TM4C1294NCPDT: TI-RTOS for TIVA c question

Hi Patrick,

  The interrupt which is managed as Hwi will have higher priority than a task. What might have happened is that the bouncing switch will create multiple interrupts in short duration that can preempt the task from disabling the timer. Even if the timer is disabled, the bouncing can continue to occur. 

  Please take a look at the below code that implements a simple software debounce. Although this is written for FreeRTOS, you can use the same idea for TI-RTOS. Look at vSW1Handler where it de-bounces the switch with a 200ms software filter.  

/* Standard includes. */
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>

/* Kernel includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "semphr.h"

/* Hardware includes. */
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/sysctl.h"
#include "drivers/rtos_hw_drivers.h"
#include "utils/uartstdio.h"


/* Priorities at which the tasks are created. */
#define mainSEMAPHORE_TASK_PRIORITY     ( tskIDLE_PRIORITY + 1 )

/* The semaphore used by both tasks. */
SemaphoreHandle_t ButtonIntSemaphore;

/*-----------------------------------------------------------*/
/*
 * The tasks as described in the comments at the top of this file.
 */
static void prvTaskLedon( void *pvParameters );
static void prvTaskLedoff( void *pvParameters );

/* Time Stamp variable */
uint32_t g_ui32preTimeStamp;

/*
 * Called by main() to create the simply blinky style application
 */
void vBlinkyTask( void );

/* 
 * Configure a button to generate interrupts
 */
static void prvConfigureButton( void );

/*-----------------------------------------------------------*/

/* Called by main() to create the simply blinky style application */

void vBlinkyTask( void )
{
    /* Configure a button to generate interrupts. */
	prvConfigureButton();

    /* Create a binary semaphore. */
    ButtonIntSemaphore = xSemaphoreCreateBinary();

    if( ButtonIntSemaphore != NULL )
    {
        /* Start the two tasks as described in the comments at the top of this
        file. */
        xTaskCreate(prvTaskLedon,                      /* The function to turn ON LED */
                    "Ledon",                           /* The text name assigned to the task. */
                    configMINIMAL_STACK_SIZE,          /* The size of the stack to allocate to the task. */
                    NULL,                              /* No parameter passed to the task */
                    mainSEMAPHORE_TASK_PRIORITY ,      /* The priority assigned to the task. */
                    NULL );                            /* The task handle is not required, so NULL is passed. */

         xTaskCreate(prvTaskLedoff,                    /* The function to turn OFF LED */
                    "Ledoff",                          /* The text name assigned to the task. */
                    configMINIMAL_STACK_SIZE,          /* The size of the stack to allocate to the task. */
                    NULL,                              /* The priority assigned to the task. */
                    mainSEMAPHORE_TASK_PRIORITY,       /* The task handle is not required, so NULL is passed. */
                    NULL );
	}
}
/*-----------------------------------------------------------*/

/*
 * Task to turn ON LEDs
 */
static void prvTaskLedon( void *pvParameters )
{
    (void) pvParameters;
    uint32_t counter = 0;

    while (1)
    {
        if (xSemaphoreTake(ButtonIntSemaphore, portMAX_DELAY) == pdPASS)
        {
            UARTprintf("Turn on LED\n");
            if (counter % 3 == 0)
            {
                LEDWrite(BLUE_LED|RED_LED|GREEN_LED, BLUE_LED);
            }
            else if (counter % 3 == 1)
            {
                LEDWrite(BLUE_LED|RED_LED|GREEN_LED, RED_LED);
            }
            else if (counter % 3 == 2)
            {
                LEDWrite(BLUE_LED|RED_LED|GREEN_LED, GREEN_LED);
            }
            counter++;
        }
    }
}
/*-----------------------------------------------------------*/

/*
 * Task to turn OFF LEDs
 */
static void prvTaskLedoff( void *pvParameters )
{
    (void) pvParameters;

    while (1)
    {
        if (xSemaphoreTake(ButtonIntSemaphore, portMAX_DELAY) == pdPASS)
        {
            UARTprintf("Turn off LED\n");
            LEDWrite(BLUE_LED|RED_LED|GREEN_LED, 0);
        }

    }
}
/*-----------------------------------------------------------*/

static void prvConfigureButton( void )
{
    /* Configure buttona SW1 and SW2 to generate interrupts. */

    /* Initialize the LaunchPad Buttons. */
    ButtonsInit();

    /* Configure both switches to trigger an interrupt on a falling edge. */
    GPIOIntTypeSet(BUTTONS_GPIO_BASE, ALL_BUTTONS, GPIO_FALLING_EDGE);

    /* Enable the interrupt for Port J in the GPIO peripheral. */
    GPIOIntEnable(BUTTONS_GPIO_BASE, ALL_BUTTONS);

    /* Enable the Port J interrupt in the NVIC. */
    IntEnable(INT_GPIOF);

    /* Enable global interrupts in the NVIC. */
    IntMasterEnable();
}
/*-----------------------------------------------------------*/

void vSW1Handler( void )
{
uint32_t ui32Status;
BaseType_t  xHigherPriorityTaskWoken = pdFALSE;

    /* Read the Port J interrupt status to find the cause of the interrupt. */
    ui32Status = GPIOIntStatus(BUTTONS_GPIO_BASE, true);

	/* Clear the interrupt. */
    GPIOIntClear(BUTTONS_GPIO_BASE, ui32Status);

    /* Debounce the input with 200ms filter */
    if ((xTaskGetTickCount() - g_ui32preTimeStamp ) > 200)
    {
        UARTprintf("Semaphore is given\n");
        xSemaphoreGiveFromISR(ButtonIntSemaphore, &xHigherPriorityTaskWoken);
    }

    g_ui32preTimeStamp = xTaskGetTickCount();


}
/*-----------------------------------------------------------*/

void vApplicationTickHook( void )
{
    /* This function will be called by each tick interrupt if
		configUSE_TICK_HOOK is set to 1 in FreeRTOSConfig.h.  User code can be
		added here, but the tick hook is called from an interrupt context, so
		code must not attempt to block, and only the interrupt safe FreeRTOS API
		functions can be used (those that end in FromISR()). */

    /* Only the full demo uses the tick hook so there is no code is
		executed here. */
}