AD_ADDR
write_i2c_reg(pd->regs, AD_ADDR, AD_CMD_REG);
write_i2c_reg(pd->regs, AD_ADDR, 0);
write_i2c_reg(pd->regs, AD_ADDR, AD_CMD_REG);
write_i2c_reg(pd->regs, AD_ADDR, AD_POS_REF);
write_i2c_reg(pd->regs, AD_ADDR, AD_NEG_REF);
write_i2c_reg(pd->regs, AD_ADDR, AD_CMD_REG);