Hi all, I am using FreeRTOS on a CM4F port (STM32F429ZI) with CubeMX. In this scheme, there is a timer interrupt (Cortex timer periphery, not RTOS timer), that should periodically transmit some data over SPI using interrupt. The RTOS timer cannot be used due to requirements in precision/realtime. Without FreeRTOS, it works fine, the SPI transmit function HALSPITransmit_IT() gets called from timer elapsed callback and the according TxCplt interrupt is called upon completion. However, when FreeRTOS is running, the call HALSPITransmit_IT(), called from timer elapsed callback, results in a hard fault crash. It is namely the setting of the CR register in __HALSPIENABLEIT(hspi, (SPIITRXNE | SPIIT_ERR)) that causes the crash. The mentioned interrupts do not call any FreeRTOS API functions. SPI interrupt is currently on priority 1 and the timer interrupt on priority 2 (seen from Cortex-M port, 0 = highest prio). However, having both on priority 5 (which is set as the threshold for RTOS API functions, configMAXSYSCALLINTERRUPTPRIORITY_) does not change anything in the behaviour. Without the timer and SPI interrupt, FreeRTOS works fine. Any ideas? Thanks a lot in advance. Cheers, auraner

I am using FreeRTOS on a CM4F port (STM32F429ZI) with CubeMX. In this scheme, there is a timer interrupt (Cortex timer periphery, not RTOS timer), that should periodically transmit some data over SPI using interrupt. The RTOS timer cannot be used due to requirements in precision/realtime.

When I read this, and without reading further, I think of an alternative solution of which I think it will also meet the requirements, and that will have less problems. A timer goes off, triggers an interrupt, and why don’t you wake-up a task that will send the SPI data. ~~~ volatile uint32t ulLastTimeCount; void vTimerInterrupt( ) { BaseTypet xHigherPriorityTaskWoken = pdFALSE;

/* Make sure the Timer interrupt won't be repeated. */
uint32_t ulStatus = Instance->SR;
if( ( ulStatus & TIM_FLAG_UPDATE ) != 0 )
{
    /* May be different in your case. */
    Instance->SR = ~(TIM_FLAG_UPDATE);
    ulLastTimeCount = Instance->CNT;

    /* Wake-up the task and yield. */
    if( xMyTaskHandle != NULL )
    {
        vTaskNotifyGiveFromISR( xMyTaskHandle, &xHigherPriorityTaskWoken );
        portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
    }
}

} ~~~ Alternatively, you can send a message to a task ( xQueueSendFromISR() ) which will wake it up. I don’t think that HAL_SPI_Transmit_IT() was written to be called from an interrupt context. It may work in a bare-metal application, but I would not recommend to use it in a multi-tasking system.