Making a spark fun mp3 shield v15 and Hiletgo 2.2" TFT ILI9341 display work together on Mega 2560

Hi,

I tried to make my topic title as clear as possible, that way you'll see i'm, again, one of these guy who try to make an mp3 player kind of thing. In fact we are trying with my wife to make a story box for our daughter (and future kids) with stories that'll be telled by all the family.

That said, i have a sparkfun mp3 shield (this one) an Hiletgo TFT screen (this one) and an arduino mega2560.

My problem is that, independently, each part works. The example sketch/libraries given by sparkfun on the tutorial works without a problem, and the screen works with the library i found in this instructable.

There's the diagram of my project. I didn't put the resistors needed for the screen to operate in it, but they are on my breadbord doing the job.

When i load each sketch, i can make things works separately (everything connected as in the diagram), i have no problem using the serial monitor and send command to make the player play songs, raise the volume etc. When in try to mix them, the screen works, everything seems to show up in the serial monitor concerning the MP3 but when i send a command, nothing happen, and then, randomly, maybe 30 seconds later, the serial monitor shows the command have been sent, the screen goes blank and show some artefacts, and then the player start (not always) to play music.

There's the code.

/**
 * \file FilePlayer.ino
 *
 * \brief Example sketch of using the MP3Shield Arduino driver, with flexible list of files and formats
 * \remarks comments are implemented with Doxygen Markdown format
 *
 * \author Bill Porter
 * \author Michael P. Flaga
 *
 * This sketch listens for commands from a serial terminal (such as the Serial
 * Monitor in the Arduino IDE). Listening for either a single character menu
 * commands or an numeric strings of an index. Pointing to a music file, found
 * in the root of the SdCard, to be played. A list of index's and corresponding
 * files in the root can be listed out using the 'l' (little L) command.
 *
 * This sketch allows the various file formats to be played: mp3, aac, wma, wav,
 * fla & mid.
 *
 * This sketch behaves nearly identical to MP3Shield_Library_Demo.ino, but has
 * extra complicated loop() as to recieve string of characters to create the
 * file index. As the Serial Monitor is typically default with no CR or LF, this
 * sketch uses intercharacter time out as to determine when a full string has
 * has been entered to be processed.
 */
#define TFT_CLK 52
#define TFT_MISO 50
#define TFT_MOSI 51
#define TFT_DC 48
#define TFT_CS 47
#define TFT_RST 44
#define CS 53

//Add the SdFat Libraries
#include <SdFat.h>
#include <FreeStack.h>

#include <Adafruit_GFX_AS.h>    // Core graphics library
#include <Adafruit_ILI9341_AS.h> // Hardware-specific library
#include <SPI.h>
#include <Load_fonts.h>
#include <Run_faster.h>
#include <TFT_ILI9341.h>

Adafruit_ILI9341_AS tft = Adafruit_ILI9341_AS(TFT_CS, TFT_DC, TFT_RST);

//and the MP3 Shield Library
#include <SFEMP3Shield.h>

// Below is not needed if interrupt driven. Safe to remove if not using.
#if defined(USE_MP3_REFILL_MEANS) && USE_MP3_REFILL_MEANS == USE_MP3_Timer1
  #include <TimerOne.h>
#elif defined(USE_MP3_REFILL_MEANS) && USE_MP3_REFILL_MEANS == USE_MP3_SimpleTimer
  #include <SimpleTimer.h>
#endif

/**
 * \brief Object instancing the SdFat library.
 *
 * principal object for handling all SdCard functions.
 */
SdFat sd;

/**
 * \brief Object instancing the SFEMP3Shield library.
 *
 * principal object for handling all the attributes, members and functions for the library.
 */
SFEMP3Shield MP3player;
int16_t last_ms_char; // milliseconds of last recieved character from Serial port.
int8_t buffer_pos; // next position to recieve character from Serial port.

unsigned long targetTime = 0;
byte red = 31;
byte green = 0;
byte blue = 0;
byte state = 0;
unsigned int colour = red << 11;

