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  1. #include <sys/types.h>
  2. #include <sys/stat.h>
  3. #include <fcntl.h>
  4. #include <termios.h>
  5. #include <unistd.h>
  6. #include <stdio.h>
  7.  
  8. #define DEVICE "/dev/midi1"
  9. #define BAUDRATE B115200
  10. #define TRIG_LEVEL 128
  11. #define SAMPLE_FREQ 1000
  12.  
  13. #define SAMPLES_PER_PLOT 200
  14.  
  15. struct termios oldtio,newtio;
  16.  
  17. int main(int argc, char* argv[]) {
  18.     int input;
  19.     FILE* gnuplot;
  20.     int i;
  21.     float out_data;
  22.     unsigned char buf[SAMPLES_PER_PLOT];
  23.     unsigned char trig = TRIG_LEVEL;
  24.     unsigned freq = SAMPLE_FREQ;
  25.    
  26.     input = open(DEVICE, O_RDONLY | O_NOCTTY);
  27.     if (input <0) {perror(DEVICE); return -1; }
  28.     gnuplot = popen("gnuplot", "w");
  29.    
  30.     tcgetattr(input,&oldtio); /* save current port settings */
  31.    
  32.     // bzero not defined? moving newtio outside main to zero it.
  33.     //bzero(&newtio, sizeof(newtio));
  34.     newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
  35.     newtio.c_iflag = IGNPAR;
  36.     newtio.c_oflag = 0;
  37.    
  38.     /* set input mode (non-canonical, no echo,...) */
  39.     newtio.c_lflag = 0;
  40.    
  41.     newtio.c_cc[VTIME]    = 0;   /* inter-character timer unused */
  42.     newtio.c_cc[VMIN]     = SAMPLES_PER_PLOT;   /* blocking read until all samples received */
  43.    
  44.     tcflush(input, TCIFLUSH);
  45.     tcsetattr(input,TCSANOW,&newtio);
  46.    
  47.     fprintf(gnuplot, "set yrange [-0.1:5.1]\n");
  48.     while(1) {
  49.         // Wait for trig
  50.         do {
  51.             if (read(input, buf, 1) != 1) return 0;
  52.         } while (buf[0] >= trig);
  53.         do {
  54.             if (read(input, buf, 1) != 1) return 0;
  55.         } while (buf[0] < trig);
  56.        
  57.         // Read rest of the buffer
  58.         for (i=1; i<SAMPLES_PER_PLOT; i++) {
  59.             if (read(input, buf+i, 1) != 1) return 0;
  60.         }
  61.         //read(input, buf+i, SAMPLES_PER_PLOT-1);
  62.        
  63.         fprintf(gnuplot, "plot '-' with lines\n");
  64.        
  65.         for (i=0; i<SAMPLES_PER_PLOT; i++) {
  66.             out_data = buf[i]*5.0/256;
  67.             fprintf(gnuplot, "%g %g\n", (float)i/freq, out_data);
  68.         }
  69.         fprintf(gnuplot, "e\n"); // Display output
  70.         fflush(gnuplot);
  71.     }
  72.    
  73.     tcsetattr(input,TCSANOW,&oldtio);
  74.     close(input);
  75.     pclose(gnuplot);
  76.     printf("\n");
  77.     return 0;
  78. }
  79.