import processing.serial.*;


Serial port;
float val = 0;

void setup()
{
  size(200, 200);
  //println(Serial.list());
  port = new Serial(this, Serial.list()[1], 9600);
  stroke(255);
  framerate(30);
}

void draw()
{
    background(51);
    val = val - 1;
  if (val < 0)
  {
    val = height;
  }
  line(0, val, width, val);
  if (val > 100 && val < 120)
  {
    port.write("B");
  }
  else
  {
    port.write("C");
  }
}