FreeRTOS Sempahore from ISR not working

Question

I need to make a data accusition device whose one task is to samples some GPIO's and record the GPIO status and send it to PC via UART to display in PC. The algorithm i chose was (please correct me since iam very novice in RTOS) to create a timer running at 1us and then poll the status of all GPIO needed. For that i used a timer in the freertos demo. And give a semaphore in the timer ISR which should call a task which do all the remaining job.

Don't know why but the code i edited dont work

My main() is

int main(void) {
  /* Prepare the hardware to run this demo. */
  prvSetupHardware();

  vSemaphoreCreateBinary(SemaphoreTask);
  if( SemaphoreTask != NULL )
  {
    xTaskCreate( SemaphoreTakeTask, "SemaphoreTakeTask", 240, NULL , 3, NULL );
    vTaskStartScheduler();
  }
  for(;;);
  return 0;
}

Task 1 a dummy function i wrote just to try out if semaphore is working

void SemaphoreTakeTask(void* parameter){
  vSetupTimerTest(10);                 // Timer initialization function in FreeRtos DEMO
  TRISEbits.TRISE6 = 0;                // Set the GPIO as Output
  xSemaphoreTake( SemaphoreTask, 0 );  // As mentioned in user guide just take the semaphore once to clear the semaphore at start
  for(;;){
    xSemaphoreTake( SemaphoreTask, portMAX_DELAY );
    LATEbits.LATE6 ^= 1;               // Toggle an IO to see whether its working
  }
}

Timer ISR handler

void vT2InterruptHandler(void) {
  portBASE_TYPE xHigherPriorityTaskWoken = pdFALSE;
  /* Clear the timer interrupt. */
  IFS0CLR = _IFS0_T2IF_MASK;
  xSemaphoreGiveFromISR(SemaphoreTask, &xHigherPriorityTaskWoken);
  if (xHigherPriorityTaskWoken != pdFALSE) {
    portEND_SWITCHING_ISR(xHigherPriorityTaskWoken);
  }
}

When i put break point in the ISR handler it comes there but the GPIO is not toggling (which i placed in Task 1)

Iam a novice in RTOS so please pardon me if i missed any basic things in the code

I just need to give a semaphore from ISR handler

After some workouts i found that all the issue happens when xSemaphoreGiveFromISR is called. The control goes to a vAssertCalled function and stays in an infinite loop

xSemaphoreTake() is always returning pdFALSE

Answer 1

The priority of the interrupt has to be set to below configMAX_SYSCALL_INTERRUPT_PRIORITY

To get more clear idea see SourceForge Forum