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High Priority ISR

Posted by KTC on December 4, 2012
We do currently have a system that is OSless. It is state machine based but due to number of things we are adding, we like to add FreeRtos and convert our system.

One of the major limitations of our system is an ISR which we monitor something in real time. (ADC data analyzed). There are hard real time limitations and this ISR cannot be stopped, postponed etc. It currently occupies 60% of the CPU load.

I have a few questions:
- Can we run this ISR outside the context of FreeRtos and still manage to post a semaphore to a processing task? It seems Freertos wants to limit the priority of the interrupts and there is a max value.

- If above is possible, is there an example we can take a look?

RE: High Priority ISR

Posted by Richard on December 5, 2012
Some ports allow high priority interrupts to remain unaffected by the kernel (the kernel never disables them), but FreeRTOS API functions cannot be called from these interrupts.


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