MBED Example: How to play WAV sound file from SDCard using SPI and AnalogOut

.from: https://github.com/leroilion/mbed/blob/master/PlayMusic/Examples/PlayMusic/main.cpp

#include "mbed.h"
#include "SDFileSystem.h"

SDFileSystem sd(11, 12, 13, 14, "sd");
AnalogOut aout(18);

int main() {
 int ch;   //first read byte
 int ch2;  //second read byte
 int dat;  //combined 16 bit word for DtoA

 FILE *fp = fopen("/sd/QI2.wav", "r"); //open File to read
 if(fp == NULL) {error("Could not open file for write\n");}

 while(!feof(fp)) {  //Play the music until End Of File
  dat = 0;
  ch = fgetc(fp);  //get first  byte
  ch2 =fgetc(fp);  //get second byte
  ch = ch << 8;    //shift bits 8 places to left 
  dat = ch2 | ch;  //combine bits to single 16 bit int 
  aout.write_u16((unsigned short)(dat)); //DtoA conversion
  wait_us(88); //set for 11k sample rate
  }

 fclose(fp); //close the file

}