Microchip Technology MCU PIC PIC18F87K22-I/PTRSL TQFP-80 MCP PIC18F87K22-I/PTRSL Data Sheet
Product codes
PIC18F87K22-I/PTRSL
2009-2011 Microchip Technology Inc.
DS39960D-page 397
PIC18F87K22 FAMILY
EXAMPLE 27-4:
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
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;
}
}