Hardfault ble_nus_send_data

This looks like a POP instruction gone wrong, mostly happens when the POP instruction put garbage values in PC to return to the previous context. Hard to say what caused the stack corruption with the information you provided. Can you run your program on nRF52840 to see if this problem goes away. If it does, then we can be sure that this is caused by a stack overflow

This looks like a POP instruction gone wrong, mostly happens when the POP instruction put garbage values in PC to return to the previous context. Hard to say what caused the stack corruption with the information you provided. Can you run your program on nRF52840 to see if this problem goes away. If it does, then we can be sure that this is caused by a stack overflow

Unfortunately cant run on nrf52840 since its our own device with plenty peripherals. any other suggestions?

Im thinking to remove DFUS and may be this would provide enough memory?

with FreeRTOS you can attempt to catch a stack overflow using these two methods. They are not 100% effective but still are good ways to catch stack overflow a few times.

First try the above method to see if the RTOS can catch an overflow, if not, then please remove the modules that you do not need to reduce the stack usage of your app.

I actually had this configured to method 2 already. I tried with method 1, but no stack overflow was detected.

I just also removed DFU service, but it didnt help.

Would you have more suggestions?

Additional piece of info: Im using device as Central and Peripheral with 2 links maximum.

Can you give me the project after you disable the DFU and as minimalistic as possible to be able to try to dig a bit deeper on my desk out of my own curiosity?

Can you comment out all places where you have __WFE() instruction and let the device run in full power? 

If that helps then I can discuss the reason for that behavior and the workaround.

Tried to remove __WFE() as you suggested, no different behavior detected.

Ill try to prepare a cut down project for you to check. in the meantime if you have any ideas please let me know. Very stuck here :S