//------------------------------------------------------------------------------
/**
 * \brief Setup the Arduino Chip's feature for our use.
 *
 * After Arduino's kernel has booted initialize basic features for this
 * application, such as Serial port and MP3player objects with .begin.
 * Along with displaying the Help Menu.
 *
 * \note returned Error codes are typically passed up from MP3player.
 * Whicn in turns creates and initializes the SdCard objects.
 *
 * \see
 * \ref Error_Codes
 */
  char buffer[6]; // 0-35K+null

void setup() {
  
  tft.init();
  tft.setRotation(1);

  uint8_t result; //result code from some function as to be tested at later time.

  Serial.begin(115200);

  Serial.print(F("F_CPU = "));
  Serial.println(F_CPU);
  Serial.print(F("Free RAM = ")); // available in Version 1.0 F() bases the string to into Flash, to use less SRAM.
  Serial.print(FreeStack(), DEC);  // FreeRam() is provided by SdFatUtil.h
  Serial.println(F(" Should be a base line of 1017, on ATmega328 when using INTx"));


  //Initialize the SdCard.
  if(!sd.begin(SD_SEL, SPI_FULL_SPEED)) sd.initErrorHalt();
  // depending upon your SdCard environment, SPI_HAVE_SPEED may work better.
  if(!sd.chdir("/")) sd.errorHalt("sd.chdir");

  //Initialize the MP3 Player Shield
  result = MP3player.begin();
  //check result, see readme for error codes.
  if(result != 0) {
    Serial.print(F("Error code: "));
    Serial.print(result);
    Serial.println(F(" when trying to start MP3 player"));
    if( result == 6 ) {
      Serial.println(F("Warning: patch file not found, skipping.")); // can be removed for space, if needed.
      Serial.println(F("Use the \"d\" command to verify SdCard can be read")); // can be removed for space, if needed.
    }
  }

#if (0)
  // Typically not used by most shields, hence commented out.
  Serial.println(F("Applying ADMixer patch."));
  if(MP3player.ADMixerLoad("admxster.053") == 0) {
    Serial.println(F("Setting ADMixer Volume."));
    MP3player.ADMixerVol(-3);
  }
#endif

  help();
  last_ms_char = millis(); // stroke the inter character timeout.
  buffer_pos = 0; // start the command string at zero length.
  parse_menu('l'); // display the list of files to play

}

//------------------------------------------------------------------------------
/**
 * \brief Main Loop the Arduino Chip
 *
 * This is called at the end of Arduino kernel's main loop before recycling.
 * And is where the user's serial input of bytes are read and analyzed by
 * parsed_menu.
 *
 * Additionally, if the means of refilling is not interrupt based then the
 * MP3player object is serviced with the availaible function.
 *
 * \note Actual examples of the libraries public functions are implemented in
 * the parse_menu() function.
 */
void loop() {

  tft.setTextSize(1);
    tft.fillScreen(ILI9341_BLACK);
    tft.setTextColor(ILI9341_GREEN);

    tft.drawString(" !\"#$%&'()*+,-./0123456",0,0,2);
    tft.drawString("789:;<=>?@ABCDEFGHIJKL",0,16,2);
    tft.drawString("MNOPQRSTUVWXYZ[\\]^_`",0,32,2);
    tft.drawString("abcdefghijklmnopqrstuvw",0,48,2);
    int xpos=0;
    xpos+=tft.drawString("xyz{|}~",0,64,2);
    tft.drawChar(127,xpos,64,2);
    delay(4000);


// Below is only needed if not interrupt driven. Safe to remove if not using.
#if defined(USE_MP3_REFILL_MEANS) \
    && ( (USE_MP3_REFILL_MEANS == USE_MP3_SimpleTimer) \
    ||   (USE_MP3_REFILL_MEANS == USE_MP3_Polled)      )

