ADC non linearity workaround

[davdav]

Hi everybody,

I use analog pin on ESP32 WROOM32 module and I am aware of ADC problem(non-linearity and reference voltage varying chip-to-chip).

In order to workaround we have place on our product and LM4040 connected to a GPIO pad in order to measure the reference voltage of ADC without routing it to a GPIO.
In practice we read the LM4040 voltage and we could calculate what is the internal reference VREF (even if it is not constant chip-to-chip) and use it in "esp_adc_cal_get_characteristics" function to correct the non-linearity.

Do you think it could be a feasible solution (waiting for the fix of espressif which it is claimed to be available for June 2018)?

Thanks you!!