SC16IS7XX_REGISTER_IODIR
error = sc->sc_funcs->read_reg(sc, SC16IS7XX_REGISTER_IODIR, 1, &iodir, 1);
error = sc->sc_funcs->write_reg(sc, SC16IS7XX_REGISTER_IODIR, 1, &iodir, 1);
error = sc->sc_funcs->read_reg(sc, SC16IS7XX_REGISTER_IODIR, 1, &iodir_reg, 1);