Unknown function at 0x00020906

[RO]

Hello,

I'm flashing custom code onto a nRF52840 based PCB.

I'm using SDK v14.2, SES 4.52.

The board was running fine for a couple of days.

Suddenly when I reflashed to debug, I got the following error: Unknown function at 0x00020906

What might have happened suddenly?

Thanks

[Susheel Nuguru]

What might have happened suddenly?

Unknown function in debug mode does not mean any error. It means that the debugger is unable to link the instruction address to the source files. This could be caused for many reason based on how you have compiled your project. If you want to debug the project, make sure that you compile it with debug symbolic links included and with no code optimizations.

[RO]

But I can flash other boards(similar PCB) just fine, so I don't think it's a issue with the development environment. 

Any other ideas?

[Susheel Nuguru]

Similar PCB design or the same PCB design? More importantly is it the same executable running on other boards as well?

Most likely you know about this but are you using the BLE stack (Softdevice) in your device? it is not possible to view sources of the softdevice when you attempt to step into it.

Does your debugger stops when you get this error message or can you still continue to debug?