RE: Enable bypass of LFCLK crystal oscillator with external clock source

Sigurd — Wed, 29 Apr 2020 14:24:55 GMT

Hi,

The SoftDevice can be configured to use one of two available LFCLK sources: the internal RC Oscillator, or external Crystal Oscillator. In both cases BYPASS and EXTERNAL is set to 0.

There is no SoftDevice API or sdk_config.h settings for BYPASS or EXTERNAL. But, there is a workaround for this, and that is by starting the LFCLK before you enable the SoftDevice.

NRF_CLOCK->LFCLKSRC = my_settings;

NRF_CLOCK->TASKS_LFCLKSTART = 1;
while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);

You can keep the softdevice configuration as-is (ie: SRC_XTAL and so-forth).

If you hang in the while-loop when debugging, it might point to issues with the external oscillator connection.