anchor.diff:  
   
   %%
  +%% Test Read the value of the gpio pin, return a boolean value
  +%%
  +-spec read_bool(GpioPinRef :: pid()) -> true | false.
  +
  +read_bool(GpioPinRef) ->
  +  case read(GpioPinRef) of
  +    1  -> true;
  +    0 -> false
  +  end.
  +
  +
  +
  +%%
   %% Test Read the value of the GPIO pin
   %%
   -spec read(GpioRef :: pid()) -> 0 | 1 | {error, atom()}.
  
positive.code:                     'ok' | {'error', atom()}.
  
  set_int(GpioRef, Condition) -> gpio:set_int(GpioRef, Condition).
  
  
  %%
  
negative.code:           start_link/2,
            register_int/1,
            set_int/2,
            read_bool/1,
            read/1,
            write/2,
            stop/1
  