18F4431 and Melabs USB programmer ?

[AndrewC]

"If you have 2 Vdd, then you use 2 0.1+10uF. PGM pin load to gnd with <10k."

Not sure what you mean - on the Melabs USB programmer there is only one Vdd supplied, i've already got a 0.1uF across that on the programmer board. If I try programming it in-situ on the Melabs X2 protoboard I can use it's own Vdd and it also has 0.1uF Vdd-Vss next to the PIC. Where would you add 10uF ?

I've tried tying RB5/PGM to ground with 10k, perhaps I'll try something smaller.

MCLR is going to 13.2V

Spacing to programmer - I've seen some posts pointing at this. I'm using the short cable supplied by Melabs (<1" ?). I can try making a longer one

My biggest headache is "is it my programmer or my PICS ?". If I could be sure that the U2 programmer works with no problems I'd buy it, or the PICKIT 2, but no answer from MELABS yet. I'll email them again in case they overlooked my first three emails.

Micro chip pointed at the same note the Darrel posted - try playing with different Vdd values but could not tell me what to try and Vdd is not adjustable (to my knowledge) on the Melabs programmer. They didn't seem to buy in to my suggestion that 60% of the PICS they sent me were cxxp and they should give me some new ones. Of course I only bought 5 so I'm not very high up on their priority list

What alternatives would you recommend to using the ICSP serial type programmers ?

[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!