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: 
  %% @doc write data into an i2c slave device.
  %% @end
  -spec(write(channel(), addr(), data(), len()) -> ok | {error, reason}).
  write(Channel, Addr, Data, Len) ->
      gen_server:call(Channel, {call, write, Addr, Data, Len}).
  
  %% @doc read data from an i2c slave device.
  %% @end
  
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, []).
  