Kinetis MicrocontrollersのトピックHow to set Interrupt priorities in CortexM0 plus (KEA-128)?

How to set Interrupt priorities in CortexM0 plus (KEA-128)?

vigneshbalaji — Wed, 26 Oct 2016 18:51:43 GMT

Hi,

I want to Change the Interrupt priority of KEA-128? Can you tell me How to do it ???

I got to know from datasheet that I have to write a value to NVIC_IPR2 register but how and what value to be written is not clearly given ???

Can you Explain this with an uart interrupt as an example and say how to write and which registers to write for it???

Re: How to set Interrupt priorities in CortexM0 plus (KEA-128)?

BlackNight — Thu, 27 Oct 2016 05:26:33 GMT

Hi Vignesh,

I suggest that you are using the CMSIS API to set the interrupt priorities, the API is

void NVIC_SetPriority(IRQn_Type IRQn, uint32_t priority);

If you are not familiar with the ARM NVIC and interrupt system and API, I recommend you have a look e.g. at https://mcuoneclipse.com/2016/08/14/arm-cortex-m-interrupts-and-freertos-part-1/

I hope this helps,

Erich

Re: How to set Interrupt priorities in CortexM0 plus (KEA-128)?

egoodii — Fri, 28 Oct 2016 12:59:25 GMT

One thing to note about the CMSIS API is that it doesn't make it 'obvious' what the 'range' of priority values needs to be. You will find that for these M0-core devices you have 0,1,2 and 3 to work with -- lower numbers, higher priority. That is, the API 'shifts' the supplied priority into the available 'upper bits' of the NVIC architecture:

SCB->SHP[_SHP_IDX(IRQn)] = ((uint32_t)(SCB->SHP[_SHP_IDX(IRQn)] & ~(0xFFUL << _BIT_SHIFT(IRQn))) |
(((priority << (8U - __NVIC_PRIO_BITS)) & (uint32_t)0xFFUL) << _BIT_SHIFT(IRQn)));