ESP8266EX ADC Specification

[tekguy49]

I have read the esp8266 hardware spec on the adc. Doc gives voltage range of 0-1V, but no DNL or INL data. I have looked at a couple of IC's and see about 13Lsb's of offset... This about 1% of the dynamic range... Is this normal? Any data on noise?

[pratik]

Hello,

The ADC can be more consistent than that in producing results. If you are getting a steady offset, please subtract that off. But if you are getting inconsistent conversions of the order of 15 LSBs, the circuit design might be the cause.
Please note that the third party modules such as ESP-01 or ESP-12 may not perform very well with the internal ADC because the I/Os have been led far out on those modules, causing interference.

For obtaining the best results with the ADC:
- Use moving average of around 5 consecutive samples. The ESP8266 produces significant noise when Wi-Fi is active.
- Use modem sleep for critical conversions.
- Make sure the analog and digital power rails are separate and properly decoupled.
- If your application is powered by USB or other such external power source, use ferrite bead on the power cord.

The ADC pin is not supposed to be used for highly accurate conversions. We recommend using external serial ADC ICs for best performance.