   end
 
   ## server callbacks
+
+  @delay_during        500
+  @delay_after         500
+  @delay_nonprinting  1000
 
   def init(:ok) do
     {

    {:noreply, pin_map}
  end

  defp blink(pid, delay_during \\ 500, delay_after \\ 500) 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)
               _ ->
                 :timer.sleep(@delay_nonprinting)
             end
           end
         )
