PICs and Weak pull-ups

That's wrong, I must've connected wrong, since it works fine with 10K resistors. It's just without - it's as if the weak pull-ups don't work (the global setting is 0, but all pull-ups 1 on power. I set the global setting to 1).

Ah well, I'll just leave them off and do it myself!

The plot thickens... I just made a change to my code (unrelated) and re-programmed it. Now, with 10K resistors, it doesn't seem to work with pull-ups turn on or off!

I'll do some further digging after breakfast - it's probably user error!!

Danny T

I only recently started learning to program PICs myself and haven't yet used the pull-ups but I read something today which explains why I thought I'd zapped RA4 on a 16F84A - LED wouldn't light. It may be of help in the future if you don't already know. I'm not sure if it applies to other PIC though.

The 16F628 has it's I/O pins split across two ports, PortA and PortB, these have quite different properties, and it's important to understand these differences or things don't always work as you expect!. Firstly PortB, this is pretty straightforward, although some of the pins can be used by various of the built-in hardware, as a normal port all pins can be inputs or outputs. PortA is a little less straightforward, all pins can be used as inputs, but RA5 can only be used as an input, and RA4 has an 'open-collector' output stage, this means it requires a 'pull up' resistor to function as a 'normal' output - it can 'sink' current, but can't 'source' it. RA4 in the

Cheers,

Andrew.