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#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <termios.h>

#include <unistd.h>

#include <stdio.h>

#define SAMPLES_PER_PLOT 200

int main(int argc, char* argv[]) {

    int input;

    FILE* gnuplot;

    int i;

    float out_data;

    unsigned char buf[SAMPLES_PER_PLOT];

    unsigned char trig = 128;

    unsigned freq = 1000;

    input = open("/dev/midi1", O_RDONLY);

    gnuplot = popen("gnuplot", "w");

    fprintf(gnuplot, "set yrange [-0.1:5.1]\n");

    while(1) {

        // Wait for trig

        do {

            if (read(input, buf, 1) != 1) return 0;

        } while (buf[0] >= trig);

        do {

            if (read(input, buf, 1) != 1) return 0;

        } while (buf[0] < trig);

        // Read rest of the buffer

        for (i=1; i<SAMPLES_PER_PLOT; i++) {

            if (read(input, buf+i, 1) != 1) return 0;

        }

        //read(input, buf+i, SAMPLES_PER_PLOT-1);

        fprintf(gnuplot, "plot '-' with lines\n");

        for (i=0; i<SAMPLES_PER_PLOT; i++) {

            out_data = buf[i]*5.0/256;

            fprintf(gnuplot, "%g %g\n", (float)i/freq, out_data);

        }

        fprintf(gnuplot, "e\n"); // Display output

        fflush(gnuplot);

    }

    close(input);

    pclose(gnuplot);

    printf("\n");

    return 0;

}