Including libraries for ADC usage

[EntroP]

Hello, I am trying to develop an application using the ADC of the nrf52832. For this, I have included the "nrfx_adc.h" library into my main code. When I try compiling the project though, I get loads of errors saying that basically every variable in the "nrf_adc.h" library (which is referenced in "nrfx_adc.h") is undefined. For reference, I tried looking up the "nrf_saadc.h" library and wanted to know where those definitions are, and apparently they are in a library called "nrf52_bitfields.h". But there's none for the variables in "nrf_adc.h"!

Are they in a different file and I am just not finding them? Can I simply use the "nrfx_saadc.h" library? I've checked the main file of the ADC sample application and there seems to be some extra methods so I don't know how much of those methods I would actually need to copy into my program?

Help would be much appreciated, thanks in advance.

[Simon]

Have you included the header files correctly? See this link. Also remember to include the .c files, and enable the features needed for ADC in the sdk_config file, as specified in the answer above. However, when enabling the features in the sdk_config.h file, there are two different kind of definitions: The old kind (SAADC_ENABLED) and the new NRFX kind (NRFX_SAADC_ENABLED). Look at this link for a guide on how to do it correctly.

Best regards, Simon.

[EntroP]

I am pretty sure I did include the header files correctly, since I don't get the "No such file or directory" error. In fact, I just tested doing it manually and it doesn't resolve the issue. Same for the other advice.

The error doesn't occur when the file is included, but afterwards. I added a screenshot to make this more clear.

When I check out the saadc example, those definitions (like "SAADC_INTENSET_END_Msk") for example are in the nrf52_bitfields.h, while "ADC_INTENSET_END_Msk" and the other definitions used in nrf_adc.h are not. Where can I find those?

[Simon]

The difference between the SAADC driver and the ADC driver, is that the former is intended to use for the nRF52 series while the latter originates from the nRF51 series. Also, as mentioned here, SAADC has direct memory access and can move its samples into RAM without using the CPU. The reason nrf_adc.h is still included in SDK 15 is for backwards compatibility. 

I would recommend you to implement ADC using the SAADC driver. Using the SAADC Example as a reference might help you with that.

Please ask if you encounter any problems while doing this.

Best regards, Simon

[EntroP]

Thank you, I already guessed that this would be the way to go. However, when trying to include the "nrf_drv_saadc.h" file, I get the following errors:

But when I include "nrfx_saadc.h" directly, the errors disappear! What's up with that?

[Simon]

Have you been able to work this out?

[EntroP]

Yep, I didn't realize that the "nrf_drv_xxxxx" drivers are the outdated ones at first. Simply replacing them all with the equivalent "nrfx_xxxxx" drivers resolved my issue.

I have one question regarding the "nrfx_clock" driver though: Do I have to define a proper event handler for the parameter, or can I simply give it an empty one (not NULL obviously, but one that doesn't do anything)?

[Simon]

That is true, the nrx drivers are used in the newer SDK's, but you can still use the old functions, if you add the legacy layer for the driver.

Do you need the clock driver for the ADC? The SAADC Example uses the timer driver (which runs on the high-frequency clock) along with PPI to trigger a sample task.

[EntroP]

Well, I used the "serial" example as the base for my project and added the libraries and code from the "SAADC" example. Since the serial example works with some legacy libraries, I decided to replace those with the new ones, which worked fine, except in this one case where the "nrfx_clock_init" method needs to be given an event handler while the old "nrf_drv_clock_init" doesn't.

So I'm wondering how to go about this event handler, since the serial code doesn't work anymore now.

[Simon]

You must provide a event handler for nrfx_clock_init(..), as mentioned in the comment for the function in nrfx_clock.h:

"Event handler provided by the user, Must not be NULL."

If you choose to use the old functions along with the glue layer (nrf_drv_clock.c/h), this will be fixed for you "behind the scenes". However if you choose to use the nrfx functions, you should look inside nrf_drv_clock.c of how to use nrfx_clock_init(..).