nRF54L15 ADC acquisiton time issues

[JamieHartshorne]

Hi, I am trying to set my acqtime different to the max value. And the build throws an error unless i set it to ACQTIME_MAX.

It appears in the header file it needs some other values that i dont seem to have defined? How could i get this working for the NRF54L15, i am working on porting the project from the nrf52840dk to this board. I am using the 3.0.1 SDK. My guess is im missing some sort of definition somewhere but I can't seem to find where. The header file wants values for variables in the form of SAADC_CH_CONFIG_TACQ_5us etc.

    channel.channel_config.gain = NRF_SAADC_GAIN1_4;

    channel.channel_config.acq_time =   NRF_SAADC_ACQTIME_5US;

[Einar Thorsrud]

Hi,

Can you share more about how you use the SAADC? If you refer to the this ADC sample, you can modify the configuration slightly to use GAIN 1/4 and 5 us acquisition time, and that works when I test on my end with these changes to channel 0 modified like this in the overlay file:

	channel@0 {
		reg = <0>;
		zephyr,gain = "ADC_GAIN_1_4";
		zephyr,reference = "ADC_REF_INTERNAL";
		zephyr,acquisition-time = <ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 5)>;
		zephyr,input-positive = <NRF_SAADC_AIN4>; /* P1.11 */
		zephyr,resolution = <10>;
	};

[JamieHartshorne]

https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/lessons/lesson-6-analog-to-digital-converter-adc/topic/exercise-3-interfacing-with-adc-using-nrfx-drivers-and-timer-ppi/

hi Einar, I am essentially following this guide. I am using the nrfx drivers

    /* STEP 4.7 - Change gain config and set acquisition time in default config and apply channel configuration */

    channel.channel_config.gain = NRF_SAADC_GAIN1_4;

    channel.channel_config.acq_time =   NRF_SAADC_ACQTIME_MAX;

    err = nrfx_saadc_channels_config(&channel, 1);

    if (err != NRFX_SUCCESS) {

        //LOG_ERR("nrfx_saadc_channels_config error: %08x", err);

        return;

    }

i just ended up replacing acqtime with the number 5 and it worked for a 5us sample rate so i guess thats fixed it. although its odd the enum doesnt work anymore

[Einar Thorsrud]

Hi,

I see. Yes, the nRF54L has a much higher granularity with regard to acquisition time (see datsheet), and it makes less sense to use enums in that case. Therefore, the nrfx API had to change to acomodate this, so the enums are not used for nRF54L.