AD7173_REG_CH
ret = ad_sd_write_reg(&st->sd, AD7173_REG_CH(i), 2, 0);
return ad_sd_write_reg(&st->sd, AD7173_REG_CH(channel), 2, val);
ret = ad_sd_write_reg(sd, AD7173_REG_CH(i), 2, 0);
return ad_sd_write_reg(sd, AD7173_REG_CH(chan), 2, 0);