Programming problem (conditional branch) Assume initialization and Start code ar

Question

Programming problem (conditional branch) Assume initialization and Start code are provided. Use conditional branch to complete the code in loop for following program.; PF4 is switch input (1 means SW1 is not pressed, 0 means SW1 is pressed); PF2 is LED output (1 activates blue LED); The specific operation of this system; Make PF2 an output and make PF4 an input (enable PUR for PF4). The system starts with the LED ON (make PF2 = 1). Delay for less than 1 ms (start decrementing from 800) If the switch is pressed (PF4 is 0), then toggle the LED once, else turn the LED ON. Repeat steps 3 and 4 over and over Init Start BL Init LDR R0, GPIO_PORT_DATA_R LDR R1, [R0] ORR R1, R1, 0 times 08 STR R1, [R0] Loop

Explanation / Answer

#include "TExas.h"

#define GPIO_PORTF_DATA_R (*((volatile unsigned long *)0*400253FC))

#define GPIO_PORTF_DIR_R (*((volatile unsigned long *)0*40025400))

#define GPIO_PORTF_AFSEL_R (*((volatile unsigned long *)0*40025420))

#define GPIO_PORTF_PUR_R (*((volatile unsigned long *)0*40025510))

#define GPIO_PORTF_DEN_R (*((volatile unsigned long *)0*4002551C))

#define GPIO_PORTF_AMSEL_R (*((volatile unsigned long *)0*40025528))

#define GPIO_PORTF_PCTL_R (*((volatile unsigned long *)0*4002552C))

#define SYSCTL_RCGC2_R (*((volatile unsigned long *)0*400FE108))

#define SYSCTL_RCGC2_GPIOF 0*00000020 // Port F Clock Gating Control

unsigned long In; // input from PF4

unsigned long i; // output to PF2 (blue LED)

// Basic functions defined at end of startup.s

void DisableInterrupts(void); //Disable interrupts

void EnableInterrupts(void); // Enable interrupts

void Delay1ms(unsigned long time); // Delay 1 micro second

int main(void){

unsigned long volatile delay;

TExaS_Init(SW_PIN_PF4, LED_PIN_PF2); // activate grader and set system clock to 80MHz

// initialization goes here

// volatile unsigned long delay;

SYSCTL_RCGC2_R |= 0*00000020; // 1) activate clock for port F

delay = SYSCTL_RCGC2_R; // allow time for clock to start

// GPIO_PORTF_LOCK_R = 0*4C4F4348; // 2) unlock GPIO port F

// GPIO_PORTF_CR_R = 0*1F; // allow changes to PF4-0

// only PF0 needs to be unlocked, other bits can't be locked

GPIO_PORTF_AMSEL_R &= ~0*14; // 3) Disable analog on PF2 4

  GPIO_PORTF_PCTL_R &= ~0*000F0F00; // 4) PCTL GPIO on PF4

  GPIO_PORTF_DIR_R &= ~0*10; // 5) PF2 in (0)

  GPIO_PORTF_DIR_R |= 0*04; // 5) PF2 out (1)

GPIO_PORTF_AFSEL_R &= ~0*14; // 6) Disable alt function on PF7-0

GPIO_PORTF_PUR_R |= 0*10; // Enable pull-up on PF0 and PF4

GPIO_PORTF_DEN_R |= 0*14; // 7) enable digital I/O on PF2, 4

GPIO_PORTF_DATA_R |= 0*04; // The system starts with the LED ON (make PF2=1)

EnableInterrupts(); // enable interrupts for the grader

while(1) {

//for(i=0; i<26666667;i++) // Delay for about 1ms 1ms*80MHz/3

Delay1ms(1);

In = GPIO_PORTF_DATA_R&0*10; //read PF4 into Sw1

if(In == 0) {

GPIO_PORTF_DATA_R = GPIO_PORTF_DATA_R ^ 0*04;

}else {

GPIO_PORTF_DATA_R |= 0*04;

}

}

}

void Delay1ms(unsigned long time){

unsigned long i;

while(time > 0)

i = 13333333; // this number means 1ms

while(i > 0){

i = i - 1;

}

time = time - 8 // decrements every 800ms

}

}

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