File content as of revision 0:143457f10e26:

//todo red button and light sensor


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

AnalogOut DACout(p18);
DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);
DigitalOut led4(LED4);
DigitalOut digout(p8);
Ticker tick;
SDFileSystem sd(p5, p6, p7, p13, "sd");

#define SAMPLE_FREQ 40000
#define BUF_SIZE (SAMPLE_FREQ/10)
#define SLICE_BUF_SIZE 1

void dac_out(void);
void play_wave(char *);
void cleanup(char *);
void fill_adc_buf(short *, unsigned);
void swapword(unsigned *);

// a FIFO for the DAC
short DAC_fifo[256];
short DAC_wptr;
short DAC_rptr;
short DAC_on;

typedef struct uFMT_STRUCT {
  short comp_code;
  short num_channels;
  unsigned sample_rate;
  unsigned avg_Bps;
  short block_align;
  short sig_bps;
} FMT_STRUCT;


int main() {
  led1=0; wait(.5); led1=1; wait(.5); led1=0;
  printf("Hello, world!\n");
  play_wave("/sd/baddonut.wav");
  printf("Back from play_wave()\n");
  play_wave("/sd/clint16.wav");
  printf("Back from play_wave()\n");
  printf("Goodbye, world!\n");
}
  
void play_wave(char *wavname)
{
        unsigned chunk_id,chunk_size,channel;
        unsigned *data_wptr,data,samp_int,i;
        short dac_data;
        char *slice_buf;
        short *data_sptr;
        char *data_bptr;
        FMT_STRUCT wav_format;
        FILE *wavfile;
        long slice,num_slices;
  DAC_wptr=0;
  DAC_rptr=0;
  for (i=0;i<256;i+=2) {
    DAC_fifo[i]=0;
    DAC_fifo[i+1]=3000;
  }
  DAC_wptr=4;
  DAC_on=0;

  led1=led2=led3=led4=0;
  
  printf("Playing wave file '%s'\n",wavname);

  wavfile=fopen(wavname,"rb");
  if (!wavfile) {
    printf("Unable to open wav file '%s'\n",wavname);
    exit(1);
  }

  fread(&chunk_id,4,1,wavfile);
  fread(&chunk_size,4,1,wavfile);
  while (!feof(wavfile)) {
    printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size);
    switch (chunk_id) {
      case 0x46464952:
        fread(&data,4,1,wavfile);
        printf("RIFF chunk\n");
        printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
        printf("  RIFF type 0x%x\n",data);
        break;
      case 0x20746d66:
        fread(&wav_format,sizeof(wav_format),1,wavfile);
        printf("FORMAT chunk\n");
        printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
        printf("  compression code %d\n",wav_format.comp_code);
        printf("  %d channels\n",wav_format.num_channels);
        printf("  %d samples/sec\n",wav_format.sample_rate);
        printf("  %d bytes/sec\n",wav_format.avg_Bps);
        printf("  block align %d\n",wav_format.block_align);
        printf("  %d bits per sample\n",wav_format.sig_bps);
        if (chunk_size > sizeof(wav_format))
          fseek(wavfile,chunk_size-sizeof(wav_format),SEEK_CUR);
// create a slice buffer large enough to hold multiple slices
        slice_buf=(char *)malloc(wav_format.block_align*SLICE_BUF_SIZE);
        if (!slice_buf) {
          printf("Unable to malloc slice buffer");
          exit(1);
        }
        break;
      case 0x61746164:
        slice_buf=(char *)malloc(wav_format.block_align*SLICE_BUF_SIZE);
        if (!slice_buf) {
          printf("Unable to malloc slice buffer");
          exit(1);
        }        num_slices=chunk_size/wav_format.block_align;
        printf("DATA chunk\n");
        printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
        printf("  %d slices\n",num_slices);
        printf("  Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate));
        samp_int=1000000/(wav_format.sample_rate);
        printf("  programmed interrupt tick interval=%d\n",samp_int);

// starting up ticker to write samples out -- no printfs until tick.detach is called
        tick.attach_us(&dac_out, samp_int); 
        DAC_on=1; 
        led2=1;
        for (slice=0;slice<num_slices;slice+=SLICE_BUF_SIZE) {
          fread(slice_buf,wav_format.block_align*SLICE_BUF_SIZE,1,wavfile);
          if (feof(wavfile)) {
            printf("Oops -- not enough slices in the wave file\n");
            exit(1);
          }
          data_sptr=(short *)slice_buf;
          for (i=0;i<SLICE_BUF_SIZE;i++) {
            dac_data=0;

// for a stereo wave file average the two channels.
            for (channel=0;channel<wav_format.num_channels;channel++) {
              switch (wav_format.sig_bps) {
                case 16:
                  dac_data+=(  ((int)(*data_sptr++)) +32768)>>5;
                  break;
              }
            }
            dac_data>>=1;
            DAC_fifo[DAC_wptr]=dac_data;
            DAC_wptr=(DAC_wptr+1) & 0xff;
            while (DAC_wptr==DAC_rptr) {
              led1=1;
            }
            led1=0;
          }
        }
        DAC_on=0;
        led2=0;
        tick.detach();
        printf("Ticker detached\n");
        led3=1;
        free(slice_buf);
        break;
      case 0x5453494c:
        printf("INFO chunk, size %d\n",chunk_size);
        fseek(wavfile,chunk_size,SEEK_CUR);
        break;
      default:
        printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
        data=fseek(wavfile,chunk_size,SEEK_CUR);
        break;
    }
    fread(&chunk_id,4,1,wavfile);
    fread(&chunk_size,4,1,wavfile);
  }
  printf("Done with wave file\n");
  fclose(wavfile);
  led1=0;
}


void dac_out()
{
  if (DAC_on) {
    digout=1;
    DACout.write(DAC_fifo[DAC_rptr]);
    DAC_rptr=(DAC_rptr+1) & 0xff;
    digout=0;
  }
}