Dear all,
I use the SAME70 that is a 300MHz Cortex M7 device with a JLINK Debugger. I tried to use the trace facility with no success. As soon as I switch on the trace facility the startup 'hangs' in the function dbg_task_switch(). I assume it is related to the CPU core clock setting. However it is unclear to me how to do it. The device starts at 4MHz, then it get usually switched to 120MHz and finally to 300MHz. I found a note on the KEIL website saying that you should adjust the clock manually just before the clock is switched. However that is very slow and time intensive and also I the corresponding entry in the dialog box is grayed out in debug mode. So it's not possible to change it. Anyone using successfully the trace feature with the JLINK Debugger on a SAME70?
Best Regards Markus
I dig into the problem a little bit further. It seems to me it is somehow related to what happens in __main (not main() ). The startup code jumps into __main but never comes back. If I stop the execution I always hang at the line while (ITM_PORT31_U32 == 0U) in the above mentioned function. So for some reasons the debug task switch is called even before the operating system is started. If I use the prepared RTOS examples I don't have the problem - but also no output in the EventViewer.
Ends up in the Hard Fault Handler?
__main initializes the statics in RAM, assumes all memory described to the linker is up and functional, typically achieved by code in SystemInit()
It ends up in the function dbg_task_switch() that is located in the HAL_CM.c file and part of the CMSIS RTX. Any idea where this comes from?