anchor.diff:      {ok, #state{driver = {DriverMod, Ref}}}.
   
   % @private
  -handle_call({msgs, Enc_msgs}, _From, State) ->
  +handle_call({msgs, EncodedMsgs}, _From, State) ->
       {DriverMod, Ref} = State#state.driver,
  -    Resp = DriverMod:command(Ref, Enc_msgs),
  -    {reply, Resp, State}.
  +    RespList = [maybe_send_msgs(Msg, DriverMod, Ref) || Msg <- EncodedMsgs],
  +    LastResp = lists:last(RespList),
  +    {reply, LastResp, State}.
   
   % @private
   handle_cast(Request, _State) -> error({unknown_cast, Request}).
  
positive.code:     gen_server:start_link({local, ?MODULE}, ?MODULE, DriverMod, []).
  
  msgs([Adr | Msgs]) ->
      do_msgs(Adr, Msgs).
  
  %--- Callbacks -----------------------------------------------------------------
  
  
negative.code:     Data_len = byte_size(W),
      Msg_count = byte_size(M) div 8,
      <<Data_len:16, W/binary, Msg_count:16, M/binary>>.
  
  maybe_send_msgs({sleep, Time}, _DriverMod, _Ref) ->
      timer:sleep(Time);
  maybe_send_msgs(Msg, DriverMod, Ref) ->
      DriverMod:command(Ref, Msg).
  