bh1780_write
ret = bh1780_write(bh1780, BH1780_REG_CONTROL, BH1780_PON);
ret = bh1780_write(bh1780, BH1780_REG_CONTROL, BH1780_POFF);
ret = bh1780_write(bh1780, BH1780_REG_CONTROL, BH1780_POFF);
ret = bh1780_write(bh1780, BH1780_REG_CONTROL, BH1780_PON);
return bh1780_write(bh1780, (u8)reg, (u8)writeval);