What changes are needed in SDK V15 sdk_config.h so nRF52832 can run on internal RC oscillator

[Renix]

What changes are needed in SDK V15 sdk_config.h so nRF52832 can run on internal RC oscillator?

I am using the BLE UART example, nRF52832 with Soft device s132_nrf52_6.0.0, nRF5_SDK_15.0.0_a53641a

Any help appreciated

[bjorn-spockeli]

Hi Gerhard,

The BLE stack can use either an external crystal or the internal RC oscilator as the LF clock source. In case of the latter the SoftDevice will periodically calibrate it to be within the frequency tolerance stated in the BLE specification. 

you need to perform the following changes under the SoftDevice clock configuration in sdk_config in order for the nRF52832 to use the internal RC in SDK 15.0.0

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

// <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

Best regards

Bjørn