  MP3player.available();
#endif

  char inByte;
  if (Serial.available() > 0) {
    inByte = Serial.read();
    if ((0x20 <= inByte) && (inByte <= 0x126)) { // strip off non-ASCII, such as CR or LF
      if (isDigit(inByte)) { // macro for ((inByte >= '0') && (inByte <= '9'))
        // else if it is a number, add it to the string
        buffer[buffer_pos++] = inByte;
      } else {
        // input char is a letter command
        buffer_pos = 0;
        parse_menu(inByte);
      }
      buffer[buffer_pos] = 0; // update end of line
      last_ms_char = millis(); // stroke the inter character timeout.
    }
  } else if ((millis() - last_ms_char) > 500 && ( buffer_pos > 0 )) {
    // ICT expired and have something
    if (buffer_pos == 1) {
      // look for single byte (non-number) menu commands
      parse_menu(buffer[buffer_pos - 1]);

    } else if (buffer_pos > 5) {
      // dump if entered command is greater then uint16_t
      Serial.println(F("Ignored, Number is Too Big!"));

    } else {
      // otherwise its a number, scan through files looking for matching index.
      int16_t fn_index = atoi(buffer);
      SdFile file;
      char filename[13];
      sd.chdir("/",true);
      uint16_t count = 1;
      while (file.openNext(sd.vwd(),O_READ))
      {
        file.getName(filename, sizeof(filename));
        if ( isFnMusic(filename) ) {

          if (count == fn_index) {
            Serial.print(F("Index "));
            SerialPrintPaddedNumber(count, 5 );
            Serial.print(F(": "));
            Serial.println(filename);
            Serial.print(F("Playing filename: "));
            Serial.println(filename);
            int8_t result = MP3player.playMP3(filename);
            //check result, see readme for error codes.
            if(result != 0) {
              Serial.print(F("Error code: "));
              Serial.print(result);
              Serial.println(F(" when trying to play track"));
            }
            char title[30]; // buffer to contain the extract the Title from the current filehandles
            char artist[30]; // buffer to contain the extract the artist name from the current filehandles
            char album[30]; // buffer to contain the extract the album name from the current filehandles
            MP3player.trackTitle((char*)&title);
            MP3player.trackArtist((char*)&artist);
            MP3player.trackAlbum((char*)&album);

            //print out the arrays of track information
            Serial.write((byte*)&title, 30);
            Serial.println();
            Serial.print(F("by:  "));
            Serial.write((byte*)&artist, 30);
            Serial.println();
            Serial.print(F("Album:  "));
            Serial.write((byte*)&album, 30);
            Serial.println();
            break;
          }
          count++;
        }
        file.close();
      }

    }

    //reset buffer to start over
    buffer_pos = 0;
    buffer[buffer_pos] = 0; // delimit
  }

  delay(100);
}

uint32_t  millis_prv;

//------------------------------------------------------------------------------
/**
 * \brief Decode the Menu.
 *
 * Parses through the characters of the users input, executing corresponding
 * MP3player library functions and features then displaying a brief menu and
 * prompting for next input command.
 */
void parse_menu(byte key_command) {

  uint8_t result; // result code from some function as to be tested at later time.

  // Note these buffer may be desired to exist globably.
  // but do take much space if only needed temporarily, hence they are here.
  char title[30]; // buffer to contain the extract the Title from the current filehandles
  char artist[30]; // buffer to contain the extract the artist name from the current filehandles
  char album[30]; // buffer to contain the extract the album name from the current filehandles

  Serial.print(F("Received command: "));
  Serial.write(key_command);
  Serial.println(F(" "));

  //if s, stop the current track
  if(key_command == 's') {
    Serial.println(F("Stopping"));
    MP3player.stopTrack();

  //if 1-9, play corresponding track
  } else if(key_command >= '1' && key_command <= '9') {
    //convert ascii numbers to real numbers
    key_command = key_command - 48;

#if USE_MULTIPLE_CARDS
    sd.chvol(); // assign desired sdcard's volume.
#endif
    //tell the MP3 Shield to play a track
    result = MP3player.playTrack(key_command);

