PIC18F23K22-ESLASHML datasheet(322/496 Pages) MICROCHIP

322 / 496 page

PIC18(L)F2X/4XK22

DS41412C-page 322

Preliminary

 2010 Microchip Technology Inc.

EXAMPLE 19-2:

CURRENT CALIBRATION ROUTINE

#include "p18cxxx.h"

#define COUNT 500

//@ 8MHz = 125uS.

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

#define RCAL .027

//R value is 4200000 (4.2M)

//scaled so that result is in

//1/100th of uA

#define ADSCALE 1023

//for unsigned conversion 10 sig bits

#define ADREF 3.3

//Vdd connected to A/D Vr+

int main(void)

{

int i;

int j = 0;

//index for loop

unsigned int Vread = 0;

double VTot = 0;

float Vavg=0, Vcal=0, CTMUISrc = 0;

//float values stored for calcs

//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;

for(j=0;j<10;j++)

{

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

PIR1bits.ADIF = 0;

//Clear A/D Interrupt Flag

VTot += Vread;

//Add the reading to the total

}

Vavg = (float)(VTot/10.000);

//Average of 10 readings

Vcal = (float)(Vavg/ADSCALE*ADREF);

CTMUISrc = Vcal/RCAL;

//CTMUISrc is in 1/100ths of uA

}

PIC18F23K22-E/ML Datasheet(PDF) 322 Page - Microchip Technology

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