I´ve decided to use a different library, one that uses the physical tx and rx pins with a diode, and I´ve got voltages with decimals and other options. It´s on github, called IbusBM or something like that. Only problem is that ibus supports up to 15/16 values, but I haven´t been able to add more than the 3/4 the library comes with. It´s also designed to receive Ibus servo values. I´ll try to mix the library with another Ibus one.