nRF54L15 ADC acquisiton time issues

RE: nRF54L15 ADC acquisiton time issues

Einar Thorsrud — Mon, 05 May 2025 14:11:13 GMT

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.

RE: nRF54L15 ADC acquisiton time issues

JamieHartshorne — Fri, 02 May 2025 13:30:16 GMT

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

RE: nRF54L15 ADC acquisiton time issues

Einar Thorsrud — Fri, 02 May 2025 12:57:21 GMT

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>;
	};