piano.ino
+++ b/esp32/lego-piano.ino
@@ -17,6 +17,7 @@
  */
 
 #include <driver/dac.h>
+#include <driver/i2s.h>
 
 #define TSF_IMPLEMENTATION
 #define TSF_NO_STDIO
@@ -39,27 +40,12 @@ const int ampEnable = 32;
 
 const int octave_shift = 2;
 
+const int sampleRate = 8000;
+
 char pressed[row_count*col_count] = { 0 };
 
-hw_timer_t * timer = NULL;
-portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
 tsf* g_TinySoundFont = 0;
-bool playing = false;
-
-RingBuf<short, 500> buffer;
-
-void IRAM_ATTR onTimer() {
-  if (!g_TinySoundFont) return;
-
-  portENTER_CRITICAL_ISR(&timerMux);
-
-  short sample;
-  if (buffer.pop(sample)) {
-    dac_output_voltage(DAC_CHANNEL_1, sample >> 8);
-  }
-
-  portEXIT_CRITICAL_ISR(&timerMux);
-}
+const i2s_port_t i2sPort = I2S_NUM_0;
 
 void setup() {
   Serial.begin(115200);
@@ -67,9 +53,24 @@ void setup() {
   pinMode(ampEnable, OUTPUT);
   digitalWrite(ampEnable, LOW);
 
-  dac_i2s_disable();
+  dac_i2s_enable();
   dac_output_enable(DAC_CHANNEL_1);
 
+  static const i2s_config_t i2s_config = {
+      .mode = (i2s_mode_t)( I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_DAC_BUILT_IN ),
+      .sample_rate = sampleRate,
+      .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
+      .channel_format = I2S_CHANNEL_FMT_ALL_RIGHT,
+      .intr_alloc_flags = 0, // default interrupt priority
+      .dma_buf_count = 8,
+      .dma_buf_len = 64,
+      .use_apll = false
+  };
+
+  i2s_driver_install(i2sPort, &i2s_config, 0, NULL);
+  i2s_set_dac_mode(I2S_DAC_CHANNEL_RIGHT_EN); // only dac1
+  i2s_set_sample_rates(i2sPort, sampleRate); // ??
+
   for (int i=0;i<row_count;++i) {
     pinMode(rows[i], OUTPUT|PULLUP);
     pinMode(adc[i], INPUT);
@@ -79,19 +80,11 @@ void setup() {
   }
 
   currentLed = 0;
-  playing = false;
 
   g_TinySoundFont = tsf_load_memory(SoundFont, sizeof(SoundFont));
   if (g_TinySoundFont) {
     // render at 5kHz
-    tsf_set_output(g_TinySoundFont, TSF_MONO, 5000, 0);
-
-    // pre-scaling a 40MHz clock by 4k, then calling on every 2 tick,
-    // should give us 5kHz
-    timer = timerBegin(0, 4000, true);
-    timerAttachInterrupt(timer, &onTimer, true);
-    timerAlarmWrite(timer, 2, true);
-    timerAlarmEnable(timer);
+    tsf_set_output(g_TinySoundFont, TSF_MONO, sampleRate, 0);
   }
   else {
     Serial.println("failed to start tsf");
@@ -149,6 +142,7 @@ int sense(int led) {
   return value < 500;
 }
 
+RingBuf<short, 500> buffer;
 short intermediateBuffer[5000];
 
 void loop() {
@@ -159,15 +153,24 @@ void loop() {
 
   enableLed(currentLed);
   unsigned long t = millis();
+  size_t written=100;
+  short value;
+  // fill the I2S buffer
+  while (written > 0) {
+    // we don't want to drop an element from the buffer if we then
+    // can't write it! so we peek at the buffer, try to write, and pop
+    // if successful
+    value=buffer[0];
+    i2s_write(i2sPort, &value, sizeof(value), &written, 0);
+    if (written > 0) buffer.pop(value);
+  }
 
   int toFill = buffer.maxSize() - buffer.size();
   if (toFill > 100) {
     tsf_render_short(g_TinySoundFont, intermediateBuffer, toFill, 0);
-    noInterrupts();
     for (int i=0;i<toFill;++i) {
       buffer.push(intermediateBuffer[i]);
     }
-    interrupts();
   }
 
   while (millis() == t) {
-- 
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