Generate DTMF tones

dtmf_generate.c

//
// Generate DTMF tones
//

#include <stdio.h>
#include <math.h>

float OutData[44100];

typedef struct ToneInfo {
   const char *name;
   int tone1;
   int tone2;
} ToneInfo;

ToneInfo TonesToGenerate[] = {
   {"1", 1209, 697},
   {"2", 1336, 697},
   {"3", 1477, 697},
   {"A", 1633, 697},
   {"4", 1209, 770},
   {"5", 1336, 770},
   {"6", 1477, 770},
   {"B", 1633, 770},
   {"7", 1209, 852},
   {"8", 1336, 852},
   {"9", 1477, 852},
   {"C", 1633, 852},
   {"*", 1209, 941},
   {"0", 1336, 941},
   {"#", 1477, 941},
   {"D", 1633, 941}
};

void generate_dtmf(int tone1, int tone2, int rate, float *out)
{
   float increment = (2.0f * M_PI) / ((float)rate / tone1);
   float sampleValue = 0;
   int i;
   
   // Add first tone at half volume
   for (i=0; i<rate; i++) {
      out[i] = sinf(sampleValue) * 0.5;
      sampleValue += increment;
   }

   // Add second tone at half volume
   increment = (2.0f * M_PI) / ((float)rate / tone2);
   sampleValue = 0;
   for (i=0; i<rate; i++) {
      out[i] += sinf(sampleValue) * 0.5;
      sampleValue += increment;
   }
}

int main(int argc, char **argv)
{
   int i;

   // Generate all the tones as 32bit float
   for (i=0; i<sizeof(TonesToGenerate)/sizeof(ToneInfo); i++) {
      char buffer[128];
      sprintf(buffer, "T-%s.raw", TonesToGenerate[i].name);
      FILE *fp = fopen(buffer, "w");
      generate_dtmf(TonesToGenerate[i].tone1, TonesToGenerate[i].tone2, 44100, OutData);
      fwrite(OutData, sizeof(float), 44100, fp);
      fclose(fp);
   }
}