    //check result, see readme for error codes.
    if(result != 0) {
      Serial.print(F("Error code: "));
      Serial.print(result);
      Serial.println(F(" when trying to play track"));
    } else {

      Serial.println(F("Playing:"));

      //we can get track info by using the following functions and arguments
      //the functions will extract the requested information, and put it in the array we pass in
      MP3player.trackTitle((char*)&title);
      MP3player.trackArtist((char*)&artist);
      MP3player.trackAlbum((char*)&album);

      //print out the arrays of track information
      Serial.write((byte*)&title, 30);
      Serial.println();
      Serial.print(F("by:  "));
      Serial.write((byte*)&artist, 30);
      Serial.println();
      Serial.print(F("Album:  "));
      Serial.write((byte*)&album, 30);
      Serial.println();
    }

  //if +/- to change volume
  } else if((key_command == '-') || (key_command == '+')) {
    union twobyte mp3_vol; // create key_command existing variable that can be both word and double byte of left and right.
    mp3_vol.word = MP3player.getVolume(); // returns a double uint8_t of Left and Right packed into int16_t

    if(key_command == '-') { // note dB is negative
      // assume equal balance and use byte[1] for math
      if(mp3_vol.byte[1] >= 254) { // range check
        mp3_vol.byte[1] = 254;
      } else {
        mp3_vol.byte[1] += 2; // keep it simpler with whole dB's
      }
    } else {
      if(mp3_vol.byte[1] <= 2) { // range check
        mp3_vol.byte[1] = 2;
      } else {
        mp3_vol.byte[1] -= 2;
      }
    }
    // push byte[1] into both left and right assuming equal balance.
    MP3player.setVolume(mp3_vol.byte[1], mp3_vol.byte[1]); // commit new volume
    Serial.print(F("Volume changed to -"));
    Serial.print(mp3_vol.byte[1]>>1, 1);
    Serial.println(F("[dB]"));

  //if < or > to change Play Speed
  } else if((key_command == '>') || (key_command == '<')) {
    uint16_t playspeed = MP3player.getPlaySpeed(); // create key_command existing variable
    // note playspeed of Zero is equal to ONE, normal speed.
    if(key_command == '>') { // note dB is negative
      // assume equal balance and use byte[1] for math
      if(playspeed >= 254) { // range check
        playspeed = 5;
      } else {
        playspeed += 1; // keep it simpler with whole dB's
      }
    } else {
      if(playspeed == 0) { // range check
        playspeed = 0;
      } else {
        playspeed -= 1;
      }
    }
    MP3player.setPlaySpeed(playspeed); // commit new playspeed
    Serial.print(F("playspeed to "));
    Serial.println(playspeed, DEC);

  /* Alterativly, you could call a track by it's file name by using playMP3(filename);
  But you must stick to 8.1 filenames, only 8 characters long, and 3 for the extension */
  } else if(key_command == 'f' || key_command == 'F') {
    uint32_t offset = 0;
    if (key_command == 'F') {
      offset = 2000;
    }

    //create a string with the filename
    char trackName[] = "track001.mp3";

#if USE_MULTIPLE_CARDS
    sd.chvol(); // assign desired sdcard's volume.
#endif
    //tell the MP3 Shield to play that file
    result = MP3player.playMP3(trackName, offset);
    //check result, see readme for error codes.
    if(result != 0) {
      Serial.print(F("Error code: "));
      Serial.print(result);
      Serial.println(F(" when trying to play track"));
    }

  /* Display the file on the SdCard */
  } else if(key_command == 'd') {
    if(!MP3player.isPlaying()) {
      // prevent root.ls when playing, something locks the dump. but keeps playing.
      // yes, I have tried another unique instance with same results.
      // something about SdFat and its 500byte cache.
      Serial.println(F("Files found (name date time size):"));
      sd.ls(LS_R | LS_DATE | LS_SIZE);
    } else {
      Serial.println(F("Busy Playing Files, try again later."));
    }

  /* Get and Display the Audio Information */
  } else if(key_command == 'i') {
    MP3player.getAudioInfo();

