Question about SAADC measurement result

RE: Question about SAADC measurement result

SeanOY — Fri, 18 Dec 2020 04:00:10 GMT

Hi Karl,

Thanks!

I use multimeter to measure the voltage of VDD, it's about 2.98V. I get it now :)

Best regards,

Sean

RE: Question about SAADC measurement result

Karl Ylvisaker — Thu, 17 Dec 2020 09:51:30 GMT

Hello Sean,

[quote user="SeanOY"]Sorry for the inadequate description.[/quote]

No problem at all.
Thank you for elaborating, this is very helpful!

[quote user="SeanOY"]4. Result of measuring GND's voltage.[/quote]

I think these measurements of GND look reasonable.
You must expect a few LSB of noise on the SAADC's output, you can read more about that in this reply by my colleague Carsten.

[quote user="SeanOY"]Result of measuring VDD's voltage.[/quote]

The nRF52833 DK regulates the 5 V supply down to 3 V, please see the DK's power section for more information about this. The unmodified SAADC peripheral example is configured to support a voltage range of 0 - 3.6 V, so your measurements of 855 of the 1024 resolution translates to 3.01 V, which is as expected. The SAADC's input range is determined by the formulas from the SAADC peripheral documentation, you may configure this to match the requirements of your application.

Please do not hesitate to ask if any part of my answer should be unclear, or if you should have any other questions! 🙂

Best regards,
Karl

RE: Question about SAADC measurement result

SeanOY — Thu, 17 Dec 2020 07:02:55 GMT

Hi Karl,

Sorry for the inadequate description.

1. Yes, I run the default demo of saadc and connect P0.02(AIN0) with gnd/vdd. The reason i test them is i want to know the upper and lower limit value of adc. My nRF5 SDK version is 17.

2. I use DK PCA10100(nRF52833).

3. The power source is USB of computer.

4. Result of measuring GND's voltage.

Result of measuring VDD's voltage.

Thanks!

Best regards,

Sean

RE: Question about SAADC measurement result

Karl Ylvisaker — Wed, 16 Dec 2020 12:40:38 GMT

Hello Sean,

[quote user=""]I want to use saadc to measure the battery's voltage, but the result I get is incorrect. [/quote][quote user=""]So I use the saadc demo of the nrf5_sdk17, then I measure GND(negative result) and VDD(less than 853). Why VDD's adc result is not 1023?[/quote]

Did you run the unmodified example? If so, please elaborate what you did in order to measure GND and VDD. Are you using a DK, or a custom board? What power source are you using?
Please also specify which connections you made, and what exact numbers you were seeing when you measured the different voltages.

If you made any modifications to the example, such as changing the SAADC or channel configurations, please elaborate on these as well.

Looking forward to resolve this issue together,

Best regards,
Karl