anchor.diff:  
   %% @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}).
  +-spec(write(channel(), addr(), data()) -> ok | {error, reason}).
  +write(Channel, Addr, Data) ->
  +    gen_server:call(Channel, {call, write, Addr, Data}).
   
   %% @doc read data from an i2c slave device.
   %% @end
  
positive.code: 
  %% API
  -export([start_link/1, stop/1]).
  -export([write/4, read/3]).
  
  %% gen_server callbacks
  -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
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, []).
  