  } else if(key_command == 'p') {
    if( MP3player.getState() == playback) {
      MP3player.pauseMusic();
      Serial.println(F("Pausing"));
    } else if( MP3player.getState() == paused_playback) {
      MP3player.resumeMusic();
      Serial.println(F("Resuming"));
    } else {
      Serial.println(F("Not Playing!"));
    }

  } else if(key_command == 't') {
    int8_t teststate = MP3player.enableTestSineWave(126);
    if(teststate == -1) {
      Serial.println(F("Un-Available while playing music or chip in reset."));
    } else if(teststate == 1) {
      Serial.println(F("Enabling Test Sine Wave"));
    } else if(teststate == 2) {
      MP3player.disableTestSineWave();
      Serial.println(F("Disabling Test Sine Wave"));
    }

  } else if(key_command == 'S') {
    Serial.println(F("Current State of VS10xx is."));
    Serial.print(F("isPlaying() = "));
    Serial.println(MP3player.isPlaying());

    Serial.print(F("getState() = "));
    switch (MP3player.getState()) {
    case uninitialized:
      Serial.print(F("uninitialized"));
      break;
    case initialized:
      Serial.print(F("initialized"));
      break;
    case deactivated:
      Serial.print(F("deactivated"));
      break;
    case loading:
      Serial.print(F("loading"));
      break;
    case ready:
      Serial.print(F("ready"));
      break;
    case playback:
      Serial.print(F("playback"));
      break;
    case paused_playback:
      Serial.print(F("paused_playback"));
      break;
    case testing_memory:
      Serial.print(F("testing_memory"));
      break;
    case testing_sinewave:
      Serial.print(F("testing_sinewave"));
      break;
    }
    Serial.println();

   } else if(key_command == 'b') {
    Serial.println(F("Playing Static MIDI file."));
    MP3player.SendSingleMIDInote();
    Serial.println(F("Ended Static MIDI file."));

#if !defined(__AVR_ATmega32U4__)
  } else if(key_command == 'm') {
      uint16_t teststate = MP3player.memoryTest();
    if(teststate == -1) {
      Serial.println(F("Un-Available while playing music or chip in reset."));
    } else if(teststate == 2) {
      teststate = MP3player.disableTestSineWave();
      Serial.println(F("Un-Available while Sine Wave Test"));
    } else {
      Serial.print(F("Memory Test Results = "));
      Serial.println(teststate, HEX);
      Serial.println(F("Result should be 0x83FF."));
      Serial.println(F("Reset is needed to recover to normal operation"));
    }

  } else if(key_command == 'e') {
    uint8_t earspeaker = MP3player.getEarSpeaker();
    if(earspeaker >= 3){
      earspeaker = 0;
    } else {
      earspeaker++;
    }
    MP3player.setEarSpeaker(earspeaker); // commit new earspeaker
    Serial.print(F("earspeaker to "));
    Serial.println(earspeaker, DEC);

  } else if(key_command == 'r') {
    MP3player.resumeMusic(2000);

  } else if(key_command == 'R') {
    MP3player.stopTrack();
    MP3player.vs_init();
    Serial.println(F("Reseting VS10xx chip"));

  } else if(key_command == 'g') {
    int32_t offset_ms = 20000; // Note this is just an example, try your own number.
    Serial.print(F("jumping to "));
    Serial.print(offset_ms, DEC);
    Serial.println(F("[milliseconds]"));
    result = MP3player.skipTo(offset_ms);
    if(result != 0) {
      Serial.print(F("Error code: "));
      Serial.print(result);
      Serial.println(F(" when trying to skip track"));
    }

  } else if(key_command == 'k') {
    int32_t offset_ms = -1000; // Note this is just an example, try your own number.
    Serial.print(F("moving = "));
    Serial.print(offset_ms, DEC);
    Serial.println(F("[milliseconds]"));
    result = MP3player.skip(offset_ms);
    if(result != 0) {
      Serial.print(F("Error code: "));
      Serial.print(result);
      Serial.println(F(" when trying to skip track"));
    }

