8 years, 5 months ago.

Buttons on the mbed TestBed

So we wrote this program in class that's supposed to turn one of the LEDs on the LPC1768 on/off using the buttons on the TestBed. My question is in regards to how the bits in the FIOPIN register change when the buttons are pressed. This is the program(I'm using the keil compiler, I hope that's ok):

LPC_PINCON->PINSEL3 = LPC_PINCON->PINSEL3 & 0xFFFFFCF; //setting LED as GPIO
LPC_GPIO1->FIODIR = LPC_GPIO1->FIODIR |(1<<18); //setting LED as output
LPC_GPIO1->FIOSET = LPC_GPIO1->FIOSET| (1<<18); //Turning LED on(This line may be redundant at this position)
//the buttons BTN1 and BTN2 are by default set to input

while(1){
    if ((((LPC_GPIO0->FIOPIN)>>16)&0x1)==0){
        wait(200); //debounce
        LPC_GPIO1->FIOSET |= (1<<LED0);
    }
    else if(!(((LPC_GPIO0->FIOPIN)>>6)&0x1)){
        wait(200); //debounce
        LPC_GPIO1->FIOCLR |= (1<<LED0);
    }

Based on my understanding of how the buttons work, this is how I assume the program will run: PS: BTN1 is at P0.6 and BTN2 is at P0.16 1. When the program starts(before any buttons are pressed) FIOPIN bits 6 and 16 are both 0. So the LED is on. 2. Assume we press BTN2. Then FIOPIN bit 6 is 0, and bit 16 is 1, so LED turns off. 3. Now press BTN1. Bit 6 is now 1 and bit 16 is still 1. LED is still off. 4. Press BTN2. Bit 6 is still 1, but bit 16 is now 0. LED will turn on.

Is this correct? PS: I don't have access to the microcontroller at home, that's why I'm assuming and simulating what would/might happen if so and so.

My assumption is that the buttons aren't press and hold buttons, i.e. when you press a button it's state(1/0) gets changed in the FIOPIN register till it gets pressed again.