     {:noreply, pin_map}
   end
 
-  defp blink(pid, delay_during \\ 500, delay_after \\ 500) do
+  defp blink(pid, delay_during \\ @delay_during, delay_after \\ @delay_after) do
     Gpio.write(pid, 1)
     :timer.sleep(delay_during)
     Gpio.write(pid, 0)

           fn letter ->
             case Map.fetch(pin_map, to_string([letter])) do
               {:ok, pid} ->
                 blink(pid, 500, 500)
               _ ->
                 :timer.sleep(1000)
             end
           end
         )

  end

  ## server callbacks

  @delay_during        500
  @delay_after         500
  @delay_nonprinting  1000

  def init(:ok) do
    {
