RE: 32.768KHz RC Oscillator Configuration for BLE central

JONATHAN LL — Thu, 02 Oct 2025 11:21:42 GMT

Hi,

Can you create a new ticket here, sharing info on your setup, what SDK version, hardware and so on, and you can link to this case for relevance.

Regards,
Jonathan

RE: 32.768KHz RC Oscillator Configuration for BLE central

Aayushikanojiya — Wed, 01 Oct 2025 18:10:16 GMT

Hello I am using custom nrf_ble_app_c central example on ISC-nrf52832-A which uses internal RC oscillator and I have done the configuration in sdk_config.h file for the RC oscillator selection

// <h> Clock - SoftDevice clock configuration

//==========================================================

// <o> NRF_SDH_CLOCK_LF_SRC - SoftDevice clock source.

// <0=> NRF_CLOCK_LF_SRC_RC

// <1=> NRF_CLOCK_LF_SRC_XTAL

// <2=> NRF_CLOCK_LF_SRC_SYNTH

#ifndef NRF_SDH_CLOCK_LF_SRC

#define NRF_SDH_CLOCK_LF_SRC 0

#endif

// <o> NRF_SDH_CLOCK_LF_RC_CTIV - SoftDevice calibration timer interval.

#ifndef NRF_SDH_CLOCK_LF_RC_CTIV

#define NRF_SDH_CLOCK_LF_RC_CTIV 1

#endif

// <o> NRF_SDH_CLOCK_LF_RC_TEMP_CTIV - SoftDevice calibration timer interval under constant temperature.

// <i> How often (in number of calibration intervals) the RC oscillator shall be calibrated

// <i> if the temperature has not changed.

#ifndef NRF_SDH_CLOCK_LF_RC_TEMP_CTIV

#define NRF_SDH_CLOCK_LF_RC_TEMP_CTIV 0

#endif

// <o> NRF_SDH_CLOCK_LF_ACCURACY - External clock accuracy used in the LL to compute timing.

// <0=> NRF_CLOCK_LF_ACCURACY_250_PPM

// <1=> NRF_CLOCK_LF_ACCURACY_500_PPM

// <2=> NRF_CLOCK_LF_ACCURACY_150_PPM

// <3=> NRF_CLOCK_LF_ACCURACY_100_PPM

// <4=> NRF_CLOCK_LF_ACCURACY_75_PPM

// <5=> NRF_CLOCK_LF_ACCURACY_50_PPM

// <6=> NRF_CLOCK_LF_ACCURACY_30_PPM

// <7=> NRF_CLOCK_LF_ACCURACY_20_PPM

// <8=> NRF_CLOCK_LF_ACCURACY_10_PPM

// <9=> NRF_CLOCK_LF_ACCURACY_5_PPM

// <10=> NRF_CLOCK_LF_ACCURACY_2_PPM

// <11=> NRF_CLOCK_LF_ACCURACY_1_PPM

#ifndef NRF_SDH_CLOCK_LF_ACCURACY

#define NRF_SDH_CLOCK_LF_ACCURACY 1

#endif

but the same is not working for me , please guide me

RE: 32.768KHz RC Oscillator Configuration for BLE central

ovrebekk — Tue, 13 Mar 2018 13:27:33 GMT

You can't guarantee better accuracy than 250ppm from the RC in the nRF51 series, but in general the more often you calibrate the more accurate it will be (at the cost of higher power consumption, as you say).

The most aggressive settings you can use is rc_ctiv=1 and rx_temp_ctiv=0. Then the RC will be calibrated every 250ms, even if the temperature is stable.

Best regards
Torbjørn