c++ - int8_t 的增量计数

Question

我正在研究 cortex m0。我想增加一个声明为 int8_t 的变量的计数，但在显示输出时它非常不稳定。代码:

//
// Smpl_7seg_keypad
//
// Input:  3x3 keypad (input = 1~9 when key is pressed, =0 when key is not pressed
// Output: 7-segment LEDs
//
#include <stdio.h>                                                                                                           
#include "NUC1xx.h"
#include "DrvSYS.h"
#include "Seven_Segment.h"
#include "scankey.h"
#include "NUC1xx-LB_002\LCD_Driver.h"


int32_t main (void)
{
int8_t number;
char a[]={'0'};
int count=0;
char arr[]="    ";

UNLOCKREG();
  DrvSYS_Open(48000000);
LOCKREG();

OpenKeyPad();   
Initial_panel();
clr_all_panel();
//print_lcd(0, "Msrit");
sprintf(arr,"%d",count);
print_lcd(0,arr);
while(1)
{
  number = Scankey(); 
    //a[0]=48+number;
    if(number ==1)
    {
        clr_all_panel();
        count++;
        //print_lcd(0,"\(\\__/\)");
        //print_lcd(1,"\(='.'=\)");
        //print_lcd(2,"\(\"\)_\(\"\)");
        sprintf(arr,"%d",count);
        print_lcd(0,arr);


    }
    else if(number==2)
    {
        clr_all_panel();
        count--;
        //print_lcd(0," O");
        //print_lcd(1,"\/|\\");
        //print_lcd(2,"\/ \\");
        sprintf(arr,"%d",count);
        print_lcd(1,arr);

    }
    //print_lcd(1, a); 
    // scan keypad to get a number (1~9)
    show_seven_segment(1,number); // display number on 7-segment LEDs
    DrvSYS_Delay(5000);           // delay time for keeping 7-segment display 
    close_seven_segment();        // turn off 7-segment LEDs                                 
}

例如输出为: 12,28,28,29,41

我需要对代码进行哪些更改才能使计数变量正常递增？

Answer 1

增量本身很好。问题是您正在紧密循环中检查 Scankey()。无论您松开按钮的速度有多快，循环都会设法执行多次，使计数器增加一以上。

在再次递增计数器之前，您需要等待按钮被释放。一种方法是保留您从 Scankey() 获得的最新值，并且仅在 Scankey()< 的输出时输入 if 序列 更改:

int8_t prev_number = 0;
...
while(1) {
  number = Scankey();
  if (number != prev_number) {
    if(number == 1) {
      clr_all_panel();
      ...
    } else if (...) {
      ...
    }
  }
  prev_number = number;
  ...
}

另请阅读 debouncing .