Why does my PORTC change on its own?

[kyru27]

I've the following code:

#include "p18F4620.h"
 
 
#pragma config XINST=OFF
#pragma config OSC=INTIO67
 


 void main (void)
{

char tecla;

TRISC=0xAB;	

PORTC=0x40;

Nop();

if (PORTCbits.RC5==1)
{
tecla=2;
}

if (PORTCbits.RC3==1)
{
tecla=0;
}

if (PORTCbits.RC1==1)
{
tecla=8;
}

if (PORTCbits.RC0==1)
{
tecla=5;
}


	 
}

The problem is that with the register PORTC changes its value where it has their inputs from 0 to 1 seemingly as it feels like, despite the inputs being 0 all the time and having 0 measuring it with a polimeter.

I've also checked that if I kept measuring the input and GND continuosly the changes on this input are done right (it doesn't change as long as I don't make it to change). Anyone has an idea what this would be equivalent to?

Regards.

 

[hexreader]

Do you have a pull-down resistor on each input, or have you left the inputs floating when no switch is pressed?

A floating input is likely to pick up mains hum, which would appear as a randomly changing input in your code.

 

[Ian Rogers]

When using single pins you'll find that " LATCbits.LATC2 = 1;", instead of "PORTC = 0x40;", will be more reliable.... In the datasheet look for "READ/MODIFY/WRITE"

You may need LATCbits.LATC4 and 6 aswell.