Unknown function at <address> starts executing during the ISR's execution</address>

[morpho]

So...I have an idle task running then a UART interrupt fires upon a character being sent over the serial, and somewhere during the execution of the ISR, it attempts to execute an "unknown" function as shown in the call stack here

And here's the corresponding ASM code which I have no idea about cause I can't trace it.

Pressing the execute debugger button still executes the same function 0x774. Is it in sleep mode?

[Einar Thorsrud]

Hi,

This is within the MBR. The MBR forwards interrupts to the SoftDevice, which forwards them to your application. I am not sure what you mean by sleep mode? (If the CPU is executing code, it is not in sleep at that instant).

[morpho]

What's exactly MBR? Why is it getting "stuck" on here then once the interrupt is fired?

[Einar Thorsrud]

Hi,

The MBR is the master boot record. It is the first page of the SoftDevice. Execution should not get "stuck there". How did you end up here when debugging? As interrupts are forwarded by the SoftDevice I wonder if it could be simply that you are stepping through code execution also when it is outside your application binary, but that is just a guess.

[morpho]

Can you confirm if the scheduler wipes out the stuff allocated on the stack inside main once it runs?

[Einar Thorsrud]

Looking at your screenshot I assume you refer to the FreeRTOS scheduler. The stack will not be explicitly wiped out, no. However I believe the main stack is used for ISRs etc, so part of the data will be overwritten at some point.