Another SoftDevice LFCLOCK issue, this time on nRF52840

Question

We are developing with the nRF52840, in this instance present in a Laird BL654 module carried by their DVK-BL654 dev board. 
 After trying three separate examples that attempt to use SoftDevice, they all seem to lock up in the SoftDevice code, waiting for the LFCLOCK to start. 
 The dev board doesn't enable the 32.768Xtal by default, so I've attempted to work around this by selecting the other LF sources, however in each instance I get the same behaviour. 
 I'm not aware of a specific BSP for Laird's module or board, however it seems to strongly resemble the PCA10056, but with a built in segger. 
 I've tried non SoftDevice example code with the same board, so far without problems.

bjorn-spockeli · Accepted Answer

Hi Rob,

Which SDK and SoftDevice version are you using?

All SoftDevices for the nRF52840 support both 32kHx XTAL and the use of the internal 32kHz RC oscillator

You should only have to set the following defines in sdk_config.h for the nRF52840 to use the RC oscillator instead of the XTAL

// </h> 
//==========================================================

// <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 16
#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 2
#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

// </h> 
//==========================================================

Best regards

Bjørn

Another SoftDevice LFCLOCK issue, this time on nRF52840

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