Working of SoftwareTImers

Kernel
1

Hi,

I was testing SoftwareTimer in metware SYNOPSYS ARC IDE. I am following the example program given in the FreeRTOS Manuel. which like this…

CASE 1:

void vTimerCallback( TimerHandle_t xTimer )
{
printf(“callback function\n”):
…….
…….
}
void main( void )
{
TimerHandle_t xTimers = NULL;

    xTimers = xTimerCreate( "Timer",10,pdTRUE, ( void * ) 0,vTimerCallback );
    vTaskStartScheduler();

}

for this I am able to see the print “callback function” in the Resrult only once.

CASE 2 : if I I created a timer in the Task, like as shown in the following…

void vTimerCallback( TimerHandle_t xTimer )
{
printf(“callback function”):
…….
…….
}
void main( void )
{
TaskHandle_t xTask1Handle1 = NULL;

   xTaskCreate( prvTask1, "Tsk1Work", TASK1_STACK_SIZE, (void*)pcTextForTask1, 12, &xTask1Handle1 );

    vTaskStartScheduler();

}

void prvTask1( void *pvParameters )
{
printf("task is created\n);

    TimerHandle_t xTimers = NULL;

    xTimers = xTimerCreate( "Timer",10,pdTRUE, ( void * ) 0,vTimerCallback );

}

in this example I am able to see the “callback function” prints infinite time until I stop the timer.

Why this type of behaviour?, is it we have to create a timer in the Task to work as Auto Reloud Timers. or if I create that in the main function it is behaving as one shot Timer.

above case2 example is printing infinite times, so as shown in example code of FreeRTOS Manuel I gave the condition like count is 30 then timer should stop. after writing this condition the case 2 also printing only once.

please tell the reason behind this or else any mistakes I am doing to test the Timers…

in the freeRTOSConfig.h I have defined Like this

#define configTICK_RATE_HZ ( ( TickType_t ) 1000 )
#define configUSE_TIMERS 1
#define INCLUDE_xTimerPendFunctionCall 1
#define configTIMER_TASK_STACK_DEPTH 104
#define configTIMER_QUEUE_LENGTH 10
#define configTIMER_TASK_PRIORITY 10

Thanks and Regards…
Mansoor Basha

2

Be careful about defining variables in the main function with FreeRTOS. Some of the ports will reuse the main stack for the ISR stack, and variables in it are overwritten by the ISRs. This is possibly your issue here.

Also, using printf in the timer callback is not advised, as timer callback functions are run in the context of the timer task, and are not supposed to block, which printf might do, or because printf can use a lot of stack, you might be overflowing the timer task stack.