FreeRTOS wants the stack and reset vectors

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FreeRTOS wants the stack and reset vectors

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pietrodicastri
Senior Contributor II

Good morning

I have been fighting to start the FreeRTOS, it appeared not working after remapping the VTOR for moving the vector table in ram.

It works if the first two entries in the vector table are copied as well, I was not doing so.

I don't see any reason for , in my understanding these two entries are used at reset and never more. 
A help to understand the reason ....

Pietro

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FreeRTOS_org
Contributor IV

Your post is contradictory - first you say you have copied the vector table, then you say you have only copied part of the vector table.  The first part of the vector table on all Cortex-M devices is always the same, and FreeRTOS uses the address of the stack, which it reads from the vector table, to ensure it minimises RAM usage when it starts the scheduler.

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pietrodicastri
Senior Contributor II

Hello Richard

Thank You for the assistance. 
Effectively the copying of the vector table was already part of the application, I always did without copying the first two, because I always thought not relevant after the boot. 
Now it is clear the reason.

I am very grateful for the answer, and for the good assistance on the FreeRTOS forum.

Thank You

Best Regards

Pietro

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FreeRTOS_org
Contributor IV

Your post is contradictory - first you say you have copied the vector table, then you say you have only copied part of the vector table.  The first part of the vector table on all Cortex-M devices is always the same, and FreeRTOS uses the address of the stack, which it reads from the vector table, to ensure it minimises RAM usage when it starts the scheduler.