RE: NRF52833 SAADC incorrectly measures NRF_SAADC_INPUT_VDD channel when supply voltage is set below 3.0v

haakonsh — Wed, 26 Jan 2022 12:30:27 GMT

No apologies needed, mistakes are part of the job :)

RE: NRF52833 SAADC incorrectly measures NRF_SAADC_INPUT_VDD channel when supply voltage is set below 3.0v

2gav — Tue, 25 Jan 2022 15:08:19 GMT

Okay, I checked everything myself. I apologize, it was my mistake. A voltage higher than 3.8v is applied to one pin of the processor. Obviously this leads to problems related to the internal reference voltage of the ADC.

Since I checked the operation of the UICR register at the same time, I can say that setting the voltage through the REGOUT0 register works perfectly.

Thank you very much and once again I apologize for my mistake.

RE: NRF52833 SAADC incorrectly measures NRF_SAADC_INPUT_VDD channel when supply voltage is set below 3.0v

haakonsh — Tue, 25 Jan 2022 13:26:38 GMT

I've yet to replicate the problem, but I did think of something that we need to verify, and that is the actual voltage on the VDD rail. Do you have a multimeter that you can check VDD in the different settings in UICR?

I ask because I think it's more likely an issue with the VDD rail than the SAADC.

RE: NRF52833 SAADC incorrectly measures NRF_SAADC_INPUT_VDD channel when supply voltage is set below 3.0v

2gav — Tue, 25 Jan 2022 06:03:52 GMT

Of course, only I cannot do it qualitatively for 2.1v. Only up to 2.4v.

This is for 3.0v:

<info> app: VDD: 3000 mv; ADC RESOLUTION: 10 bits
<info> app: SAADC HAL simple example started.
<info> app: ADC event number: 0
<info> app: ADC=860 (3023 mV)
<info> app: ADC=861 (3027 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC=857 (3013 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC event number: 1
<info> app: ADC=861 (3027 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC=861 (3027 mV)
<info> app: ADC=858 (3016 mV)
<info> app: ADC event number: 2
<info> app: ADC=858 (3016 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC=861 (3027 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC event number: 3
<info> app: ADC=859 (3020 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC=859 (3020 mV)
<info> app: ADC event number: 4
<info> app: ADC=858 (3016 mV)
<info> app: ADC=861 (3027 mV)
<info> app: ADC=857 (3013 mV)
<info> app: ADC=860 (3023 mV)
<info> app: ADC=857 (3013 mV)

This is for 2.7v:

<info> app: VDD: 2700 mv; ADC RESOLUTION: 10 bits
<info> app: SAADC HAL simple example started.
<info> app: ADC event number: 0
<info> app: ADC=562 (1976 mV)
<info> app: ADC=565 (1986 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC event number: 1
<info> app: ADC=562 (1976 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC event number: 2
<info> app: ADC=563 (1979 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC event number: 3
<info> app: ADC=562 (1976 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=563 (1979 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=562 (1976 mV)
<info> app: ADC event number: 4
<info> app: ADC=563 (1979 mV)
<info> app: ADC=562 (1976 mV)
<info> app: ADC=564 (1983 mV)
<info> app: ADC=562 (1976 mV)
<info> app: ADC=565 (1986 mV)

This is for 2.4v:

<info> app: VDD: 2400 mv; ADC RESOLUTION: 10 bits
<info> app: SAADC HAL simple example started.
<info> app: ADC event number: 0
<info> app: ADC=516 (1814 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=515 (1811 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC event number: 1
<info> app: ADC=516 (1814 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC event number: 2
<info> app: ADC=515 (1811 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=515 (1811 mV)
<info> app: ADC event number: 3
<info> app: ADC=516 (1814 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=515 (1811 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC event number: 4
<info> app: ADC=514 (1807 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=517 (1818 mV)
<info> app: ADC=516 (1814 mV)
<info> app: ADC=516 (1814 mV)

If my data is not confirmed with you, then this is very good. So the problem is somewhere in my device. And I apologize in advance for the panic.

Thank you, very very much.

RE: NRF52833 SAADC incorrectly measures NRF_SAADC_INPUT_VDD channel when supply voltage is set below 3.0v

haakonsh — Mon, 24 Jan 2022 14:42:12 GMT

I'll try to replicated the issue on my end.

Can you share a couple of ADC values at UICR_REGOUT0_VOUT_3V0 and UICR_REGOUT0_VOUT_2V1 ?