Turn led on when both switches are pressed - c

Question

I'm trying to turn the led on in my tiva launchpad(tm4c123).
Current code :
while (1)
{
switch(GPIO_PORTF_DATA_R & 0x11) // 0x11 = 10001
{
case 0x00: //both switches are pressed
{
GPIO_PORTF_DATA_R = 0x02; // turn on the red led
break;
}
case 0x01: //SW1 is pressed, SW2 is not pressed
{
GPIO_PORTF_DATA_R = 0x04; // turn on the blue led
break;
}
case 0x10: //SW2 is pressed, SW1 is not pressed
{
GPIO_PORTF_DATA_R = 0x08; // turn on the green led
break;
}
default:
GPIO_PORTF_DATA_R = 0;
break;
}
}
Without this two lines of code, this is what happens :
The board start with the green led on.
When I press both or only SW2 nothing happens.
When I press SW1 the red led turn on.
Could someone explain to me why?
GPIO_PORTF_LOCK_R = 0x4C4F434B;
GPIO_PORTF_CR_R = 0x1F;

Answer 1

You can read your switches on your tiva launchpad like this:
SW1 = GPIO_PORTF_DATA_R&0x10; // read PF4 into SW1
SW2 = GPIO_PORTF_DATA_R&0x01; // read PF0 into SW2
Then you can check the status of those inputs and make decisions.
if (!SW1 && !SW2) { // both pressed
GPIO_PORTF_DATA_R = 0x04;
} else if (!SW1) { // SW1 pressed
GPIO_PORTF_DATA_R = 0x02;
} else if (!SW2) { // SW2 pressed
GPIO_PORTF_DATA_R = 0x08;
} else { // neither
GPIO_PORTF_DATA_R = 0x00;
}
If you look at the TM4C123GH6PM datasheet, on page 205, it says;
Protection is provided for the GPIO pins that can be used as the four
JTAG/SWD pins
If you check the signal tables on page 1329, you will see that PF0 ,where one of your switches is connected to, is one of them. So you need to unlock it.
On page 684, it says
Writing 0x4C4F.434B to the GPIOLOCK register unlocks the GPIOCR
register.