code: function read(mode,callback) {
        if (spi === undefined) {return;};
        var txBuf = new Buffer([1,mode,0]);
        var rxBuf = new Buffer([0,0,0]);
        
        spi.transfer(txBuf,rxBuf,function(dev,buffer) {
          var value = ((buffer[1] & 3)<< 8) + buffer[2];
          callback(value);
        });
      }
docs: lit l'interface spi