如何在 c 中消除开关抖动？

Question

我在 MPLAB X IDE 上对 c 中的开关进行去抖动时遇到问题。我想做一个类似手电筒的东西，只有一个开关可以打开和关闭。有人可以帮助我吗？ 抱歉我的英语不好。

#define _XTAL_FREQ 4000000
#include <xc.h>
#include "pic16f1455.h"

/************************************************************
* Interrups/debouncing
*************************************************************/
/** Configuration ********************************************************/
// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.



// CONFIG1
#pragma config FOSC = INTOSC    // Oscillator Selection Bits (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON       // MCLR Pin Function Select (MCLR/VPP pin function is MCLR)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable (Brown-out Reset enabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = OFF       // Internal/External Switchover Mode (Internal/External Switchover Mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is disabled)



// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config CPUDIV = NOCLKDIV// CPU System Clock Selection Bit (NO CPU system divide)
#pragma config USBLSCLK = 48MHz // USB Low SPeed Clock Selection bit (System clock expects 48 MHz, FS/LS USB CLKENs divide-by is set to 8.)
#pragma config PLLMULT = 3x     // PLL Multipler Selection Bit (3x Output Frequency Selected)
#pragma config PLLEN = ENABLED  // PLL Enable Bit (3x or 4x PLL Enabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LPBOR = OFF      // Low-Power Brown Out Reset (Low-Power BOR is disabled)
#pragma config LVP = OFF        // Low-Voltage Programming Enable (High-voltage on MCLR/VPP must be used for programming)



char statusFlag = 0;



void main(void)
{
    TRISA = 0b00110000;            
    TRISC = 0b00000000;
    ANSELA = 0b00000000;
    ANSELC = 0b00000000;
    IOCAN = 0b00100000;
    INTCONbits.GIE = 1;           
    INTCONbits.IOCIE = 1;  

    
   PORTCbits.RC3 = 0;
    
    while(1)
    {
        if(statusFlag == 1)
        {
            if(PORTCbits.RC3 == 0)
            {
                PORTCbits.RC3 = 1;
            }
            else
            {
                PORTCbits.RC3 = 0;
            }
            statusFlag = 0;
        }
    }
}


void __interrupt() ISR(void)
{
    if(INTCONbits.IOCIF == 1)                       
    {
        INTCONbits.IOCIF = 0;
        if(IOCAF5 == 1)
        {
            IOCAF5 = 0;
            statusFlag = 1;
        }

    }
}

我用队列程序尝试了它，我希望它能够工作并完全消除开关抖动，但它只是有时有效，我想要每次都有效的东西。

Answer 1

对于最简单的去抖形式，然后创建一个循环定时器中断，每 5 毫秒左右触发一次。从 ISR 内部你需要类似的东西：

void timer_isr (void)
{
  uint8_t tmp;
  static uint8_t prev;
  tmp = gpio_port;

  if(tmp == prev)
  {
    debounced = tmp;
  }
  prev = tmp;
}

其中

debounced

在文件范围内声明为

static volatile uint8_t debounced=0;

。这一切都是在按下开关时高电平有效 = 1 的假设下进行的。

Answer 2

C 中消除按钮抖动的一个简单方法是等待一定的延迟，然后检查按钮是否仍然被按下。延迟越短，响应越快，但可靠性越差。尝试不同的延迟长度，看看哪种最适合您和您的手电筒。像这样的东西：

void __interrupt() ISR(void)
{
    if(INTCONbits.IOCIF == 1)                       
    {
        __delay_ms(100); // Wait for button to finish bouncing
        if(PORTAbits.RA5 == 0) // Check if button is still pressed
        {
            if(statusFlag == 1)
            {
                statusFlag = 0;
            }
            else
            {
                statusFlag = 1;
            }
        }
        IOCAbits.IOCAF5 = 0; // Reset interrupt bits
        INTCONbits.IOCIF = 0; // Reset interrupt bits
    }
}