anchor.diff:  
   % API
   -export([open/0, configure/3, configure/4,
  -	 configure_gpio/3, get/2, clear/2, set/2, set/3, clear/3]).
  +	 configure_gpio/3, get/2, clear/2, set/2, set/3, clear/3,
  +         enable_spi_ss1/1, disable_spi_ss1/1]).
   
   %--- API -----------------------------------------------------------------------
   
  
positive.code:     configure(Port, 7, T4).
  
  get(Port, Pin_index) ->
      Port ! {self(), {command, <<Pin_index:8, 2:8>>}}.
  
  clear(Port, Pin_index) ->
      Port ! {self(), {command, <<Pin_index:8, 3:8>>}}.
  
  set(Port, Pin_index) ->
      Port ! {self(), {command, <<Pin_index:8, 4:8>>}}.
  
  set(Port, gpio1, Pin) when 1 =< Pin, Pin =< 4 ->    
      set(Port, Pin - 1);	% 0 .. 3     
  set(Port, gpio2, Pin) when 1 =< Pin, Pin =< 4 ->    
      set(Port, Pin + 3).	% 4 .. 7     
  
  clear(Port, gpio1, Pin) when 1 =< Pin, Pin =< 4 ->    
      clear(Port, Pin - 1);	% 0 .. 3     
  clear(Port, gpio2, Pin) when 1 =< Pin, Pin =< 4 ->    
      clear(Port, Pin + 3).	% 4 .. 7     
  
  map_type(input) ->
      4;
  map_type(output_0) ->				% default value 0
  
negative.code:     configure(Port, Pin_index, Type, [default]).
  
  configure(Port, Pin_index, Type, Attr) ->
      Port ! {self(), {command, <<(index(Pin_index)):8, 1:8, 
  				(map_type(Type)):8, (map_attr(Attr)):8>>}}.
  
  configure_gpio(Port, gpio1, {T1, T2, T3, T4}) ->
  