5. Tracing User Events

• ue1 will be used to monitor the count value in Task_1
• ue2 will be used for general purpose messages from Task_2

// Trace User Events Channels
traceString ue1, ue2;

Then, in the body of main(), before the scheduler is started, we need to register the user event channels:

...
	// Register the Trace User Event Channels
	 ue1 = xTraceRegisterString("count");
	 ue2 = xTraceRegisterString("msg");
...

Now we can use ue1 and ue2 channel to issue printf-like messages into the recorder.

Let us print out the value of count in Task_1:

/*
 *	Task_1 toggles LED every 10ms
 */
void vTask1 (void *pvParameters)
{
	portTickType	xLastWakeTime;

	uint16_t	count;
	count = 0;

	// Initialize timing
	xLastWakeTime = xTaskGetTickCount();

	while(1)
	{
		// Toggle LED only if button is released
		if (!BSP_PB_GetState())
		{
			BSP_LED_Toggle();
			count++;
		}

		// Release semaphore every 10 count
		if (count == 10)
		{
			xSemaphoreGive(xSem);
			count = 0;
		}

		// Send count value into trace UEC
		vTracePrintF(ue1, "%d", count);

		// Wait here for 10ms since last wakeup
		vTaskDelayUntil (&xLastWakeTime, (10/portTICK_RATE_MS));
	}
}

And display a cool message whenever the semaphore was successfully taken in Task_2:

/*
 *	Task_2 sends a message to console when xSem semaphore is given
 */
void vTask2 (void *pvParameters)
{
	portBASE_TYPE	xStatus;
	uint16_t 		count;

	count = 0;

	// Take the semaphore once to make sure it is empty
	xSemaphoreTake(xSem, 0);

	while(1)
	{
		// Wait here for Semaphore with 2s timeout
		xStatus = xSemaphoreTake(xSem, 2000);

		// Test the result of the take attempt
		if (xStatus == pdPASS)
		{
			// The semaphore was taken as expected
			vTracePrint(ue2, "Yep!");

			// Display console message
			my_printf("Hello %2d from task2\r\n", count);
			count++;
		}

		else
		{
			// The 2s timeout elapsed without Semaphore being taken

			// Display another message
			my_printf("Hey! Where is my semaphore?\r\n");
		}
	}
}

Note that we used both vTracePrint() and vTracePrintF() functions. vTracePrint() is faster but it doesn't format numbers.

And now the result (yellow tags):