The OS and everything completely crashes and stops running.  Here is the scenario: Task A uses the SPI bus. Task B also uses the SPI bus. Again with Task C. Task A can take the semaphore, no problems. Always works. If Task B or Task C tries to take the semaphore, the whole OS crashes. Every time, even is Task A is not doing anything at the moment.

Make sure that you have released the semaphore in Task-A. xSemaphoreGive( xSemaphore ); Have a look @ user documnetaion in www.freertos.org Example usage: xSemaphoreHandle xSemaphore = NULL; void vATask( void * pvParameters ) {     // Create the semaphore to guard a shared resource.  As we are using     // the semaphore for mutual exclusion we create a mutex semaphore     // rather than a binary semaphore.     xSemaphore = xSemaphoreCreateMutex();     if( xSemaphore != NULL )     {         if( xSemaphoreGive( xSemaphore ) != pdTRUE )         {             // We would expect this call to fail because we cannot give             // a semaphore without first "taking" it!         }         // Obtain the semaphore – don’t block if the semaphore is not         // immediately available.         if( xSemaphoreTake( xSemaphore, ( portTickType ) 0 ) )         {             // We now have the semaphore and can access the shared resource.             // …             // We have finished accessing the shared resource so can free the             // semaphore.             if( xSemaphoreGive( xSemaphore ) != pdTRUE )             {                 // We would not expect this call to fail because we must have                 // obtained the semaphore to get here.             }         }     } } Regards, Prithwee

I will put the code in to check, but I do give it back in all instances. Any idea why the whole OS crashes though?

Did you locked your SPI Read/Write properly? Post your sample code here…. It may help you!!!

I will put the code in to check, but I do give it back in all instances. Any idea why the whole OS crashes though?