RE: NRF52840 external 32.768kHz crystal

Daniel Reisfeld — Thu, 23 Aug 2018 07:47:51 GMT

Bjorn thanks! Daniel

RE: NRF52840 external 32.768kHz crystal

bjorn-spockeli — Thu, 23 Aug 2018 07:27:36 GMT

HI Daniel,

all the examples in the SDK uses the external 32kHz crystal as the low frequency clock source by default. The LFCLK source is set in the sdk_config.h file in the examples, see below snippet

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

// <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 1
#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 0
#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 7
#endif

Best regards

Bjørn