  } else if(key_command == 'O') {
    MP3player.end();
    Serial.println(F("VS10xx placed into low power reset mode."));

  } else if(key_command == 'o') {
    MP3player.begin();
    Serial.println(F("VS10xx restored from low power reset mode."));

  } else if(key_command == 'D') {
    uint16_t diff_state = MP3player.getDifferentialOutput();
    Serial.print(F("Differential Mode "));
    if(diff_state == 0) {
      MP3player.setDifferentialOutput(1);
      Serial.println(F("Enabled."));
    } else {
      MP3player.setDifferentialOutput(0);
      Serial.println(F("Disabled."));
    }

  } else if(key_command == 'V') {
    MP3player.setVUmeter(1);
    Serial.println(F("Use \"No line ending\""));
    Serial.print(F("VU meter = "));
    Serial.println(MP3player.getVUmeter());
    Serial.println(F("Hit Any key to stop."));

    while(!Serial.available()) {
      union twobyte vu;
      vu.word = MP3player.getVUlevel();
      Serial.print(F("VU: L = "));
      Serial.print(vu.byte[1]);
      Serial.print(F(" / R = "));
      Serial.print(vu.byte[0]);
      Serial.println(" dB");
      delay(1000);
    }
    Serial.read();

    MP3player.setVUmeter(0);
    Serial.print(F("VU meter = "));
    Serial.println(MP3player.getVUmeter());

  } else if(key_command == 'T') {
    uint16_t TrebleFrequency = MP3player.getTrebleFrequency();
    Serial.print(F("Former TrebleFrequency = "));
    Serial.println(TrebleFrequency, DEC);
    if (TrebleFrequency >= 15000) { // Range is from 0 - 1500Hz
      TrebleFrequency = 0;
    } else {
      TrebleFrequency += 1000;
    }
    MP3player.setTrebleFrequency(TrebleFrequency);
    Serial.print(F("New TrebleFrequency = "));
    Serial.println(MP3player.getTrebleFrequency(), DEC);

  } else if(key_command == 'E') {
    int8_t TrebleAmplitude = MP3player.getTrebleAmplitude();
    Serial.print(F("Former TrebleAmplitude = "));
    Serial.println(TrebleAmplitude, DEC);
    if (TrebleAmplitude >= 7) { // Range is from -8 - 7dB
      TrebleAmplitude = -8;
    } else {
      TrebleAmplitude++;
    }
    MP3player.setTrebleAmplitude(TrebleAmplitude);
    Serial.print(F("New TrebleAmplitude = "));
    Serial.println(MP3player.getTrebleAmplitude(), DEC);

  } else if(key_command == 'B') {
    uint16_t BassFrequency = MP3player.getBassFrequency();
    Serial.print(F("Former BassFrequency = "));
    Serial.println(BassFrequency, DEC);
    if (BassFrequency >= 150) { // Range is from 20hz - 150hz
      BassFrequency = 0;
    } else {
      BassFrequency += 10;
    }
    MP3player.setBassFrequency(BassFrequency);
    Serial.print(F("New BassFrequency = "));
    Serial.println(MP3player.getBassFrequency(), DEC);

  } else if(key_command == 'C') {
    uint16_t BassAmplitude = MP3player.getBassAmplitude();
    Serial.print(F("Former BassAmplitude = "));
    Serial.println(BassAmplitude, DEC);
    if (BassAmplitude >= 15) { // Range is from 0 - 15dB
      BassAmplitude = 0;
    } else {
      BassAmplitude++;
    }
    MP3player.setBassAmplitude(BassAmplitude);
    Serial.print(F("New BassAmplitude = "));
    Serial.println(MP3player.getBassAmplitude(), DEC);

  } else if(key_command == 'M') {
    uint16_t monostate = MP3player.getMonoMode();
    Serial.print(F("Mono Mode "));
    if(monostate == 0) {
      MP3player.setMonoMode(1);
      Serial.println(F("Enabled."));
    } else {
      MP3player.setMonoMode(0);
      Serial.println(F("Disabled."));
    }
#endif

