My Port B does not want to work

Slick05 · Joined: 05 Feb 2005 Posts: 14

For some reason on the PIC18F458, when I set PORT B to output and output 0xFF onto LEDs they all light up except B5,B6,and B7. However all of the pins on PORT B work fine as input.

I think I just thought of something, maybe PORT B5,6,7 need a zero in order to light the LEDs, I will try it out. I have tried writing

pullups_b(true)

however, that only keeps PORTB high, which does me no good. But I have two pics and both of them do the same thing, so I know for sure I am doing something incorrect.

So if anyone could explain the problem that would great. It may also be the reason why I cant my program to interrupt when there is a change on PORT B.

Anyways easy programming...

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Post a small test program. They only need a zero if you are sinking the current. PortB Pullups are for inputs, not outputs.

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

The functionality for many pins of the PIC processors can be configured from a choice of possible functions. Very likely the pins RB5, RB6 and RB7 in your setup are not configured for digital I/O but for another purpose.

RB5:
Is default configured for Low Voltage In-Circuit-Serial-Programming (ICSP). Add NOLVP to your #fuses statement if you want to use this pin for I/O. (and make sure to have removed any LVP option from this same line....)

RB6/RB7:
May be used for an In-Circuit Debugger.
Add NODEBUG to your #fuses statement (and remove any DEBUG option from this same line....)
Also check this option is not activated by a '#device ICD=true' statement in your code.