isl6423_write
err = isl6423_write(isl6423, reg_3);
err = isl6423_write(isl6423, reg_4);
err = isl6423_write(isl6423, reg_3);
err = isl6423_write(isl6423, reg_4);
err = isl6423_write(isl6423, reg_3);
err = isl6423_write(isl6423, reg_3);
err = isl6423_write(isl6423, reg_2);