  /* List out music files on the SdCard */
  } else if(key_command == 'l') {
    if(!MP3player.isPlaying()) {
      Serial.println(F("Music Files found :"));
      SdFile file;
      char filename[13];
      sd.chdir("/",true);
      uint16_t count = 1;
      while (file.openNext(sd.vwd(),O_READ))
      {
        file.getName(filename, sizeof(filename));
        if ( isFnMusic(filename) ) {
          SerialPrintPaddedNumber(count, 5 );
          Serial.print(F(": "));
          Serial.println(filename);
          count++;
        }
        file.close();
      }
      Serial.println(F("Enter Index of File to play"));

    } else {
      Serial.println(F("Busy Playing Files, try again later."));
    }

  } else if(key_command == 'h') {
    help();
  }

  // print prompt after key stroke has been processed.
  Serial.print(F("Time since last command: "));  
  Serial.println((float) (millis() -  millis_prv)/1000, 2);  
  millis_prv = millis();
  Serial.print(F("Enter s,1-9,+,-,>,<,f,F,d,i,p,t,S,b"));
#if !defined(__AVR_ATmega32U4__)
  Serial.print(F(",m,e,r,R,g,k,O,o,D,V,B,C,T,E,M:"));
#endif
  Serial.println(F(",l,h :"));
}

//------------------------------------------------------------------------------
/**
 * \brief Print Help Menu.
 *
 * Prints a full menu of the commands available along with descriptions.
 */
void help() {
  Serial.println(F("Arduino SFEMP3Shield Library Example:"));
  Serial.println(F(" courtesy of Bill Porter & Michael P. Flaga"));
  Serial.println(F("COMMANDS:"));
  Serial.println(F(" [1-9] to play a track"));
  Serial.println(F(" [f] play track001.mp3 by filename example"));
  Serial.println(F(" [F] same as [f] but with initial skip of 2 second"));
  Serial.println(F(" [s] to stop playing"));
  Serial.println(F(" [d] display directory of SdCard"));
  Serial.println(F(" [+ or -] to change volume"));
  Serial.println(F(" [> or <] to increment or decrement play speed by 1 factor"));
  Serial.println(F(" [i] retrieve current audio information (partial list)"));
  Serial.println(F(" [p] to pause."));
  Serial.println(F(" [t] to toggle sine wave test"));
  Serial.println(F(" [S] Show State of Device."));
  Serial.println(F(" [b] Play a MIDI File Beep"));
#if !defined(__AVR_ATmega32U4__)
  Serial.println(F(" [e] increment Spatial EarSpeaker, default is 0, wraps after 4"));
  Serial.println(F(" [m] perform memory test. reset is needed after to recover."));
  Serial.println(F(" [M] Toggle between Mono and Stereo Output."));
  Serial.println(F(" [g] Skip to a predetermined offset of ms in current track."));
  Serial.println(F(" [k] Skip a predetermined number of ms in current track."));
  Serial.println(F(" [r] resumes play from 2s from begin of file"));
  Serial.println(F(" [R] Resets and initializes VS10xx chip."));
  Serial.println(F(" [O] turns OFF the VS10xx into low power reset."));
  Serial.println(F(" [o] turns ON the VS10xx out of low power reset."));
  Serial.println(F(" [D] to toggle SM_DIFF between inphase and differential output"));
  Serial.println(F(" [V] Enable VU meter Test."));
  Serial.println(F(" [B] Increament bass frequency by 10Hz"));
  Serial.println(F(" [C] Increament bass amplitude by 1dB"));
  Serial.println(F(" [T] Increament treble frequency by 1000Hz"));
  Serial.println(F(" [E] Increament treble amplitude by 1dB"));
#endif
  Serial.println(F(" [l] Display list of music files"));
  Serial.println(F(" [0####] Enter index of file to play, zero pad! e.g. 01-65534"));
  Serial.println(F(" [h] this help"));
}

void SerialPrintPaddedNumber(int16_t value, int8_t digits ) {
  int currentMax = 10;
  for (byte i=1; i<digits; i++){
    if (value < currentMax) {
      Serial.print("0");
    }
    currentMax *= 10;
  }
  Serial.print(value);
}

