18F4431 and Melabs USB programmer ?

[mister_e]

PICKIT 2 usually works a treat. But yeah, if it's a silicon related issue, you may end up with the same results. I think Pickit 2 allow to play with MCLR voltage ...

What's your Vdd voltage?

Can you read the Silicon revision of your PIC?

[Darrel Taylor]

I thought trying a new 4431 here might shed some answers ... but I don't think this will help a bit.

I've programmed it here with both the U2 and PICkit2 programmers.
It works everytime no matter what I try.

Unfortunately, I only have one 4431 in my bin.

The Device ID/REV in my chip is 0882. Is yours the same?
(meProg | Program | Get Target Information)

If I could be sure that the U2 programmer works with no problems I'd buy it, or the PICKIT 2

I like the PICkit2 better, but I have several programming adapters and ICSP cables wired for meLabs 10-pin format. So I usually end up using the U2. The PICkit2 has a 6-pin connector and I'm too lazy to make new cables.

[AndrewC]

If I read the device I get

Device 0000- 0882
Config 0000- cf00 3f0f 9d3c 0085 c00f e00f 400f
Code all FFFF

Vdd is a nad over 5V.

Got some advice from Melabs and changed the ProgTimes - one off improvement and then none of the pesky things will program.

Went back to the original ProgTimes and now back to flakey results - some good some bad units.
However, they now all program on my X2 board either with the board Vdd or the USB prog Vdd. so the X2 board has a cap right up against Vdd/Vss so I tried that on my ZIF adapter - no improvement.

Verdict - beats me At least I've got a work around, that works tonight anyway. I'm wondering if Mister_E's cable length might be the clue ? I'll need to see if I can make a Melabs 10pin cable and try that.

Andrew

[tenaja]

I've programmed a LOT of 18F2331's, all of them with MELabs programmers (I have 3 versions; epic, serial and USB). Here is what I've found:

For ICSP I put in a jumper to disconnect the programming power supply from the rest of the board. That way only the PIC is powered when the programmer is in use. When I unplug the cable, the jumper is put on and the pic gets power from the board.

Today I was programming some DIPs repeatedly, using the MELabs programmer and a zif adaptor. I had to add a jumper to the adaptor, as shown on their web site. (I think my adaptor was almost 10 years old!) Because the chip was being used on a development board, I didn't have the luxury of putting on a jumper. I was not surprised to find the chip wouldn't program ICSP.

A couple months ago I did run in to a couple bad 18F2331 PICs. Some new code worked perfectly on several chips, but on several it did not. I was thankful that I didn't get the faulty chips for the first one, or I would have suspected my code!