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Is this ok? getSemaphoreSPI();

Posted by Willem on February 9, 2009
Hi,

I have created this function to get the semaphore:

unsigned char getSemaphoreSPI(void)
{
if(xSemaphoreSPI != NULL)
{
if( xSemaphoreTake( xSemaphoreSPI, ( portTickType ) 10000 ) == pdTRUE ) // try to take the sem., block max. 10sec
{
return pdTRUE;
}
}
return pdFALSE;
}

I have 3 different tasks that try to take this semaphore, it is possible that they come all at the same time.

Is there a limit on the number of tasks that are requesting a mutex?

RE: Is this ok? getSemaphoreSPI();

Posted by Dave on February 9, 2009
The function looks fine and there is no limit on how many tasks can call the function. However other than checking that the semaphore is not null, your function just returns what xSemaphoreTake() returns, so why not just call xSemaphoreTake() directly.

RE: Is this ok? getSemaphoreSPI();

Posted by Prithwee on February 9, 2009

I think Something like this code will do !!

if( xSemaphoreSPI != NULL ){
if( xSemaphoreTake(xSemaphoreSPI ,( portTickType )BLOCK_TIME)){
/*
Shared resources or functions here....
*/
xSemaphoreGive( xSemaphoreSPI );
}
}

>>I have 3 different tasks that try to take this semaphore, it is possible that they come all at the same time.
> 3 different tasks cant access the shared resources at same time.

>>Is there a limit on the number of tasks that are requesting a mutex?
> NO Limit.

Regards,
Prithwee

RE: Is this ok? getSemaphoreSPI();

Posted by Willem on February 9, 2009
I have other task that then uses this function like this:

void setRelay(unsigned char setRelayNo, unsigned char onOff )
{
if( (getSemaphoreSPI() == pdTRUE) )
{
// critical code
xSemaphoreGive( xSemaphoreSPI );
}

and

void pwm1SwitchDirection(unsigned char direction)
{
if(getSemaphoreSPI() == pdTRUE)
{
// critical code
xSemaphoreGive( xSemaphoreSPI );
}
etc.





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