NRF51822 sd_softdevice_enable freeze SDK 12.3 SD130 v2.0.1

[Daniel Dakhno]

My app runs the following code, that is supposed to init the SoftDevice:

nrf_clock_lf_cfg_t clock_lf_cfg = {
.source = NRF_CLOCK_LF_SRC_XTAL,
.xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM,
};

// Initialize the SoftDevice handler module.
SOFTDEVICE_HANDLER_INIT (&clock_lf_cfg, NULL);

Inside the last macro, the call to sd_softdevice_enable() freezes and never returns, nor jumps to the softdevice_fault_handler.

I have already tried executing the following code to successfully ensure that the lfck is running:

bool started = nrf_drv_clock_lfclk_is_running();

NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
NRF_CLOCK->TASKS_LFCLKSTART = 1;

while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
{
// Do nothing.
}
started = nrf_drv_clock_lfclk_is_running();

Yet, sd_softdevice_enable freezes.

Is there anything i can do to get the code up and running?

It only started to freeze on a new board, on another board it worked.

I do sadly not have any technical documentation about the current board, though...

[Vidar Berg]

Hi,

Are you sure the new board supposed to have a 32 KHz LF crystal mounted? As you may have seen from other posts, the Softdevice enable function can get stuck in a loop and never return if you select the wrong clock source or have a bad clock circuit. 

I suggest to try starting the clock manually like you did, but with the clock source set to xtal. Then see if you get the started event. 

//NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);
NRF_CLOCK->LFCLKSRC = 1; //XTAL
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
NRF_CLOCK->TASKS_LFCLKSTART = 1;

while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
{
// Do nothing.
}

[Daniel Dakhno]

You are right, that is what i initially wanted to do, but failed through brainless copy-pasting.

With the XTAL it gets stuck in the loop, indeed.

I am using this board:

although in reality it looks like this:

Is it possible that the difference between the pictures is indeed the missing Crystal?

Also, using app_timer and System on mode, are there any advantages to an external crystal?

[Vidar Berg]

Yes, it looks like it only has the footprint for a LF crystal unfortunately.  In that case you need to select the internal RC oscillator when you enable the Softdevice.

[Daniel Dakhno]

Does that have any disadvantages? How do i get app_timer to work?

[Vidar Berg]

The disadvantage is slightly increased current consumption as the Softdevice need to increase RX windows account for the lower clock tolerance and perform periodic calibration of the oscillator. But the app_timer will work as before, just not as accurate (20 ppm vs 250 ppm)

Softdevice setting to use internal RC oscillator:

    nrf_clock_lf_cfg_t clock_lf_cfg = { .source  = NRF_CLOCK_LF_SRC_RC,
                                        .rc_ctiv = 4,
                                        .rc_temp_ctiv = 1 };