新人求教,急，

只看该作者 · 2011-11-8 19:05

帮忙看下：程序；
dir = -1,这句什么意思
还能给变量赋-1！！！；是不是把1右移一位啥的，
超级新手求解

只看该作者 · 2011-11-8 19:06

大侠们速来啊

只看该作者 · 2011-11-8 20:14

程序:#include <stdint.h>
#include "LPC17xx.h"

#define LED_NUM    8                   /* Number of user LEDs          */
const unsigned long led_mask[] = { 1UL<<0, 1UL<<1, 1UL<<2, 1UL<< 3,
                                 1UL<< 4, 1UL<< 5, 1UL<< 6, 1UL<< 7 };
int idxCur = -1;                         /* current led position from 0..7  */
int idxOld =  0;                         /* old    led position from 0..7  */
int dir =  1;                         /* direction for switching the LED */

/**
* @brief  Function that initializes Button INT0
*/
void BUTTON_init(void) {
  LPC_GPIO2->FIODIR    &= ~(1 << 10); /* PORT2.10 defined as input    */
  LPC_GPIOINT->IO2IntEnF |=  (1 << 10); /* enable falling edge irq       */

  NVIC_EnableIRQ(EINT3_IRQn);             /* enable irq in nvic             */
}

/**
* @brief  Function that initializes LEDs
*/
void LED_init(void) {
  LPC_GPIO2->FIODIR = 0x000000FF;       /* LEDs on PORT2 defined as Output */

  LPC_GPIO0->FIODIR |= 0x03f80000;
  LPC_GPIO0->FIOSET = 0x03f80000;
}

/**
* @brief  Function that turns on requested LED
*/
void LED_On (unsigned int num) {

  LPC_GPIO2->FIOPIN |= led_mask[num];
}

/**
* @brief  Function that turns off requested LED
*/
void LED_Off (unsigned int num) {

  LPC_GPIO2->FIOPIN &= ~led_mask[num];
}

/**
* @brief  Function that initializes Button INT0
*/
void EINT3_IRQHandler()
{
  LPC_GPIOINT->IO2IntClr |= (1 << 10);    /* clear pending interrupt       */

  /* Calculate 'idx': 0,1,...,LED_NUM-1,LED_NUM-1,...,1,0,0,... */
  idxCur += dir;
  if (idxCur == LED_NUM){ dir = -1; idxCur -=  2; }
  else if (idxCur < 0) {  dir =  1; idxCur +=  2; }

  LED_Off(idxOld);                      /* switch off old LED position  */
  LED_On (idxCur);                      /* switch on  current LED position */
  idxOld = idxCur;
}

/**
* @brief  Main Function
*/
int main (void)
{
   SystemInit();                         /* initialize system             */
   LED_init();
   idxCur = 0;
   idxOld = 0;
   dir = 1;
   LED_On (idxCur);                      /* switch on  first LED          */

   BUTTON_init();

   while (1);
}求分析

新人求教,急，

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