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memory per task

Posted by Pietro on September 20, 2007
Hi all,

how much memory do I need to create and execute a new task averagely?
If I use a PIC18F452 with a 32k flash and 1536 bytes of data memory, if I set in FreeRTOSconfig.h

#define configTOTAL_HEAP_SIZE( ( size_t ) 1536 )

I can create up to 3 tasks and they work well. But no one more.

Instead, using a PIC18F6527 with a flash of 48k and data memory of 3936 bytes, and setting

#define configTOTAL_HEAP_SIZE( ( size_t ) 2048 )

I am, at the moment, using 6 tasks without problems.

Are there any relationships between tasks and their memory usage?

Thank you in advance,


RE: memory per task

Posted by Richard on September 20, 2007
Each time you create a task the scheduler allocates two blocks of memory. The first to hold the TCB - this size is fixed. The second to hold the stack of the task, this is variable and set by the parameter you pass to the xTaskCreate() function. The stack actually used by a task is dependent on how the task is implemented (number of local variables, function call depth, etc.).


RE: memory per task

Posted by Pietro on September 21, 2007
but what is the size of memory I need to held the TCB?

RE: memory per task

Posted by Dave on September 21, 2007
sizeof( tskTCB ) or sizeof( *pxCurrentTCB ) would tell you that. You don't have to allocate this memory yourself. It is done by FreeRTOS.

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