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Interrupt problem with vTaskDelay on LPC2478

Posted by specialk on June 22, 2009
I've been trying to get FreeRTOS working in Crossworks with a 2478, and can get everything to compile and run through the 'main' method properly. I can create a couple tasks and start the scheduler, but when I create two tasks with equal priorty, only the last task added will run continually (the first task never executes). As well, if I add 'vTaskDelay' to either task, the task stops running altogether and the other task will run exclusively. If I add vDelayTask in both tasks, they will each run once, and then nothing happens anymore.

I'm guessing that the problem is in the interrupt handling for the timer tick, but I'm hoping that someone with more experience would be able to confirm my suspicion or suggest another likely cause of this behaviour? Here is the task creation code and some sample task code just as an example ... in this case with no vTaskDelays, only the LED task will run continuously:

int main (void)
cpuSetupHardware ();
enableIRQ ();

xTaskCreate (vStatsTask, (const signed portCHAR * const) "Stats", 256, NULL, (tskIDLE_PRIORITY + 1), &taskHandles [TASKHANDLE_STATS]);
xTaskCreate (vLEDTask, (const signed portCHAR * const) "LEDs", 256, NULL, (tskIDLE_PRIORITY + 1), &taskHandles [TASKHANDLE_LED]);


return 0;

static void vLEDTask( void *pvParameters )
// Create 500ms delay between LED events
const portTickType xDelay = 500 / portTICK_RATE_MS;

for (;;)
// vTaskDelay(xDelay);

RE: Interrupt problem with vTaskDelay on LPC2

Posted by Dave on June 22, 2009
Agree it sounds like the tick interrupt is not running. The 2378 has a different timer setup to the smaller LPC2000 chips. See the difference in prvSetupTimerInterrupt() in the two files Source\portable\GCC\lpc2000\port.c and Source\portable\GCC\lpc23xx\port.c.

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