#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int main(void) {
    //printf("hello world\n");
    FILE *output;
    u_int8_t  angle;
    if ((output = fopen("/dev/ttyS0", "wb")) == NULL) { 
        printf("Unable to open serial port\n");
    }
    /* marker */
    while(1){
        for (angle=0; angle < 254; angle++) {
            fputc(255, output);
            fputc(2, output);
            fputc(128+128*(sin(angle*(6.28/255.0))), output);
            usleep(10000);
            fflush(output);
        }
    }
    fclose(output);
    return 0;
}