Problems with passing parameters to task

Kernel
1

tcwden wrote on Wednesday, February 07, 2007:

Hi,

I’m experiencing a strange problem in passing parameters to a simple task of toggling an led. Below is my code:

//=================================================================================
const unsigned long SLEEP_TIME[] = {1000000, 3000000}; //sleep for 1 and 3 sec.

void tskFlashLED( void * ptr ) {
   unsigned int index = *((unsigned int*)ptr); //index of led
   for(;;){
      if(index < 2){
         vTaskDelay( (unsigned long)SLEEP_TIME[index]/(1000*portTICK_RATE_MS) );  //Delay for 1 or 3 sec
         if(led_status(index) == 0){
            led_on(index);        //Turn on led
         } else{
            led_off(index);        //Turn off led
         }
      }
   }
}

void vUserMain(){
   unsigned int arg1 = 0;    //Index
   xTaskCreate(tskFlashLED, NULL, configMINIMAL_STACK_SIZE, &arg1, tskIDLE_PRIORITY, NULL);
}
//=================================================================================

After debugging, I’ve found that the value of index not equals to arg1 (i.e. 0). Can anyone suggest what might be the problem? My port is dsPic30f5011

Many thanks!

Dennis

2

rtel wrote on Wednesday, February 07, 2007:

You are passing the address of a variable that is allocated on the stack of a function - and therefore is only temporary.

Regards.

3

tcwden wrote on Thursday, February 08, 2007:

Hi Richand,

Thank you very much for your prompt reply.

What can I do to work round the problem? In fact, I’ve already taken reference to the example code on BlockQ.c, and I’ve already saved a copy of the value when I enter the function as follow:

void tskFlashLED( void * ptr ) {
   unsigned int index = *((unsigned int*)ptr); //index of led
   …
}

Thank you in advance.

Dennis

4

tcwden wrote on Thursday, February 08, 2007:

Hi!

I’ve just figured out how to solve the problem.

Since $arg1 is reside in the function vUserMain(), on exit of the function, the local variable $arg1 will not be valid anymore. So $arg1 should either be global of declared static (as in dynamic.c).

Many thanks for your attention.

Dennis

5

raedbenz wrote on Monday, November 30, 2009:

hi,
is this allowed?

(hash)define LED1  0x0020

xTaskCreate(tskFlashLED, NULL, configMINIMAL_STACK_SIZE, (void*)LED1 , tskIDLE_PRIORITY, NULL);

i get this " invalid lvalue in unary ‘&’ "
Plz how can I get around this? use an defined value as an argument?

6

raedbenz wrote on Tuesday, December 01, 2009:

sorry, last post sorted…thanks