debugging BLE uart causes reset when breakpoint set in SDK

[Craig]

I am using Keil and nrf52 dev kit to write some UART over BLE code if I set a break-point in nus_data_handler() it cause a reset to run soon after stepping though some code and the BLE radio starts advertising even though I am stepping through code.

[haakonsh]

The SoftDevice will hardfault if you halt the CPU, the hardfault handler will reset the MCU. 

I suggest you try Monitor Mode Debugging: https://github.com/NordicPlayground/j-link-monitoring-mode-debugging.

[Craig]

Can you do this with nrf52 S112 chip? I may be doing a project based on that as well but still up in the air....

This is great thanks so much!! I will try it within a few days.....

[haakonsh]

Yeah, it's a debugging feature made by ARM or Segger and it will work on any Cortex-M series CPU. 

[awneil]

haakonsh said:

it's a debugging feature made by ARM or Segger

It relies upon standard features of the ARM Cortex-M architecture but, AFAIK, Segger is the only one to have an implementation that uses it:

https://community.arm.com/developer/tools-software/tools/f/keil-forum/35230/is-monitor-mode-debug-mmd-supported-with-ulink

https://community.st.com/s/question/0D50X00009nNQQnSAO/monitor-mode-debug-mmd-

haakonsh said:

will work on any Cortex-M series CPU

Not on Cortex-M0 - so not on nRF51

[awneil]

Craig said:

nrf52 S112 chip

"S112" is the SoftDevice - it has nothing to do with the SoftDevice.

Craig said:

I may be doing a project based on that

Note that you require at least a J-Link Plus for Monitor Mode Debug:

https://www.segger.com/products/debug-probes/j-link/technology/monitor-mode-debugging/ - see the FAQs

(but the on-board J-Link on the nRF52 DKs gives you an evaluation licence for it)