#include <SPI.h>
#include <SD.h>                                       // SD card library
#include "TMRpcm.h"                                   // For reading WAV audio files



#ifdef __arm__
// should use uinstd.h to define sbrk but Due causes a conflict
extern "C" char* sbrk(int incr);
#else  // __ARM__
extern char *__brkval;
#endif  // __arm__


#define audioIn A0                                    // audio input port
#define CS_PIN 53                                     // sd card setup
#define WINDOW_SIZE 160

const double samplingFrequency = 4000; //Hz, must be less than 10000 due to ADC
const double refreshRate = 20; //Hz

unsigned int sampling_period_us;
unsigned long usampling_microseconds;

int16_t vReal[WINDOW_SIZE];

File root;
TMRpcm audio;




/*
These values can be changed in order to evaluate the functions
*/
#define CHANNEL A0


void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  sampling_period_us = round(1000000*(1.0/samplingFrequency));              // change based on our design 

  Serial.print("Initializing SD card...");

  if (!SD.begin(CS_PIN)) {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");

  printfreeMem(0);
 
 
  
  delay(2000);         // wait for initializing

 
  analogReference(DEFAULT);  

  audio.speakerPin = 0;  // set speaker output to pin 0 -> used to read .wav file                              
 
  audio.setVolume(5);    //   0 to 7. Set volume level
  audio.quality(0);      //  Set 1 for 2x oversampling Set 0 for normal
  
   Serial.println("done!");
}




void loop(void) {
 
  if ( !audio.isPlaying() ) {
      File entry = SD.open("PinkPanther30.wav");
      audio.play( entry.name() );      // play the audio file
      Serial.print("Playing file: ");
      Serial.println( entry.name() );
  }  
  /*SAMPLING*/
 
  usampling_microseconds = micros();
  
  for(int i=0; i< WINDOW_SIZE; i++)     // check for /2
  {
      vReal[i] = analogRead(audioIn);       // reading from A0
      while(micros() - usampling_microseconds < sampling_period_us){
        //empty loop
      }
      usampling_microseconds += sampling_period_us;
  }

 printfreeMem(3);

  byte buffer[2 * WINDOW_SIZE];
  
    for (int i = 0; i < WINDOW_SIZE; i++) {
        int16_t sample = vReal[i];
        buffer[2 * i] = lowByte(sample);
        buffer[2 * i + 1] = highByte(sample);
      }
      Serial.write(buffer, 2 * WINDOW_SIZE);



  while(1);

}



//MEMORY LIMITATIONS???
//https://forum.arduino.cc/t/arduino-uno-ssd1306-allocation-failed-need-help-downsizing/604698/5
//https://cdn-learn.adafruit.com/downloads/pdf/memories-of-an-arduino.pdf
//https://www.instructables.com/Playing-Wave-file-using-arduino/
//https://simple-circuit.com/arduino-wave-audio-player-sd-card/


void printfreeMem(int index) {
   Serial.print("Freemem ");
   Serial.print(index);
   Serial.print(": ");
   Serial.println(freeMemory());
}


int freeMemory() {
  char top;
#ifdef __arm__
  return &top - reinterpret_cast<char*>(sbrk(0));
#elif defined(CORE_TEENSY) || (ARDUINO > 103 && ARDUINO != 151)
  return &top - __brkval;
#else  // __arm__
  return __brkval ? &top - __brkval : &top - __malloc_heap_start;
#endif  // __arm__
}