iadc_do_conversion
ret = iadc_do_conversion(iadc, chan->channel, &adc_raw);
ret = iadc_do_conversion(iadc, IADC_GAIN_17P857MV, &iadc->gain);
ret = iadc_do_conversion(iadc, IADC_INT_OFFSET_CSP2_CSN2,
ret = iadc_do_conversion(iadc, IADC_EXT_OFFSET_CSP_CSN,