Read one sample from ADC without timers.

[Rafael Barrero]

I'm having trouble reading value from ADC. What I want is to read a sample and not set any timer, since I want to run it inside a timer itself and have the refreshed value. I want to read a sample and not fill a buffer because I need a value without being too precise, and that doesn't raise the consumption too much or take too long so that most of the time it can be in low consumption. I have been trying to run sample code mixing what I have found around here as what comes in the saadc example on SDKs

The example I am referring to specifically of not using timers is found here:

devzone.nordicsemi.com/.../simplest-way-to-read-an-adc-input

Best regards

[Jørgen Holmefjord]

Hi,

The thread you linked is for the ADC in nRF51 series. It differs quite a bit from the SAADC in nRF52 series.

I have created a minimal blocking SAADC example in SDK 16.0.0 that you can use for reference:

saadc_simple_blocking_sdk_16.0.0.zip

Note that the SAADC will always work in an event-driven way. The difference with blocking mode is that the function will busy loop inside the function until the sampling is done.

Best regards,
Jørgen

[Rafael Barrero]

Okay thanks, I'm trying to adapt to my code and see if works. I'm tryimg to understand your example and my biggest doubt is about "saadc_callback". Could you explain what purpose that function has?

As a complementary question, I want to use ADC throught P0.28(supposed to be Analog Input 4).. How result the code? I tried changing 

nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);

to

nrf_saadc_channel_config_t channel_config =
NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN4);

but not work.

Thank you, best regards

[Jørgen Holmefjord]

It is not possible to initialize the SAADC driver itself in blocking mode, hence a callback is required to handle the events when event-driven sampling is used. As you can see, the callback is blank and will not be called in this sample application. You could pass 'NULL' to the init function, but the driver will assert in debug mode if no callback is provided.

The change you proposed for using AIN4 is correct. I tested that this works with the code for P0.28.

[Rafael Barrero]

Ok I retried and it works. My problem after your answer was that I defined an init function but I didn't call it. Thanks for all.

Best regards