NRF52832 External LF clock

Question

Hi,

I am trying to configure the nRF52832 on my custom board to work on the 32.768KHz clock signal from the host controller. I have configured the LFCLKSRC register to use the external source and I start the LFCLK. But the clock does not seem to start.

Here is the code that I used to configure my register.

NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos)|(CLOCK_LFCLKSRC_BYPASS_Enabled << CLOCK_LFCLKSRC_BYPASS_Pos ) |
 (CLOCK_LFCLKSRC_EXTERNAL_Enabled << CLOCK_LFCLKSRC_EXTERNAL_Pos);

NRF_CLOCK->EVENTS_LFCLKSTARTED = 0; 
NRF_CLOCK->TASKS_LFCLKSTART = 1;
while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
{//do nothing
}

The code hangs in the while loop forever. If I comment the while loop out, the code hangs in softdevice setup.

#define NRF_CLOCK_LFCLKSRC {.source = NRF_CLOCK_LF_SRC_XTAL, \
 .rc_ctiv = 0, \
 .rc_temp_ctiv = 0, \
 .xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM};

This is the clock configuration I use for the softdevice setup. If I use the RC oscillator or the SYNTH source, everything works error free. 
Also my host controller works on its own without any problems. The clock line is connected to XL1 and XL2 is grounded. 

What could be the cause of this error? I suspect that the SNR of the clock is poor causing this problem. Is that possible?

KPK · Accepted Answer

The problem was in the host processor side. The clock output was not enabled in the host and so the LFCLK could not start in the nRF52832. 
 It works once the host clock output was enabled.

NRF52832 External LF clock

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