RE: Question about the nRF Connect SDK v2.1.0 - adc example using nRF52840(PCA10056)

Simon — Thu, 20 Oct 2022 11:49:28 GMT

[quote user=""]My first question is: What is the difference between the `arduino_adc` vs the `zephyr_user` ADC? [/quote]

The VS Code Extension gives a good description of "zephyr,user":

The zephyr,user node does not have a compatible field. This is unusual, as far as I'm aware, a node will always have a compatible field. The compatible field can then be used to access the DTS node properties from a .c/.h file

The arduino_adc on the other hand has a compatible field, which is "arduino,uno-adc". I could not find any samples in the nRF Connect SDK that used this node. Check out the arduino,uno-adc binding for an explanation of this compatible: https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1/dts/bindings/adc/arduino%2Cuno-adc.yaml

[quote user=""]The second question: Based on the PCA10056 pin assignment, AIN0 - AIN7 are analog input pins, if I would like to use pins other than 0, 1, and 7. How can I initialize the DT?[/quote]

You can not use any other pins than AIN0-AIN7. Check out nRF52840 --> Pin assignments to see what Pin number that are associated with AIN0-AIN7:

AIN0	P0.04
AIN1	P0.05
AIN2	P0.06
AIN3	P0.07
AIN4	P0.25
AIN5	P0.26
AIN6	P0.27
AIN7	P0.28

I would recommend you to read through nRF52840 --> SAADC (ADC), to get a better understanding of the ADC on a deeper level

If you would like to use P0.28 for example, you can modify the file \zephyr\samples\drivers\adc\boards\nrf52840dk_nrf52840.overlay accordingly:

/ {
	zephyr,user {
		io-channels = <&adc 7>;
	};
};

You may take a look at 3.5 Add the ADC peripheral as well, NCS 1.5.0 is used which is a bit outdated, but the section should still be useful.

[quote user=""]

The third question: Can anyone helps me understand the following properties in the node?

zephyr,gain;

zephyr,reference;

zephyr,vref-mv;

zephyr,acquisition-time;

zephyr,input-positive;

zephyr,input-negative;

zephyr,resolution;

[/quote]

These fields belongs to the compatible "nordic,nrf-saadc". Take a look at the associated bindings for more information:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1/dts/bindings/adc/nordic%2Cnrf-saadc.yaml,

this includes the binding adc-controller.yaml, which contains a description for all these fields

https://github.com/nrfconnect/sdk-zephyr/blob/v3.1.99-ncs1/dts/bindings/adc/adc-controller.yaml

For an even more thorough description of these fields, check out

nRF52840 --> SAADC

Best regards,

Simon

RE: Question about the nRF Connect SDK v2.1.0 - adc example using nRF52840(PCA10056)

Simon — Wed, 19 Oct 2022 13:23:51 GMT

Hello,

I'll take a look at your question later today/tomorrow

Best regards,

Simon