Priority for system timer (Systick)

Kernel
1

Hi,

I used FreeRTOS on cortex M4 with tickless mode. For timing RTOS I was used to using RTC insted of Systick (because of depth of sleep mode). In M4 I set priority for RTC timer using configLIBRARY_LOWEST_INTERRUPT_PRIORITY (HAL_NVIC_SetPriority(RTC_IRQn, configLIBRARY_LOWEST_INTERRUPT_PRIORITY, 0);)
OK, but now I want to use the same on cortex M0+, but there is no macro like configLIBRARY_LOWEST_INTERRUPT_PRIORITY or configLIBRARY_MAX_INTERRUPT_PRIORITY. How should I set the priority for system timer and other periphery?

I use STM32L0.
Thank you for help.

Jan.

2

On the Cortex-M0+ there is no masking of different priority levels. Either all exceptions with configurable priority are enabled or disabled. Although the interrupts can nest, if PRIMASK is set to 1 (masked) then they will not nest or pre-empt each other so it is not important.

3

Thank you. So interrupt priority for system (RTOS) timer (in my case RTC, ussualy Systick) can be the same level as priority for EXTI from buttons?

4

Yes. I think that will be be fine. The reason for the way it is done on the Cortex-M4 is to stop any interrupts which access the API from corrupting API operations in other interrupts. This is not a problem in this port unless you enable interrupts whilst in an interrupt.