anchor.diff:  
   %% API
   -export([start_link/1, stop/1]).
  --export([write/4, read/3]).
  +-export([write/3, read/3]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code: %%                                   {stop, Reason, State}
  %% @end
  %%--------------------------------------------------------------------
  handle_call({call, write, Addr, Data, Len}, _From, State) ->
      case port_lib:sync_call_to_port(State, {i2c_write, Addr, Data, Len}) < 0 of
  	true ->
  	    Reply = {error, i2c_write_error};
  
negative.code: %%% API
  %%%===================================================================
  
  %% @doc
  %% Starts the server
  %% @end
  -spec(start_link({channel(), devname()}) -> {ok, pid()} | {error, reason}).
  start_link({Channel, Devname}) ->
      gen_server:start_link({local, Channel}, ?MODULE, Devname, []).
  