BLE connection not working with smartphone but with Dongle

[Xandberg]

Hi Nordic Team,

We are working with two nrf52840 chips that communicate with each other via gazell. To change system settings we write characteristics via BLE. Recently we noticed a weird behavior and we have not been able to fix it.

If we activate BLE on one chip (the GZLL-device in our gazell connection) and try to connect it to a smartphone the chip freezes and has to be restarted.

The interesting thing is that it only happens when connecting to smartphones (both IOS and android) but not with the BLE-dongle and PC. Furthermore it´s working on the GZLL-host despite both running the same BLE code. When flashing the GZLL-host software on the GZLL-device chip everything is fine so the problem must lie somewhere in the non-BLE code.

We tried stepping through it with our debugger but since the BLE process is so time-critical we weren't able to spot what exactly is causing the problem. However, we always ended up in: app_error_weak.c - NRF_BREAKPOINT_COND.

We suppose that there are some interrupts or timers in the background that interfere with the BLE connection.

Do you have any ideas about what might cause the problem and how we could fix it?

[Xandberg]

Disabled interrupts is a great approach that we had not tried yet. Unfortunately we never disable the interrupts and the highest priority interrupt we use is 3.

We initialize the LFCLK at startup with these settings:

NRF_CLOCK->LFCLKSRC  = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);

Later we configure the BLE stack using the default settings:

err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);

I hope these are the parameters you were asking for.

[Kenneth]

I want to know the values you have set for these 4 defines that is used in nrf_sdh_enable_request():

nrf_clock_lf_cfg_t const clock_lf_cfg =
{
.source = NRF_SDH_CLOCK_LF_SRC,
.rc_ctiv = NRF_SDH_CLOCK_LF_RC_CTIV,
.rc_temp_ctiv = NRF_SDH_CLOCK_LF_RC_TEMP_CTIV,
.accuracy = NRF_SDH_CLOCK_LF_ACCURACY
};

Kenneth

[Xandberg]

Alright in that case the values are:

#define NRF_SDH_CLOCK_LF_SRC 0

#define NRF_SDH_CLOCK_LF_RC_CTIV 16

#define NRF_SDH_CLOCK_LF_RC_TEMP_CTIV 2

#define NRF_SDH_CLOCK_LF_ACCURACY 1

However, these are the same values as in our GZLL-host in which the BLE works properly. 

[Kenneth]

Those settings look good.

If I understand your description correctly you only experience the fault shown here when debugging (e.g. stepping etc):
https://devzone.nordicsemi.com/f/nordic-q-a/75242/ble-connection-not-working-with-smartphone-but-with-dongle/310369#310369

It never go here if the code is free-running (e.g. power on reset->run without debugging). Based on that I think the above error is caused by debugger (debugger cause the softdevice timing to fail since it can no longer ensure correct timing), and the above issue is not related to your original case:

"If we activate BLE on one chip (the GZLL-device in our gazell connection) and try to connect it to a smartphone the chip freezes and has to be restarted."

Then we are not any closer to finding why your code freeze, because I don't think the above two cases are related. Instead of debugging are you able to add some RTT or UART logging so you may find where the code is stuck?

Kenneth

[Xandberg]

Yeah, you are absolutely right. We enter that specific error function only when debugging but the freezing happens in any setup. 

We have been trying to add RTT logging initially but could not find the problem. We will continue to try to find the error and reply again when we could narrow it further down.

Thanks anyways for your help so far.