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> Why isn't this code behaving as it should?
post Nov 06, 2017, 01:58 AM
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I am new to embedded C and been struggling with it for a while now. The desired output for this project is: When SW1 is not pressed, the blue LED must be on. When SW1 is pressed the blue LED should turn on and off every 100ms. I wrote this code but it doesn't seem to be working properly. I tried it on the simulator and the LED toggles but the delay is more than 100ms, it's like a second. And on the real board, I get random results, sometimes it doesn't turn off and sometimes it changes color to purple. Why isn't this code behaving as it should? Why am I getting random results?

// BranchingFunctionsDelays.c Lab 6
// Runs on LM4F120/TM4C123
// Use simple programming structures in C to
// toggle an LED while a button is pressed and
// turn the LED on when the button is released.  
// This lab will use the hardware already built into the LaunchPad.
// Daniel Valvano, Jonathan Valvano
// January 15, 2016

// built-in connection: PF0 connected to negative logic momentary switch, SW2
// built-in connection: PF1 connected to red LED
// built-in connection: PF2 connected to blue LED
// built-in connection: PF3 connected to green LED
// built-in connection: PF4 connected to negative logic momentary switch, SW1

#include "TExaS.h"

#define GPIO_PORTF_DATA_R       (*((volatile unsigned long *)0x400253FC))
#define GPIO_PORTF_DIR_R        (*((volatile unsigned long *)0x40025400))
#define GPIO_PORTF_AFSEL_R      (*((volatile unsigned long *)0x40025420))
#define GPIO_PORTF_PUR_R        (*((volatile unsigned long *)0x40025510))
#define GPIO_PORTF_DEN_R        (*((volatile unsigned long *)0x4002551C))
#define GPIO_PORTF_AMSEL_R      (*((volatile unsigned long *)0x40025528))
#define GPIO_PORTF_PCTL_R       (*((volatile unsigned long *)0x4002552C))
#define SYSCTL_RCGC2_R          (*((volatile unsigned long *)0x400FE108))
#define SYSCTL_RCGC2_GPIOF      0x00000020  // port F Clock Gating Control

// basic functions defined at end of startup.s
void DisableInterrupts(void); // Disable interrupts
void EnableInterrupts(void);  // Enable interrupts
void portF_init(void);
void delay100ms(unsigned long time);

int main(void)
        unsigned long volatile delay;
      // activate grader and set system clock to 80 MHz
        TExaS_Init(SW_PIN_PF4, LED_PIN_PF2);  
        // set PF2
        GPIO_PORTF_DATA_R |= 0x04;
              // if switch PF4 is pressed and LED is ON (00000101)
            if( GPIO_PORTF_DATA_R == 0x05)
                      // turn LED OFF (clear bit)
                      GPIO_PORTF_DATA_R &= ~0x04;
                // if switch PF4 is pressed and LED is OFF (00000001)
                else if (GPIO_PORTF_DATA_R == 0x01)
                        // set PF2 - turn LED ON
                      GPIO_PORTF_DATA_R |= 0x04;
                        // set PF2
                        GPIO_PORTF_DATA_R |= 0x04;

void portF_init(void)
        volatile unsigned long delay;
        SYSCTL_RCGC2_R |= 0x00000020;     // 1) F clock
        delay = SYSCTL_RCGC2_R;           // delay  
        GPIO_PORTF_AMSEL_R = 0x00;        // 3) disable analog function
        GPIO_PORTF_PCTL_R = 0x00000000;   // 4) GPIO clear bit PCTL  
        GPIO_PORTF_DIR_R = 0x04;          // 5) PF4 input, PF2 output  
        GPIO_PORTF_AFSEL_R = 0x00;        // 6) no alternate function
        GPIO_PORTF_PUR_R = 0x01;          // disble pull-up resistor
        GPIO_PORTF_DEN_R = 0x14;          // 7) enable digital pins PF4 & PF2        

void delay100ms(unsigned long time)
        unsigned long i;
        while(time > 0)
                i = 1333333;  // this number means 100ms
                while(i > 0)
                        i = i - 1;
                time = time - 1; // decrements every 100 ms

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