Hello. In a freeRT0S project created with Stm32cubemX (freeRTOS v. 9.0.0 CMSIS-RTOS v.1.02) my program gives a hardfault when the following line is called from my one and only task (created with priority osPriorityNormal: armcfftf32(&armcfftsRf32len2048, SampleBufferFloat, ifftFlag, doBitReverse); However, if I call the exact same function with the same parameters before the task is started then it returns normally. The call stack only shows PendSV_Handler before the hard fault. I implemented the prvGetRegistersFromStack to copy the registers, but I’m struggling to understand what I’m looking at. $pc just gives the address of the line prvGetRegistersFromStack. The project was generated with cubemx with mostly default values for freeRTOS. I have read the warning about interrupt levels and I don’t it applies here since I have only started one task and aren’t calling any freeRTOS functions from ISR. There is also some SPI DMA going on in the background, but I don’t believe the issue is related to this. If I don’t call the armcfftf32 funtion, the program appears to continue working just fine. I’d be grateful for any ideas of where to start looking. Many thanks.

So just to eliminate any other cause, I created a new Cubemx project with only freeRTOS (so no DMA etc.) and addded in the FFT function to a single task. Again, the FFT function completes normally if called outside the task (before the task is started). If called inside the task then I again get a hard fault at xPortPendSVHandler. The timebase source is TIM7 this time. Last time it was TIM1.

Starting with the basics – do you have configASSERT() defined (with the latest version of FreeRTOS, which contains many more asserts()), and do you have stack overflow detection turned on? https://www.freertos.org/Stacks-and-stack-overflow-checking.html

Hi. Yes, I have the following defined: #define configASSERT( x ) if ((x) == 0) {taskDISABLE_INTERRUPTS(); for( ;; );} #define configCHECK_FOR_STACK_OVERFLOW 1 I’m using the latest available version of CubeMX. I see that there is a v10 of freeRTOS. I will attempt to install it over the CubeMx version.

I installed the latest version. No change other than now in the call stack I have a call to vTaskSwitchContext visible below PendSV_Handler. When I go to it, it’s taskCHECKFORSTACK_OVERFLOW(); I’m not sure how to interpret this.

So I put a breakpoint in vApplicationStackOverflowHook() and I end up there. So it looks like I’ve got some stack overflow. Thanks for helping me narrow it down somewhat. I have no idea what’s causing the stack overflow, though! ~~~ __weak void vApplicationStackOverflowHook(xTaskHandle xTask, signed char pcTaskName) { / Run time stack overflow checking is performed if configCHECKFORSTACK_OVERFLOW is defined to 1 or 2. This hook function is called if a stack overflow is detected. */ asm(“bkpt 255”); } ~~~

Out of desperation I increased the configMINIMALSTACKSIZE from 128 to 2048 and I no longer get the hard fault. I’m confused, though. I thought this stack size was for the idle task which is doing nothing in my case. I wonder whether it’s just kicking the problem down the road, though.

First, set configCHECKFORSTACK_OVERFLOW to 2, not 1, it is then much more reliable. configMINIMALSTACKSIZE is only used by the kernel to dimension the size of the stack used by the Idle task, but lots of the standard demo tasks use the same constant to make them portable across multiple architectures.