Hello everyone,
For my current project I need the FreeRTOS+MPU to work on H7. I got it somehow to work with DTCMs. However, when I try to move the complete memory allocation to the AXI SRAMs the FreeRTOS is hanging in the systick handler (there is a for(;;) there and goes out with break instructions).
After some experiments it was found that the system works if I do the following:
- Disable the DCACHE completly or
- Set an MPU region for the freeRTOS heap memory as non-cacheable (TEX = 001b, c = 0b, b = 0b)
I dont understand how I can have a cache coehrency problem since I dont have any DMAs or other processes writing into the AXI ram. The project is very very simple. It is just one thread and in the run function I have a counter incrementing.
To map the FreeRTOS to H7 I follow the steps on the following thread:
https://freertos.org/FreeRTOS_Support_Forum_Archive/May_2018/freertos_Cortex-M7_MPU_a9b4e3d5j.html
I attach the Attolic project here. in the main.h there are two compile switches. The system works if the ENABLE_DCACHE is commented or both ENABLE_DCACHE and ENABLE_NON_CACHEABLE_FREERTOS_HEAP are enabled.
I am running out of ideas what to try. Any help would be great.
I am using a Nucleo board in the project
THanks a lot,
Best regards,
Joao
