anchor.diff:  % API
   -export([start_link/1]).
   -export([raw/0]).
  --export([raw/1]).
   -export([g/0]).
  --export([g/1]).
   
   % Callbacks
   -export([init/1]).
  
positive.code:     grisp_spi:send_recv(Slot, Req),
      {ok, #state{slot = Slot}}.
  
  handle_call({raw, Opts}, _From, State) ->
      Raw = xyz(State#state.slot, Opts),
      {reply, Raw, State};
  handle_call({g, Opts}, _From, State) ->
      Raw = xyz(State#state.slot, Opts),
      {reply, scale(State#state.mode, Raw), State}.
  
  handle_cast(Request, _State) -> error({unknown_cast, Request}).
  
  
negative.code: 
  start_link(Slot) -> gen_server:start_link(?MODULE, Slot, []).
  
  raw() ->
      {_Mode, Result} = call(raw),
      Result.
  
  g() ->
      {Mode, Result} = call(raw),
      scale(Mode, Result).
  
  %--- Callbacks -----------------------------------------------------------------
  
  