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use function "xTaskGetTickCount" in interrupt

Posted by yukunduan on June 22, 2017

In our porject,cpu is STM32F103 ,we use the function xTaskGetTickCount in the interrupt of canRx,but sometimes it can not return from the function "USBLPCAN1RX0IRQHandler".Why and if we can use this function in the interrupt?It that ok?


use function "xTaskGetTickCount" in interrupt

Posted by yukunduan on June 22, 2017

Also ,it will always dead in the interrupt of STM32F103,but it's ok in STM32F407.


use function "xTaskGetTickCount" in interrupt

Posted by richarddamon on June 22, 2017

The function doesn't end if FromISR so it is not safe to use in an ISR. Depending on the port, sometimes it might work, or it might not.


use function "xTaskGetTickCount" in interrupt

Posted by heinbali01 on June 22, 2017

A bit more precisely: it depends on portTICK_TYPE_IS_ATOMIC.

Look at the function:

~~~ TickTypet xTaskGetTickCount( void ) { TickTypet xTicks;

/* Critical section required if running on a 16 bit processor. */
portTICK_TYPE_ENTER_CRITICAL();
{
	xTicks = xTickCount;
}
portTICK_TYPE_EXIT_CRITICAL();

return xTicks;

}

~~~

It may enter a critical section depending on portTICK_TYPE_IS_ATOMIC.

Suppose that xTickCount is a 32-bit variable, and suppose that the CPU is 32-bits, the copy will be "atomic", and no protection is needed. Your CPU, an STM32Fxxx is 32 bits, so it is safe to call xTaskGetTickCount(). Regards.


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