Hardfault with Zigbee initialisation when BLE SoftDevice is included.

[anusha_14]

Hello Nordic support,

I am working on an application that works either with BLE or Zigbee and the protocol to be used is determined at application startup. Initially, my application was only Zigbee based and was using RTOS for performing various operations. This is working as expected.

Now, I have added BLE support to this application and added the necessary macros. As mentioned in this link https://infocenter.nordicsemi.com/index.jsp?topic=%2Fsdk_tz_v4.2.0%2Fzigbee_multi_examples.html (point 6), I have initialised SoftDevice by calling the function  nrf_sdh_enable_request() in main.c and then call ZB_INIT() inside an RTOS task. However, while performing Zigbee initialisation, the program goes into hardfault. 

Could you please let me know what could be the possible issue here?

Regards,

Anusha

[anusha_14]

I found that the cause for the hardfault was the execution of xQueueReceive function provided with a timeout value. If I make this timeout as 0, there is no hardfault. However, the RTOS tick does not increment. Note that RTOS tick source is coming from Systick. If I do not call nrf_sdh_enable_request(), then the RTOC tick increments. Could you please provide possible reason as to why the RTOS tick count doesn't increase when I call nrf_sdh_enable_request()? 

[Susheel Nuguru]

I am not sure, never tested systick along with BLE myself. Maybe when you enable softdevice it disables systick and clocks RTC instead? Can you check if the internal Systick counters are ticking just to check if it is still being enabled and clocked after softdevice is enabled.

[anusha_14]

Hi Susheel,

I checked if the function xPortSysTickHandler  in  port_cmsis_systick.c which increments the tick count is called when softdevice is enabled. I noticed that this function is executed only if softdevice is not enabled.

[Susheel Nuguru]

Check if the SysTick_IRQn is still enabled after the softdevice is enabled? I have a feeling that maybe the systick interrupt is being disabled after the softdevice.. You can use NVIC_GetEnableIRQ API to querry if a particular irq is enabled or not. Check if the interrupt is still enabled after the softdevice is enabled. If you find it disabled, then enable it after the softdevice is enabled. I have a feeling that softdevice might be disabling systick irq when it is initializing.

[anusha_14]

Hi Susheel,

Thanks for your response. However, it looks like I cannot use NVIC_GetEnableIRQ  to check systick interrrupt is enabled or disabled as it cannot be used with negative interrupt numbers. Systick interrupt has a value of -1. 

This seems to be also mentioned here:  NVIC check if IRQ is enabled 

I have also read that instructions WFE/WFI will also cause systick timer to stop. Ref: https://devzone.nordicsemi.com/f/nordic-q-a/76759/wfi-instruction-stops-systick-timer

However, I am not using these instructions in my multiprotocol application but are these instructions called by any of the SDK file related to BLE or Zigbee when I call nrf_sdh_enable_request()?

[Susheel Nuguru]

OK, if systick is clocked only when CPU is clocked then probably you are using tickless idle in freeRTOS that calls WFI to make the chip go to sleep mode? But that does not explain why the systick stops working on when BLE is enabled. Can you disable tickless idle mode in FreeRTOS if you have enabled it and check again.

[anusha_14]

Hi Susheel,

Thanks for your response. 

I am not using tickless Idle in FreeRTOS as it's not supported when using systick as seen in port_cmsis_systick.c:

Regards,

Anusha

[Susheel Nuguru]

I am not able to reproduce this on a BLE example using FreeRTOS and systick instead of RTC with tickless disabled. Are you sure there it is this call that makes the Systick suspended? Are you sure there is no other call to any sleep function in your code. Can you please share your project so that I can test this at my end.

[anusha_14]

Hi Susheel,

Thanks for your response. 

Yes, from what I observed, calling nrf_sdh_enable_request() was causing sytick to not work anymore. 

Is it possible for you to share the modified BLE example with FreeRTOS using Systick so that I can check against my project and see what is missing or incorrect in my project?

Regarding sharing the project, I am not sure if it is possible and will need to discuss this internally. Probably, will try to share a sample project where the issue is reproducible.

Regards,

Anusha