anchor.diff:  %% 1> grisp_gpio:clear(led1_r).
   %% <<>>
   %% '''
  +- spec clear(pin()) -> any().
   clear(Pin) -> gen_server:call(?MODULE, {command, <<(index(Pin)):8, 3:8>>}).
   
  -%% @doc Sets the given pin to true
  +%% @doc Sets a pin to `true'.
   %%
   %% === Example ===
   %% Turn on the red led of `led_1' with:
  
positive.code: %% 3> grisp_gpio:set(led1_r).
  %% <<>>
  %% '''
  set(Pin) -> gen_server:call(?MODULE, {command, <<(index(Pin)):8, 4:8>>}).
  
  
  
negative.code:     gen_server:start_link({local, ?MODULE}, ?MODULE, DriverMod, []).
  
  %% @equiv configure(Pin, Type, [default])
  -spec configure(pin(), pin_type()) -> any().
  configure(Pin, Type) -> configure(Pin, Type, [default]).
  
  %% @doc Configure pin type.
  -spec configure(pin(), pin_type(), [default]) -> any().
  configure(Pin, Type, Attr) ->
      Command = <<(index(Pin)):8, 1:8, (map_type(Type)):8, (map_attr(Attr)):8>>,
      gen_server:call(?MODULE, {command, Command}).
  
  %% @doc Configure slot.
  %%
  %% The GPIO slots can be configured with `{T1, T2, T3, T4}'
  %% and the SPI slots allow the configuration `disable_cs | enable_cs'.
  -spec configure_slot(Slot::slot(),
                       Config::{T1::pin_type(), T2::pin_type(), T3::pin_type(), T4::pin_type()}
                          | disable_cs | enable_cs) -> ok.
  configure_slot(gpio1, {T1, T2, T3, T4}) ->
      configure(gpio1_1, T1),
      configure(gpio1_2, T2),
  