Hello we would like to use FreeRtos on a M33 (STM32L5). For our projects we would like to use the following settings for the priorities: NVIC_SetPriorityGrouping(4); → 8 Groups with 32 Subpriorities bxxx.yyyy Our idea is that the groups should serve the following purpose: 0 Not used because not…

Setting all the priority bits to preempt priority makes the configuration much simpler and therefore, is still recommended for v8M ports. Consider the following example where 3 priority bits are implemented and priority group is set to 5: 000 | Priority Level 0, Sub priority Level 0 001 | Priority…

Hi Sebastian, The STM32L5 implements only three bits for interrupt priorities. And FreeRTOS requires that all three be used for preemption priorities, with no subpriorities. So, NVIC_SetPriorityGrouping(4) and configPRIO_BITS 3 and configLIBRARY_LOWEST_INTERRUPT_PRIORITY 7 are all correct for ST…

Hello Jeff, hello Hartmut, thank you very much for the quick and understandable answer. Just to be sure that we have understood it now the fixed config/interpretation ---------------------- Config 1 -------------------------------- NVIC_SetPriorityGrouping(4); // 8 Groups with 32 Subprior…

[image] jefftenney: However, a small correction for your list of interrupt priorities. The FreeRTOS interrupts (the system tick and PendSV) will use priority 7, not priority 2 …because they use configLIBRARY_LOWEST_INTERRUPT_PRIORITY if I am not mistaken. So it would be possible to set this t…

Hi Sebastian, Right – your config with NVIC_SetPriorityGrouping(4); is correct. One improvement would be to modify the comment that says with 32 Subpriorities to say with 0 subpriorities bxxx.zzzzz. Only 3 bits are implemented (the x bits) and the other 5 are unimplemented (the z bits). Your con…

Hi Oliver, That was true on the ARMv7-M ports, but the ARMv8-M ports hard-code the tick and SV ISRs to use the lowest priority. If the SV ISR ever preempts another ISR, context corruption can occur.

Thank you all for your support. We have decided to implement our project with the simple config with all preempt priority

Configure FreeRtos with Groups/Subpriorities on M33

Kernel

hs2 (Hartmut Schaefer) February 8, 2022, 4:59pm 3

I’d like to add this pretty good explanation of FreeRTOS interrupt mapping and configuration.

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Configure FreeRtos with Groups/Subpriorities on M33

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