   Change the serial port configuration after `open/3` has been called. See
   `open/3` for the valid options.
   """
-  @spec configure(pid, [uart_option]) :: :ok | {:error, term}
+  @spec configure(GenServer.server, [uart_option]) :: :ok | {:error, term}
   def configure(pid, opts) do
     GenServer.call(pid, {:configure, opts})
   end

    * `:ebadf` - the UART is closed
    * `:einval` - the UART is in active mode
  """
  @spec read(pid, integer) :: {:ok, binary} | {:error, term}
  def read(pid, timeout \\ 5000) do
    GenServer.call(pid, {:read, timeout}, genserver_timeout(timeout))
  end

  Close the serial port. The GenServer continues to run so that a port can
  be opened again.
  """
  @spec close(GenServer.server) :: :ok | {:error, term}
  def close(pid) do
    GenServer.call(pid, :close)
  end
