Microchip Technology MA160014 数据表

DS41412F-page 330

 2010-2012 Microchip Technology Inc.

#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 set up 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;

    }

}