- 您现在的位置：买卖IC网 > Sheet目录321 > DM164120-1 (Microchip Technology)BOARD DEMO PICKIT 2 LP COUNT
LPC Demo Board Lessons
3.2.6
Lesson 6: Switch Debouncing
Mechanical switches play an important and extensive role in practically every
computer, microprocessor and microcontroller application. Mechanical switches are
inexpensive, simple and reliable. In addition, switches can be very noisy. The apparent
noise is caused by the closing and opening action that seldom results in a clean
electrical transition. The connection makes and breaks several, perhaps even
hundreds, of times before the final switch state settles.
The problem is known as switch bounce. Some of the intermittent activity is due to the
switch contacts actually bouncing off each other. Imagine slapping two billiard balls
together. The hard non-resilient material doesn’t absorb the kinetic energy of motion.
Instead, the energy dissipates over time and friction in the bouncing action against the
forces push the billiard balls together. Hard metal switch contacts react in much the
same way. Also, switch contacts are not perfectly smooth. As the contacts move
against each other, the imperfections and impurities on the surfaces cause the
electrical connection to be interrupted. The result is switch bounce.
The consequences of uncorrected switch bounce can range from being just annoying
to catastrophic. For example, imagine advancing the TV channel, but instead of getting
the next channel, the selection skips one or two. This is a situation a designer should
strive to avoid.
Switch bounce has been a problem even before the earliest computers. The classic
solution involved filtering, such as through a resistor-capacitor circuit, or through
re-settable shift registers (see Figures 3-4 and 3-5). These methods are still effective
but they involve additional cost in material, installation and board real estate. Why
suffer the additional expense when software is free and program memory is abundant.
FIGURE 3-4:
FILTERING DEBOUNCE SOLUTION
+V
R2
R1
Filtered
Switch
SW
C 1
Output
FIGURE 3-5:
SHIFT REGISTER DEBOUNCE SOLUTION
+V
R1
D
Qn
Filtered
Switch
SW
CLK
CLR
Output
Debounce
Clock
? 2005 Microchip Technology Inc.
DS51556A-page 23
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
DM164120-3
BOARD DEMO PICKIT2 28-PIN
DM164120-5
BOARD DEMO PICKIT 2 64/80-PIN
DM164123
KIT MANAGEMENT SYSTEM PICDEM
DM180021
KIT STARTER MPLAB FOR PIC18F MCU
DM183022
BOARD DEMO PIC18FXX22 64/80TQFP
DM183032
BOARD EXPLORER PICDEM PIC18
DM240001
BOARD DEMO PIC24/DSPIC33/PIC32
DM240002
BOARD DEV EXPLORER 16 44-PIN
相关代理商/技术参数
DM164120-1
制造商:Microchip Technology Inc 功能描述:DEVELOPMENT TOOLS - PICKIT 2 LOW PIN COU
DM164120-2
功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 44-Pin Count Demo Brd RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM164120-3
功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 Count Demo Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM164120-4
功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 1 Dem Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM164120-4
制造商:Microchip Technology Inc 功能描述:PICkit 2 18-Pin Demo Board
DM164120-4/16F1827/PG164130
制造商:Microchip Technology Inc 功能描述:PICKIT PIC16F648A DEMO BOARD 制造商:Microchip Technology Inc 功能描述:KIT STARTER 18PIN F1 ENHANCED CORE 制造商:Microchip Technology Inc 功能描述:PICKIT, PIC16F648A, DEMO BOARD 制造商:Microchip Technology Inc 功能描述:PICKIT, PIC16F648A, 18 PIN, DEMO BOARD; Silicon Manufacturer:Microchip; Core Architecture:PIC; Core Sub-Architecture:PIC16; Silicon Core Number:PIC16F; Silicon Family Name:PIC16F18xx; Kit Contents:Demo Board, 2x Bare PCB Boards
DM164120-5
功能描述:开发板和工具包 - PIC / DSPIC PICkit 2 64 demoBoard RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM164123
功能描述:开发板和工具包 - PIC / DSPIC PICDEM Sys Mgmt Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压: