#define N 200
float stab[N];

#define HARM 20
float ampl[HARM];

float outf[N] = {0.};
unsigned char out[N] = {0};

void setup() {
  DDRD = B11111111;  // sets Arduino pins 0 to 7 as outputs
  for(int i=0; i<N; i++) {
    stab[i] = sin((float)2.*(float)3.1415927*(float)i/(float)N);
  }
  for(int i=0; i<HARM; i++) {
    if(i%2==0) ampl[i] = 1./(i+1);
  }
  float maxs = 0.;
  for(int i=0; i<N; i++) {
    double s=0;
    for(int j=0; j<HARM; j++) {
      s += ampl[j]*stab[i*(j+1) % N];
    }
    if(fabs(s)>maxs) maxs=fabs(s);
    outf[i] = s;
  }
  for(int i=0; i<N; i++) {
    out[i] = (outf[i]/maxs+1)*127.5;
  }
}

void loop() {
  for(int i=0; i<N; i++) {
    PORTD = out[i];
  }
}