Help with Pic Delay Pulse code please

[Melanie]

I can't answer questions on your programmer as I don't have one.

Your CONFIG settings should match those preset into the program, but whether your programmer is actually programming them is another qustion.

If MCLR needs a pull-up, then the CONFIGS sure don't match (or yor PIC is broke)... it could be there's another tick-box in your software for your programmer that needs activating. My software for example has the ability to program the PIC and leave the CONFIGS untouched unless I've set it on another screen. This also means that GPIO4 could have OSC coming out of it instead of it being used for I/O.

Worst case scenario is I can send you my PIC, but it means you can't make changes if your programmer is misbehaving.

[g7jiq]

Hi Melanie,

Some very good news, I managed to get it sorted,
It works superb,

The problem I had was two fold,
The first one was the configs fuse settings, It now works without the 4k7 pullup resister on the MCLR pin. (just as you said)

It would then work in the breadboard fine but not in my circuit,

To cut a long story short,
When I lifted the output pin and dropped an led on it, it worked fine,

So.... I found that,

The pic's output drives an opto and led in series, with a 470 ohm to the 5v rail.
The pic also feeds an input to another pic, (which drives my lcd)
Somehow there wasnt enough current to drive the circuit even tho there should have been,
so I fitted another opto isolator as a buffer and this sorted it.

What a run around,

Many many thanks for all your help and patience, your a star...

Cheers
Dave...

[Archangel]

2 rules in this forum:
#1. Never doubt Melanie.
#2. Go back to Rule #1

[g7jiq]

I never doubted her in the first place,
I just couldn't see the wood for the trees....

[Chris Barron]

I never doubted her in the first place,
I just couldn't see the wood for the trees....

Out of interest Dave, did you try inverting the MCLRE config assignment ?

The only reason I suggested it may be a problem was because I had a similar problem once. Now that you mention whcih programmer you used I recall that was the same programmer I had when I had the problem. (Did you know you can upgrade the firmware of that thing to the latest version to make it cover more pics with more memory etc ? it's worth looking into.)

As for the led and the opto in series, you had a 470ohm resistor across 0.4V, which means the current limiting was in the order of I=V/R = 0.4/470 = 0.00085 A (850uA microamps)

That's not normally enough to drive anything requiring a strong switching signal, though most TTL circuits should cope.