电容式触摸按键技术详解

//******************************************************************************    
// Software License Agreement    
//    
// The software supplied herewith by Microchip Technology    
// Incorporated (the "Company") is intended and supplied to you, the    
// Company’s customer, for use solely and exclusively on Microchip    
// products. The software is owned by the Company and/or its supplier,    
// and is protected under applicable copyright laws. All rights are    
// reserved. Any use in violation of the foregoing restrictions may    
// subject the user to criminal sanctions under applicable laws, as    
// well as to civil liability for the breach of the terms and    
// conditions of this license.    
//    
// THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES,    
// WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED    
// TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A    
// PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT,    
// IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR    
// CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.    
//    
//******************************************************************************    
   
// *****************************************************************************    
// Filename:  Main727.c    
// Date: Dec. 13, 2007    
// Purpose: Illustrate the use of the Capacitive Sensing Module    
//  This program scans 16 pads on a PCB. Each pad is sensed by the Capacitive     
//  Sensing Module at a fixed interval.  The frequency of each pad at rest is averaged.l    
//  When a pad is touched, the frequency on the Cap. sensing module changes due to the     
//  extra capacitance from the finger.  The change in frequency is noted and the LEDs    

//  light up to indicate which button was pressed.    
// *****************************************************************************    
//    
//  Compiler:   Hi-Tech PIC-C v.9.60    
// *****************************************************************************    
   
#include    <pic.h>    
#include    "Cap_Sense.h"    
   
   
   
   
#define METHOD          4       // 1= Timer0 Base; 2= Timer2 Base; 3= WDT base; 4=WDT Sleep Base    
   
#if METHOD == 4    
__CONFIG(INTIO & WDTEN & PWRTEN & MCLRDIS & UNPROTECT);   
#else    
__CONFIG(INTIO & WDTDIS & PWRTEN & MCLRDIS & UNPROTECT);   
#endif    
   
/** Variables **/   
   
bank1 unsigned int  reading[NUM_BTTNS];     // current reading for each button    
bank1 unsigned int  average[NUM_BTTNS];     // running average for each button    
bank1 unsigned int  threshold;              // threshold value is req'd # counts decrease from avg    
unsigned char       index;                  // index value relates ea. button and scanning sequence    
   
bank2 unsigned int threshold128;            // Threshold of 1/128th = 1/128th of the average value    
bank2 unsigned int threshold64;             // ... used in computation of threshold variable    
bank2 unsigned int threshold32;             // ... threshold is a selection of the sum of these