I need a fast way of waking a task from an interrupt, notify is tick based and is too slow

Kernel
1

Hi All,

I’m using Version 90 and I have a problem that requires a receive interrupt that must wake up a waiting task very quickly. The xTaskNotifyWait() function does not wake the task until the next system tic ( @ 0-1mSec.). I need a way to wake the task reliably in 50uSec. or so.

Any ideas would be appreciated. Thanks in advance!

2

Use the xHigherPriorityTaskWoken parameter and, assuming you have preemption enabled, the interrupt will return directly to the woken task - not on the next tick interrupt. See the API documentation for details. I would provide a link but am not at my computer right now.

1 Like
3

Thank you for this helpful idea. I will give it a try.

4

Hi Richard,

Your idea works perfectly. The response is less than 10uSec. Here is the code for others:

Interrupt code:
if(SCI3.SSR.BIT.PER == 0){ //all OK
xHigherPriorityTaskWoken = pdFALSE;
xTaskNotifyFromISR(xIPCTaskHndl,0, 0, &xHigherPriorityTaskWoken);
portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

Task code:
if(xTaskNotifyWait(0,0,0,5)){ //wait for an rx wakeup timeout
//woken by an rx interrupt
asm (“NOP”);
}else{
//woken by a timeout
asm (“NOP”);
}