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Problems with passing parameters to task

Posted by dennis on February 7, 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

RE: Problems with passing parameters to task

Posted by Richard on February 7, 2007
You are passing the address of a variable that is allocated on the stack of a function - and therefore is only temporary.

Regards.

RE: Problems with passing parameters to task

Posted by dennis on February 8, 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


RE: Problems with passing parameters to task

Posted by dennis on February 8, 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

RE: Problems with passing parameters to task

Posted by raedbenz on 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?

RE: Problems with passing parameters to task

Posted by raedbenz on December 1, 2009
sorry, last post sorted..thanks


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