Nuvoton M453: FreeRTOS interrupt stops all tasks

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1

Hi all,

I am using nuvoton M453 mcu with freeRTOS and currently I am stuck in my code that I create 3 tasks; all are running on same priority which works fine but when I want to run 2 tasks from H/W interrupt (a button). All tasks stop working.I also checked the MAX_PRIORTES and MAX_SYSCALL_INTERRUPT_PRIORITY which seems to be ok.I am new in RTOS code so, can anyone share me some example code having tasks call from interrupt and then tasks working after interrupt.

2

You can wait for a notification in your task and your ISR can send the task notification. The following page contains one such example - RTOS Task Notifications - FreeRTOSā„¢.

3

Hello @Rajput, welcome to the FreeRTOS community!

Adding to @aggargā€™s response, hereā€™s an example approach for your application using task notifications (one of FreeRTOSā€™s preferred ways to communicate from an ISR) to ā€œwakeā€ two tasks (Task1 and Task2) when a button interrupt occurs. Make sure that the interrupt is set with a priority at or below configMAX_SYSCALL_INTERRUPT_PRIORITY.

/* Global task handles */
TaskHandle_t xTask1Handle = NULL;
TaskHandle_t xTask2Handle = NULL;
TaskHandle_t xTask3Handle = NULL;

void vTask1( void *pvParameters )
{
    for( ;; )
    {
        // Wait indefinitely for a notification
        ulTaskNotifyTake( pdTRUE, portMAX_DELAY );
        
        // Notification received: process button event
        //  Task1 logic
    }
}

void vTask2( void *pvParameters )
{
    for( ;; )
    {
        // Wait indefinitely for a notification
        ulTaskNotifyTake( pdTRUE, portMAX_DELAY );
        
        // Notification received: process button event
        // Task2 logic
    }
}

void vTask3( void *pvParameters )
{
    for( ;; )
    {
        // Task3 logic
    }
}

/* Hardware interrupt handler for the button */
void ButtonPress_IRQHandler( void )
{
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    
    // Clear the interrupt flag (MCU/hardware specific)
    ClearButtonInterruptFlag();
    
    // Notify Task 1 and Task 2 that the button was pressed
    vTaskNotifyGiveFromISR( xTask1Handle, &xHigherPriorityTaskWoken );
    vTaskNotifyGiveFromISR( xTask2Handle, &xHigherPriorityTaskWoken );
    
    // Force a context switch if any task was woken up
    portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
}

int main( void )
{
    // System and hardware initialization
    HardwareInit();
    
    // Create 3 tasks at the same priority
    xTaskCreate( vTask1, "Task1", configMINIMAL_STACK_SIZE, NULL, 1, &xTask1Handle );
    xTaskCreate( vTask2, "Task2", configMINIMAL_STACK_SIZE, NULL, 1, &xTask2Handle );
    xTaskCreate( vTask3, "Task3", configMINIMAL_STACK_SIZE, NULL, 1, &xTask3Handle );
    
    // Start the scheduler
    vTaskStartScheduler();
    
    // Should never reach here.
    for( ;; );
}
2 Likes
4

@bhoomrs and @aggarg Thanks for your reply, I will check and update you ASAP.

5

Hi @bhoomrs,

Thanks for sharing it works fine as I wish and itā€™s working using without semaphore :+1:

One more thing I will ask you that what is the difference between semaphore and the notification (that you shared me).

6

Glad it helped!

Task notifications and binary semaphores both serve as synchronization mechanisms in FreeRTOS. Task notifications are a lightweight, faster alternative when a single task needs to be signaled directly, making them ideal for one-to-one task communication. Unlike semaphores, they do not require a separate storage object and operate directly on the receiving task, reducing overhead. Binary semaphores allow multiple tasks to wait on the same event, with priority-based or first-come-first-served access, making them more flexible for complex synchronization needs.
Task notifications are preferable in scenarios with a fixed sender-receiver pair, while binary semaphores remain necessary when multiple tasks need to compete for a resource or when the waiting task is unknown in advance.

You can read the FreeRTOS documentation on task notifications and this forum thread for a comprehensive answer.

7

Thanks, It really helpful.

Sorry, for asking this question in this thread in advance
Would you share me some useful reference books or websites for tutorial, in which I can take guide for my projects.

8

You can check out the ā€˜FreeRTOS Reference Manualā€™ and ā€˜Mastering the FreeRTOS-Kernelā€™ for in-depth learning.
If youā€™re just starting out, explore the Beginnerā€™s Guide to FreeRTOS.
For hands-on experience, the FreeRTOS Tutorials (Lab Project) are a great resource.

Hope this helps!