/ Read a switch and write it to the LED /

/ This program reads SW1 of Tiva LaunchPad and writes the inverse of the value to the green LED. SW1 is low when pressed (Normally High). LED is on when high. / void delayMs(int n) { int i, j; for(i = 0 ; i < n; i++) for(j = 0; j < 3180; j++) {} / do nothing for 1 ms / }

include "TM4C123GH6PM.h"

int main(void) { int i, j; unsigned int value; SYSCTL->RCGCGPIO |= 0x20; / enable clock to GPIOF / GPIOF->DIR = 0x0E; / set PORTF3 pin as output (LED) pin / / and PORTF4 as input, SW1 is on PORTF4 / GPIOF->DEN = 0x1E; / set PORTF pins 4-3 as digital pins / GPIOF->PUR = 0x10; / enable pull up for pin 4 / while(1) {
value = GPIOF->DATA; / read data from PORTF / // value = ~value; / switch is low active; LED is high active / // value = value >> 1; / shift it right to display on green LED / // GPIOF->DATA = value; / put it on the green LED / if(!value) { GPIOF->DATA = 0x08;

for(i = 0 ; i < 3000; i++)
    for(j = 0; j < 3180; j++)
        {}  /* do nothing for 1 ms */
                            GPIOF->DATA = 0x04;
            for(i = 0 ; i < 3000; i++)
    for(j = 0; j < 3180; j++)
        {}  /* do nothing for 1 ms */
                            GPIOF->DATA = 0x02;
            for(i = 0 ; i < 3000; i++)
    for(j = 0; j < 3180; j++)
        {}  /* do nothing for 1 ms */
        }
        else
        {
            GPIOF->DATA = 0x00;
        }
}

}

/ This function is called by the startup assembly code to perform system specific initialization tasks. /

void SystemInit(void) { / Grant coprocessor access / / This is required since TM4C123G has a floating point coprocessor / SCB->CPACR |= 0x00F00000; }