sound: first try

README.md

@@ -54,6 +54,9 @@ pip install -U platformio
 platformio run -t upload && platformio device monitor -b 115200
 ```
 
+* Convert mp3 files: `sox ~/Music/input.mp3 -c 1 -r 11025 output.wav trim 0 30`
+* SD card is tested with one FAT16 partion
+
 ## ToDo
 * Prototype
 * Keypad layout

src/main.cpp

@@ -18,6 +18,8 @@ Keyboard keyboard;
 SDCard sdcard;
 Sound sound;
 
+uint16_t buffer[2048];
+
 void setup()
 {
   // initialize LED digital pin as an output.
@@ -32,6 +34,21 @@ void setup()
   keyboard.init();
   sdcard.mount();
   sound.init();
+  sdcard.open("/sabaton.wav");
+  int num_bytes_i = 0;
+  int num_bytes_o = 0;
+  while (sdcard.available()) {
+    num_bytes_i += sdcard.read(buffer, 2048);
+    num_bytes_o += sound.render_sample_block(buffer, buffer, 2048);
+    Serial.print(".");
+  }
+  sdcard.close();
+  Serial.println("");
+  Serial.print(num_bytes_i,DEC);
+  Serial.println(" bytes read from file");
+  Serial.print(num_bytes_o,DEC);
+  Serial.println(" bytes written to i2s");
+  delay(1000);
 }
 
 void loop()

src/sdcard.cpp

@@ -11,6 +11,7 @@
 #include "SPI.h"
 
 #include "sdcard.h"
+#include "sound.h"
 
 using namespace std;
 
@@ -55,15 +56,22 @@ void SDCard::umount() {
     SD.end();
 }
 
-void SDCard::readFile(const char *path){
-    File file = fs.open(path);
+void SDCard::open(const char *path) {
+    file = fs.open(path);
     if(!file){
         Serial.println("Failed to open file for reading");
         return;
     }
+}
 
-    Serial.print("Read from file: ");
-    while(file.available()){
-        Serial.write(file.read());
-    }
+void SDCard::close() {
+  file.close();
+}
+
+bool SDCard::available() {
+  return file.available();
+}
+
+size_t SDCard::read(uint16_t *buffer, size_t len){
+  return file.read((uint8_t *)buffer, len);
 }

src/sdcard.h

@@ -11,11 +11,15 @@ class SDCard {
     SDCard();
     void mount();
     void umount();
-    void readFile(const char *path);
+    void open(const char *path);
+    void close();
+    size_t read(uint16_t *buffer, size_t len);
+    bool available();
   private:
     fs::FS &fs = SD;
     uint8_t cardType;
     uint64_t cardSize;
+    File file;
 };
 
 #endif /* _SDCARD_H */

src/sound.cpp

@@ -17,7 +17,7 @@
 #include <math.h>
 
 
-#define SAMPLE_RATE     (36000)
+#define SAMPLE_RATE     (11025)
 #define WAVE_FREQ_HZ    (100)
 //#define PI 3.14159265
 
@@ -88,12 +88,17 @@ void Sound::end() {
 
 /* callback(?) for new audio data */
 int Sound::render_sample_block(uint16_t *sample_buf_left, uint16_t *sample_buf_right, int num_samples) {
+  TickType_t delay = 10 / portTICK_PERIOD_MS; // max delay: 10ms instead of portMAX_DELAY
   int num_pushed_samples = 0;
   for (int i=0; i < num_samples; i++) {
     unsigned int sample = ((unsigned short) sample_buf_left[i] << 16 & 0xffff0000) | ((unsigned short) sample_buf_right[i]);
-    int num_pushed_bytes = i2s_push_sample(i2s_num, (char *)&sample, portMAX_DELAY);
-    if (num_pushed_bytes > 0) num_pushed_samples += num_pushed_bytes;
-    else break;
+    int num_pushed_bytes = i2s_push_sample(i2s_num, (char *)&sample, delay);
+    if (num_pushed_bytes > 0) {
+      num_pushed_samples += num_pushed_bytes;
+    } else {
+      Serial.println("i2s buffer filled");
+      break;
+    }
   }
   return num_pushed_samples;
 }