anchor.diff:  -behaviour(gen_server).
   
   %% API
  --export([start_link/2,
  +-export([start_link/1,
            release/1,
            write/2,
            read/1,
  
positive.code: %% value_change(_, _) ->
  %%   no_change.
  
  
  %%% Local Variables:
  %%% erlang-indent-level: 2
  %%% End:
  
negative.code: %% process spawned.
  %% @todo Add init for exclusive pins
  %% @end
  -spec start_link({pin(), pin_direction()}) ->
                      {'ok', pid()} | 'ignore' | {'error', term()}.
  start_link({Pin, Direction}) ->
    case gproc:lookup_local_name(pname(Pin)) of
      undefined ->
        gen_server:start_link(?MODULE, [Pin, Direction], []);
  