Refactored prepare() method in Audio library

hardware/arduino/sam/libraries/Audio/Audio.cpp

@@ -33,6 +33,17 @@ void AudioClass::end() {
 	free( buffer);
 }
 
+void AudioClass::prepare(int16_t *buffer, int S, int volume){
+    uint16_t *ubuffer = (uint16_t*) buffer;
+    for (int i=0; i<S; i++) {
+        // set volume amplitude (signed multiply)
+        buffer[i] = buffer[i] * volume / 1024;
+        // convert from signed 16 bit to unsigned 12 bit for DAC.
+        ubuffer[i] += 0x8000;
+        ubuffer[i] >>= 4;
+    }
+}
+
 size_t AudioClass::write(const uint32_t *data, size_t size) {
 	const uint32_t TAG = 0x10000000;
 	int i;

hardware/arduino/sam/libraries/Audio/Audio.h

@@ -18,6 +18,7 @@
 class AudioClass : public Print {
 public:
 	AudioClass(DACClass &_dac) : dac(&_dac) { };
+	void prepare(int16_t *buffer, int S, int volume);
 	void begin(uint32_t sampleRate, uint32_t msPreBuffer);
 	void end();
 

hardware/arduino/sam/libraries/Audio/examples/SimpleAudioPlayer/SimpleAudioPlayer.ino

@@ -44,8 +44,8 @@ void loop()
     myFile.read(buffer, sizeof(buffer));
 
     // Prepare samples
-    int volume = analogRead(2);
+    int volume = 1024;
-    prepare(buffer, S, volume);
+    Audio.prepare(buffer, S, volume);
     // Feed samples to audio
     Audio.write(buffer, S);
 
@@ -58,20 +58,7 @@ void loop()
   }
   myFile.close();
 
-
   Serial.println("End of file. Thank you for listening!");
   while (true) ;
 }
 
-
-void prepare(int16_t *buffer, int S, int volume) {
-  uint16_t *ubuffer = (uint16_t*) buffer;
-  for (int i=0; i<S; i++) {
-    // set volume amplitude (signed multiply)
-    buffer[i] = buffer[i] * volume / 1024;
-    // convert from signed 16 bit to unsigned 12 bit for DAC.
-    ubuffer[i] += 0x8000;
-    ubuffer[i] >>= 4;
-  }
-}
-