RE: Adc data stability

Karl Ylvisaker — Wed, 05 Aug 2020 13:19:37 GMT

Hello,

How is your nRF52832 DK powered? Please know that the 5 V from USB is regulated to 3.3 V before being used for VDD, and the maximum VDD rating is 3.6 V if you are using the external supply.
As written in the SAADC documentation the SAADC has full scale input range, which means that the highest value it may be used to measure is VDD, which again at most can be 3.6 V.

Furthermore, the absolute maximum ratings for I/O pin voltage of the nRF52832 is 3.9 V. You therefore should not expose the I/O pins to anything higher than this, as it may permanently damage your device.

If you would like help debugging your program it would be greatly helpful if you could provide code snippets and output logs ( if any ), along with a description of the things Awneil is asking about.
To get more accurate readings you should always perform a calibration of the SAADC before usage, and in the case of large temperature change since last calibration.

Please do not hesitate to let me know if you should have any other questions, or if something still should be unclear!

Best regards,
Karl

RE: Adc data stability

pavan_142297 — Wed, 05 Aug 2020 10:55:23 GMT

I connected 5v pin of NRF devkit to analog pin. In the beginning, i got data between 538 to 540 and after some time it's increased to 565 to570.

RE: Adc data stability

awneil — Wed, 05 Aug 2020 08:04:54 GMT

[quote userid="91353" url="~/f/nordic-q-a/64514/adc-data-stability"]in example code, i am getting alternate values on fixed voltage[/quote]

What, exactly, do you mean by that?

How, exactly, did you observe this ?

How do you know that the "fixed voltage" really is constant?