EK-TM4C123GXL: How to use the interrupt for SW1 (GPIO pin PF4) on the Tive C Series Launchpad (TM4C123G).

I'm attempting to write a program that will blink the blue LED on the board while SW1 is held down. I am trying to use interrupts to handle the state change, and have followed the example code posted here.

Here is my code:

#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include "inc/hw_memmap.h"
#include "driverlib/interrupt.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"


void onButtonDown(void);
void onButtonUp(void);

/**
 * Called when SW1 is pressed
 */
void onButtonDown(void) {
    if (GPIOIntStatus(GPIO_PORTF_BASE, false) & GPIO_PIN_4) {
        // PF4 was interrupt cause
        GPIOIntRegister(GPIO_PORTF_BASE, onButtonUp);   // Register our handler function for port F
        GPIOIntTypeSet(GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_RISING_EDGE);          // Configure PF4 for rising edge trigger
        GPIOIntClear(GPIO_PORTF_BASE, GPIO_PIN_4);  // Clear interrupt flag

        while(1) {
            GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, GPIO_PIN_2);
            SysCtlDelay(20000000);
            GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 0);
        }
    }
}

/**
 * Called when SW1 is released
 */
void onButtonUp(void) {
    if (GPIOIntStatus(GPIO_PORTF_BASE, false) & GPIO_PIN_4) {
        // PF4 was interrupt cause
        GPIOIntRegister(GPIO_PORTF_BASE, onButtonDown); // Register our handler function for port F
        GPIOIntTypeSet(GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_FALLING_EDGE);         // Configure PF4 for falling edge trigger
        GPIOIntClear(GPIO_PORTF_BASE, GPIO_PIN_4);  // Clear interrupt flag

        GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 0);
    }
}


/**
 * main.c
 */
int main(void)
{
    SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_INT | SYSCTL_XTAL_16MHZ);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
    while (!SysCtlPeripheralReady(SYSCTL_PERIPH_GPIOF))
    {
    }


    // Output pin F2 setup (LED)
    GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_2);


    // Input Pin F4 setup (SW1)
    GPIOPinTypeGPIOInput(GPIO_PORTF_BASE, GPIO_PIN_4);
    GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD_WPU);

    GPIOIntDisable(GPIO_PORTF_BASE, GPIO_PIN_4);
    GPIOIntClear(GPIO_PORTF_BASE, GPIO_PIN_4);

    GPIOIntRegister(GPIO_PORTF_BASE, onButtonDown);
    GPIOIntTypeSet(GPIO_PORTF_BASE, GPIO_PIN_4, GPIO_FALLING_EDGE); // Configure PF4 for falling-edge trigger
    GPIOIntEnable(GPIO_PORTF_BASE, GPIO_PIN_4);

	while(1);
}

I have two issues.

The first is that when SW1 is being held down, the blue LED should be blinking on and off, but the LED only remains on.

The second issue is that the interrupt onButtonUp() is never being triggered after SW1 is released, and the program stays stuck in the while loop in onButtonDown().

Any help or tips on what I'm doing wrong would be appreciated.

Details:

Code Composer Version: 8.1.0.00011

TivaWare version 2.1.4.178

Compiler: TI v18.1.3

Apologies for any mistakes made in the post.