wave_player.cpp

00001 //-----------------------------------------------------------------------------
00002 // a sample mbed library to play back wave files.
00003 //
00004 // explanation of wave file format.
00005 // https://ccrma.stanford.edu/courses/422/projects/WaveFormat/
00006 
00007 // if VERBOSE is uncommented then the wave player will enter a verbose
00008 // mode that displays all data values as it reads them from the file
00009 // and writes them to the DAC.  Very slow and unusable output on the DAC,
00010 // but useful for debugging wave files that don't work.
00011 //#define VERBOSE
00012 
00013 
00014 #include <mbed.h>
00015 #include <stdio.h>
00016 #include "pinout.h"
00017 #include <wave_player.h>
00018 
00019 
00020 //-----------------------------------------------------------------------------
00021 // constructor -- accepts an mbed pin to use for AnalogOut.  Only p18 will work
00022 wave_player::wave_player(AnalogOut *_dac, PwmOut *_pwm)
00023 {
00024   wave_PWM = _pwm;
00025   wave_DAC=_dac;
00026   wave_DAC->write_u16(32768);        //DAC is 0-3.3V, so idles at ~1.6V
00027   *wave_PWM = 32768;
00028   verbosity=0;
00029 }
00030 
00031 //-----------------------------------------------------------------------------
00032 // if verbosity is set then wave player enters a mode where the wave file
00033 // is decoded and displayed to the screen, including sample values put into
00034 // the DAC FIFO, and values read out of the DAC FIFO by the ISR.  The DAC output
00035 // itself is so slow as to be unusable, but this might be handy for debugging
00036 // wave files that don't play
00037 //-----------------------------------------------------------------------------
00038 void wave_player::set_verbosity(int v)
00039 {
00040   verbosity=v;
00041 }
00042 
00043 //-----------------------------------------------------------------------------
00044 // player function.  Takes a pointer to an opened wave file.  The file needs
00045 // to be stored in a filesystem with enough bandwidth to feed the wave data.
00046 // LocalFileSystem isn't, but the SDcard is, at least for 22kHz files.  The
00047 // SDcard filesystem can be hotrodded by increasing the SPI frequency it uses
00048 // internally.
00049 //-----------------------------------------------------------------------------
00050 void wave_player::play(FILE *wavefile)
00051 {
00052         unsigned chunk_id,chunk_size,channel;
00053         unsigned data,samp_int,i;
00054         short unsigned dac_data;
00055         long long slice_value;
00056         char *slice_buf;
00057         short *data_sptr;
00058         unsigned char *data_bptr;
00059         int *data_wptr;
00060         FMT_STRUCT wav_format;
00061         long slice,num_slices;
00062   DAC_wptr=0;
00063   DAC_rptr=0;
00064   for (i=0;i<256;i+=2) {
00065     DAC_fifo[i]=0;
00066     DAC_fifo[i+1]=3000;
00067   }
00068   DAC_wptr=4;
00069   DAC_on=0;
00070 
00071   fread(&chunk_id,4,1,wavefile);
00072   fread(&chunk_size,4,1,wavefile);
00073   while (!feof(wavefile)) {
00074     if (verbosity)
00075       printf("Read chunk ID 0x%x, size 0x%x\n",chunk_id,chunk_size);
00076     switch (chunk_id) {
00077       case 0x46464952:
00078         fread(&data,4,1,wavefile);
00079         if (verbosity) {
00080           printf("RIFF chunk\n");
00081           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00082           printf("  RIFF type 0x%x\n",data);
00083         }
00084         break;
00085       case 0x20746d66:
00086         fread(&wav_format,sizeof(wav_format),1,wavefile);
00087         if (verbosity) {
00088           printf("FORMAT chunk\n");
00089           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00090           printf("  compression code %d\n",wav_format.comp_code);
00091           printf("  %d channels\n",wav_format.num_channels);
00092           printf("  %d samples/sec\n",wav_format.sample_rate);
00093           printf("  %d bytes/sec\n",wav_format.avg_Bps);
00094           printf("  block align %d\n",wav_format.block_align);
00095           printf("  %d bits per sample\n",wav_format.sig_bps);
00096         }
00097         if (chunk_size > sizeof(wav_format))
00098           fseek(wavefile,chunk_size-sizeof(wav_format),SEEK_CUR);
00099         break;
00100       case 0x61746164:
00101 // allocate a buffer big enough to hold a slice
00102         slice_buf=(char *)malloc(wav_format.block_align);
00103         if (!slice_buf) {
00104           printf("Unable to malloc slice buffer");
00105           exit(1);
00106         }
00107         num_slices=chunk_size/wav_format.block_align;
00108         samp_int=1000000/(wav_format.sample_rate);
00109         if (verbosity) {
00110           printf("DATA chunk\n");
00111           printf("  chunk size %d (0x%x)\n",chunk_size,chunk_size);
00112           printf("  %d slices\n",num_slices);
00113           printf("  Ideal sample interval=%d\n",(unsigned)(1000000.0/wav_format.sample_rate));
00114           printf("  programmed interrupt tick interval=%d\n",samp_int);
00115         }
00116 
00117 // starting up ticker to write samples out -- no printfs until tick.detach is called
00118         if (verbosity)
00119           tick.attach_us(this,&wave_player::dac_out, 500000); 
00120         else
00121           tick.attach_us(this,&wave_player::dac_out, samp_int); 
00122         DAC_on=1; 
00123 
00124 // start reading slices, which contain one sample each for however many channels
00125 // are in the wave file.  one channel=mono, two channels=stereo, etc.  Since
00126 // mbed only has a single AnalogOut, all of the channels present are averaged
00127 // to produce a single sample value.  This summing and averaging happens in
00128 // a variable of type signed long long, to make sure that the data doesn't
00129 // overflow regardless of sample size (8 bits, 16 bits, 32 bits).