Now, i think the problem comes from the way i "handle" the SPI pins/BUS, i.e. like a noob. I have connect the mp3 shield on the ISCP header on the mega because it avoid me from having to put all my cables on the breadboard. Pins have been rerouted like suggested in the sparkfun tutorial and i have declared CS pin as 53. I don't know if i made it properly though.

I saw a few pages on the internet speaking/teaching about the SPI BUS, but i didn't manage to find something clear i can wrap my head around. I know there's something in the code i must add, something like "Serial.begin(9600);" somewhere in it, but i'm a bit lost.

In the CPP files available in the libraries i use, i have these lines which are uncommentend, i think it must be this way but i don't know :

#ifdef SPI_HAS_TRANSACTION
static inline void spi_begin(void) __attribute__((always_inline));

static inline void spi_begin(void) {
  SPI.beginTransaction(SPISettings(8000000, MSBFIRST, SPI_MODE0));
}

static inline void spi_end(void) __attribute__((always_inline));

static inline void spi_end(void) {
  SPI.endTransaction();
}

#else
#define spi_begin()
#define spi_end()
#endif

So, here it is, if anyone as any idea on how i can solve my problem, don't hesitate to ask questions, i may have forgot an important piece of information.

Thank you !

In the description of this sparkfun-MP3-Module I found
Supporting the VS1053B is a µSD card socket, which you can use to store MP3 files on. Using the Arduino SD library, it's simple to read music files off an SD card, and stream them to the VS1053B.

Haha it is not simple to
"to read music files off an SD card, and stream them to the VS1053B."

This means your Arduino-Code has to read from the SD-card and forward the datastream towards the MP3-chip.

There are much more comfortable to use MP3-player-moduls on the market.
Sorry Sparkfun the good is the death of the usual.

seeed has a MP3-module
https://wiki.seeedstudio.com/Grove-Serial_MP3_Player/
which does all the reading from SD-card-MP3-files and transforming this MP3-data into an audio-Signal on its own automatically. You the user don't have to care about the bit-banging. Reading from SD-card and doing the bitbanging is done by the MP3-chip itself.

All the customer needs to do is to send serial (=UART) commands to the MP3-module to make the module start/stop play files turn up/down volume etc.

same thing with this module:
http://www.diymalls.com/UART-Control-Serial-MP3-Music-Player-Module-for-UNO-Raspberry-Pi

If Sparkfun can't provide a demo-code that shows how to use their MP3-module in cooperation with a SPI-driven display send it back to them.

My experience with seeed is that they provide good support through libraries etc.
best regards Stefan

Thanks for the response !

I'm going to contact them and see if they can help me.

Maybe there's a workaround by using the RX/TX pins, i'm going to try to dig deeper on that subject.

In any case, if sparkfun can't help me i will consider buying the grove serial.

No you can't use a serial connection as a SPI-interface!
The only workaround I see with the sparkfun-board is what is described in this thread

Some kind of an SPI-compliant mode.

The differents between the sparkfun MP3-Board and the others is:
With the Sparkfun-MP3-Board Your microcontroller has to do the work of reading the data from SD-card and to send this data to the MP3-chip.

With the other boards your microcontroller is unloaded from this work!
reading from SD-card and creating the is done by the MP3-board and your microcontroller is free to do a lot off other stuff.
Streaming MP3-data has to be done continiously which means the SPI-bus has to work all the time. It might be that there will be only very few time left for doing other things with the SPI-bus like sending display-data.

best regards Stefan

Ok. I'm waiting for a response from sparkfun, and if there's no way for me to make them work together, i'll buy a more friendly board.

A big thanks for your time !