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Custom IRQ handler not working with FreeRTOS

Posted by Thomas Johansen on February 17, 2011

Im using a bootloader to boot the FreeRTOS with. Therefore I cannot use the LDR PC, [PC, #-0x0120] from the startup.s file, because that is relative to the program counter (PC). The reason is that the application will be compiled to 0x5100 and VicVectAddr can not be addressed with an offset relative to PC (since vector originally located at 0x18
is now at 0x5118 in the application downloaded by the bootloader).

I have therefore written my own IRQ handler to get the correct adress from VivVector

IRQ handler:

void IRQ_Handler (void) __irq
void (*interrupt_function)();
unsigned int vector;
VICVectAddr = 0;

I then use this in my Startup.s file instead:



IRQ_Addr DCD IRQ_Handler

But for testing I haven't build the application with any flash offset. Just to test the IRQ handler

But doing this doesn't work. If I set a breakpoint in the IRQ_Handler the correct ISR is called. But after that one IRQ FreeRTOS crashes and CPU is in Undefined exception.

So my question:

Is this not possible with FreeRTOS or have I done something wrong?

Cannot se way this crashes FreeRTOS.

Using LPS2478 and FreeRTOS 5.1.2


RE: Custom IRQ handler not working with FreeRTOS

Posted by Richard on February 17, 2011
I believe richard_daemon has gone to some length to look up how to do this for you in post 4 of the following thread:


If you want to perform a context switch from an ISR (which the SWI ISR *must* do) then you need to following the instructions for writing ISR function that are on the documentation page for the port you are using - and also demonstrated in the demo projects that are provided for the port you are using.


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