PIC18F23K22-ESLASHML datasheet(326/496 Pages) MICROCHIP

326 / 496 page

PIC18(L)F2X/4XK22

DS41412C-page 326

Preliminary

 2010 Microchip Technology Inc.

EXAMPLE 19-4:

ROUTINE FOR CAPACITIVE TOUCH SWITCH

#include "p18cxxx.h"

#define COUNT 500

//@ 8MHz = 125uS.

#define DELAY for(i=0;i<COUNT;i++)

#define OPENSW 1000

//Un-pressed switch value

#define TRIP 300

//Difference between pressed

//and un-pressed switch

#define HYST 65

//amount to change

//from pressed to un-pressed

#define PRESSED 1

#define UNPRESSED 0

int main(void)

{

unsigned int Vread;

//storage for reading

unsigned int switchState;

int i;

//assume CTMU and A/D have been setup correctly

//see Example 25-1 for CTMU & A/D setup

setup();

CTMUCONHbits.CTMUEN = 1;

// Enable the CTMU

CTMUCONLbits.EDG1STAT = 0;

// Set Edge status bits to zero

CTMUCONLbits.EDG2STAT = 0;

CTMUCONHbits.IDISSEN = 1;

//drain charge on the circuit

DELAY;

//wait 125us

CTMUCONHbits.IDISSEN = 0;

//end drain of circuit

CTMUCONLbits.EDG1STAT = 1;

//Begin charging the circuit

//using CTMU current source

DELAY;

//wait for 125us

CTMUCONLbits.EDG1STAT = 0;

//Stop charging circuit

PIR1bits.ADIF = 0;

//make sure A/D Int not set

ADCON0bits.GO=1;

//and begin A/D conv.

while(!PIR1bits.ADIF);

//Wait for A/D convert complete

Vread = ADRES;

//Get the value from the A/D

if(Vread < OPENSW - TRIP)

{

switchState = PRESSED;

}

else if(Vread > OPENSW - TRIP + HYST)

{

switchState = UNPRESSED;

}

PIC18F23K22-E/ML Datasheet(PDF) 326 Page - Microchip Technology

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