为什么按下 MSP430 上的按钮不点亮 LED

Question

Pin 1.3step counter: Modify the code to have the LEDs step one binary order each time the button has been pushed.

I'm relatively new with programming on a Micro Controller. So what is above is what I'm attempting to do. However while trying to get it to step in binary order, the button has seemed to stop working and thus none of the LEDs flash. I'm uncertain what changed since previously it ran well without the button push. Comparing with friends it looks the same so stumped on what went wrong.

This is the code I have.

#include <msp430.h> 


/*
 * main.c
 */
int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop watchdog timer

  volatile unsigned int i;
  volatile unsigned int j;

  P1DIR |= 0x41;                            // Set P1.0 to output direction
  P1DIR &=~(BIT3);                          // Ensure P1.3 is an input
  P1REN |= BIT3;                            // Set pulling Resistor for P1.3
  P1OUT |= BIT3;                            // Make the pulling resistor for P1.3 a pull-UP resistor
  j=0;                                      // Button presses set to 0
  P1OUT &=~0x01;

  while (1)                                 // Test P1.3
  {
    if ((BIT3 & P1IN)) {                    // if P1.3 set, set P1.0 turning on the LED
        if (j == 0)
            P1OUT &= ~0x41;
        if (j == 1) {
            P1OUT |= 0x01;
            P1OUT &= ~0x40;
        }
        if (j == 2) {
            P1OUT &= ~0x01;
            P1OUT |= 0x40;
        }
       if (j == 3)
           P1OUT |= 0x41;
    else {
        for (i=3000; i>0; i--);
        if (j == 3)
            j++;
        else
            j = 0;
        }
       while ((BIT3 & P1IN));

  }
}
}

Answer 1

You only increase j if j == 3 . So j always stays at 0, which means all LEDs off. You also missed a closing brace before the else. Formatting the code with correct indentation helps finding such errors.

  while (1)
  {
    if ((BIT3 & P1IN)) 
    {
      if (j == 0)
      {
        P1OUT &= ~0x41;
      } 

      if (j == 1) 
      {
        P1OUT |= 0x01;
        P1OUT &= ~0x40;
      }

      if (j == 2) 
      {
         P1OUT &= ~0x01;
         P1OUT |= 0x40;
      }

      if (j == 3)
      {
         P1OUT |= 0x41;
      }
    }
    else 
    {
       for (i=3000; i>0; i--);

       // here I exchanged the == with <
       if ( j < 3 ) 
       {
         j++;
       }
       else
       {
         j = 0;
       }
    }
    while ((BIT3 & P1IN));
 }