How to configure the adc periheral in the Device Tree file *.dts

[Learner]

Hello,

I am trying to figure out a way to configure the adc node using the .dts Device Tree file in a similar way to what is done for other nodes such as &spi and &i2c.

Unfortunately, all the examples I have seen so far only set the status property for the adc node. I would like to add GPIO pin numbers, resolution, etc ...

Any suggestions?

&adc {
status = "okay";
};

&spi1 {
compatible = "nordic,nrf-spim";
status = "okay";
sck-pin = <13>;
mosi-pin = <09>;
miso-pin = <40>;
};

Thank you.

[Martin Lesund]

Hi learner,

In the NCS tutorial you can see how to add a ADC peripheral to your project.

For the .dts you could use "io-channels" as shown here.

Also here is a simple unofficial ADC sample that may be of help.

[Learner]

Hi Martin,

Thank you for your answer. I did go through the Tutorial Part 2 where the ADC is NOT configured  via the .dts file. So, the idea of using io-channels in the .dts file is what I am interested in. I have read some of it and I am not sure I get it. So, I am going to have a go at changing the sample of the light intensity controller in Tutorial 2 and use the .dts file and see if I can get it to work. I will probably need your help at some point to get it to work.

Thank you for your support.

[Martin Lesund]

Hi Learner,

Sounds good. Please let me know how it goes, or if you have some additional questions that come up.

[Learner]

Hi Martin,

In NCS Tutorial Part 2- the light intensity controller, there is this section of #defines for the ADC.

/*ADC definitions and includes*/
#include <hal/nrf_saadc.h>
#define ADC_DEVICE_NAME DT_LABEL(DT_INST(0, nordic_nrf_saadc))
#define ADC_RESOLUTION 10
#define ADC_GAIN ADC_GAIN_1_6
#define ADC_REFERENCE ADC_REF_INTERNAL
#define ADC_ACQUISITION_TIME ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 10)
#define ADC_1ST_CHANNEL_ID                     0
#define ADC_1ST_CHANNEL_INPUT              NRF_SAADC_INPUT_AIN0

Since I am configuring the adc channels using the .overlay with io-channels as you suggested file as follows,

adc0: adc@4000E000 {
       label = "ADC_0";
};

n: node {
       io-channels = <&adc0 4>;
       io-channel-names = "AIN_0"";
};

I think these two lines are not needed anymore, am I right?

#define ADC_1ST_CHANNEL_ID                    0
#define ADC_1ST_CHANNEL_INPUT             NRF_SAADC_INPUT_AIN0

But I am not sure how the information in the .overlay file will get used by the C code. 

Could you please advise on what changes I need to make to the C code to make it use the new info in the overlay file.

Thank you.

[Learner]

I have assumed that the number 4 in the line below is the pin number P0.04 which corresponds to adc channel AIN0. Is this right?

io-channels = <&adc0 4>;

[Martin Lesund]

Hi Learner,
Yes, that should be correct.
p0.04 of the nRF5340, so AIN1

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf5340_pdk%2FUG%2Fnrf5340_PDK%2Fhw_analog_pins.html 

[Learner]

Hi Martin,

According to the PCA10095 schematics of the nRF5340 PDK  (nRF5340-QKAA) pin 4 on P0.04 is AIN0 not AIN1.

Could you please double check. Thank you.

Kind regards

Mohamed