00130 //
00131 // note that from what I can find that 8 bit wave files use unsigned data,
00132 // while 16 and 32 bit wave files use signed data
00133 //
00134         for (slice=0;slice<num_slices;slice+=1) {
00135           fread(slice_buf,wav_format.block_align,1,wavefile);
00136           if (feof(wavefile)) {
00137             printf("Oops -- not enough slices in the wave file\n");
00138             exit(1);
00139           }
00140           data_sptr=(short *)slice_buf;     // 16 bit samples
00141           data_bptr=(unsigned char *)slice_buf;     // 8 bit samples
00142           data_wptr=(int *)slice_buf;     // 32 bit samples
00143           slice_value=0;
00144           for (channel=0;channel<wav_format.num_channels;channel++) {
00145             switch (wav_format.sig_bps) {
00146               case 16:
00147                 if (verbosity)
00148                   printf("16 bit channel %d data=%d ",channel,data_sptr[channel]);
00149                 slice_value+=data_sptr[channel];
00150                 break;
00151               case 32:
00152                 if (verbosity)
00153                   printf("32 bit channel %d data=%d ",channel,data_wptr[channel]);
00154                 slice_value+=data_wptr[channel];
00155                 break;
00156               case 8:
00157                 if (verbosity)
00158                   printf("8 bit channel %d data=%d ",channel,(int)data_bptr[channel]);
00159                 slice_value+=data_bptr[channel];
00160                 break;
00161             }
00162           }
00163           slice_value/=wav_format.num_channels;
00164           
00165 // slice_value is now averaged.  Next it needs to be scaled to an unsigned 16 bit value
00166 // with DC offset so it can be written to the DAC.
00167           switch (wav_format.sig_bps) {
00168             case 8:     slice_value<<=8;
00169                         break;
00170             case 16:    slice_value+=32768;
00171                         break;
00172             case 32:    slice_value>>=16;
00173                         slice_value+=32768;
00174                         break;
00175           }
00176           dac_data=(short unsigned)slice_value;
00177           if (verbosity)
00178             printf("sample %d wptr %d slice_value %d dac_data %u\n",slice,DAC_wptr,(int)slice_value,dac_data);
00179           DAC_fifo[DAC_wptr]=dac_data;
00180           DAC_wptr=(DAC_wptr+1) & 0xff;
00181           while (DAC_wptr==DAC_rptr) {
00182           }
00183         }
00184         DAC_on=0;
00185         tick.detach();
00186         free(slice_buf);
00187         break;
00188       case 0x5453494c:
00189         if (verbosity)
00190           printf("INFO chunk, size %d\n",chunk_size);
00191         fseek(wavefile,chunk_size,SEEK_CUR);
00192         break;
00193       default:
00194         printf("unknown chunk type 0x%x, size %d\n",chunk_id,chunk_size);
00195         data=fseek(wavefile,chunk_size,SEEK_CUR);
00196         break;
00197     }
00198     fread(&chunk_id,4,1,wavefile);
00199     fread(&chunk_size,4,1,wavefile);
00200   }
00201 }
00202 
00203 
00204 void wave_player::dac_out()
00205 {
00206   if (DAC_on) {
00207 #ifdef VERBOSE
00208   printf("ISR rdptr %d got %u\n",DAC_rptr,DAC_fifo[DAC_rptr]);
00209 #endif
00210 //    wave_DAC->write_u16(DAC_fifo[DAC_rptr]);
00211     wave_player::covox_out(DAC_fifo[DAC_rptr]);
00212     wave_PWM->write(float(DAC_fifo[DAC_rptr]/65536.0));
00213     DAC_rptr=(DAC_rptr+1) & 0xff;
00214   }
00215 }
00216 
00217 void wave_player::covox_out(int covox)
00218 {
00219 R0 = (covox>>7)        & 1;
00220 R1 = (covox >> 8)   & 1;
00221 R2 = (covox >> 9)   & 1;
00222 R3 = (covox >> 10)   & 1;
00223 R4 = (covox >> 11)   & 1;
00224 R5 = (covox >> 12)   & 1;
00225 R6 = (covox >> 13)   & 1;
00226 R7 = (covox >> 14)   & 1;
00227 R8 = (covox >> 15)   & 1;
00228 //R9 = ((covox) & 1) | ((covox >> 1) & 1) | ((covox >> 2) & 1);
00229 }