GRCAN_CTRL_ENABLE
grcan_write_reg(®s->ctrl, GRCAN_CTRL_ENABLE);
if (grcan_read_bits(®s->ctrl, GRCAN_CTRL_ENABLE))
grcan_clear_bits(®s->ctrl, GRCAN_CTRL_ENABLE);
grcan_write_reg(®s->ctrl, GRCAN_CTRL_ENABLE);