Stripboard JDM

I wasn't sure if this is the right place but...

I'm working on breadboarding the JDM (using the stripboard JDM page as a guide) and I noticed something peculiar. The JDM schematic shows a PIC16C84 and I have PIC16F628 from the Universal Controller card page. Excuse me while I demonstrate my ignorance - but how similar are these two? Should I be starting somewhere else? I'm reasonably certain that I need to program these before they will be suitable controllers but I could use a little advise.

I'm sorry I'm so totally clueless - I promise I'll get better.

I built the JDM and used it for quite a while. I found it to be a pig, mostly because it is built around a full RS-232 specification which means that you expect some fairly substantial voltage out of some of those pins. Unfortunately, a lot of very ordinary PCs' RS-232 ports are not built to a full RS-232 specification and do most definitely NOT give you the voltage you need to program them more than a few times. MY experience was that the JDM got very expensive in useless 16F628s very quickly.

This...

[users.tpg.com.au]

may shed some light on the JDM's problem and suggests a way to fix it. I'd want somebody like Simon or Vik to take a hard look at it first, though.

For my part, I'd suggest that if you have a few extra bucks you can save yourself a lot of waste if you just buy a good PIC programmer. Good ones start at about $50. I bought a MeLabs PIC programmer that uses my USB port. It cost $115 and was worth every penny. First off I don't have to crawl under my worktable to plug the thing in and secondly I don't have to unplug my comms card for Tommelise every time I want to program a PIC chip, either.

That's my two cents worth. You'll find that others here entertain very different experiences and will have very different advice.

Corey, the JDM programs 16f628s as well as others. The 16C84 is an earlier and I think smaller model. Read the instructions closely, I seem to remember something about a pin that was talked about that I had to figure out what to do with. Tying it low or high through a header, depending on whether you need to do other types of chips. Give another shout when you get to that or if you have other problems.

Yes, I'm one of those that have had a very different experience

I've been using a JDM programmer for perhaps 7 years, and I've never fried a single PIC after programming literally thousands of PICs. I'm not even sure quite how you'd do it. Prior to using a JDM programmer, I used a relatively expensive commercial programmer from Microchip, but it wasn't as good as the very cheap JDM programmer (except it had a ZIF socket which was nice).

The 16f628 is a distant descendant of the 16c84, but Microchip very nicely maintained the same pinouts over the years. However there is a small difference, and that is accounted for by moving a jumper. Since for reprap, you'll probably never program anything old, you can just hardwire the jumper. There are some details of the jumper (J2) on the wiki page.

I mostly do PIC programming from Windows using ic-prog, because it's pretty nice. The linux programmers also work well.

The serial port issue never used to be a problem because once upon a time people knew how to follow a spec, but there is a bit of a trend to make crappy serial ports these days. However in general I think you'll find all real PC serial ports (on-board, PCI, ISA, etc) will work. Laptop serial ports are sometimes not so good, and some cheap USB serial port dongles aren't good either.

In the not-too-distant future, there will hopefully also be a simpler and cheaper RepRap based PIC programmer, though it will require having a working RepRap in the first place for it to work.

***However in general I think you'll find all real PC serial ports (on-board, PCI, ISA, etc) will work.***

I can add to that that here in the US Dell Computer, otherwise a quite reputable firm uses crappy, non-spec RS232 ports even on expensive workstations like the one I have. Intel motherboards do the same thing.

Edited 1 time(s). Last edit at 03/14/2007 10:22AM by Forrest Higgs.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

Well, the beauty of my using a breadboard is that I can try out whatever. First I'm going to make the JDM - then I'll give Forrest's suggestion a shot. If I can figure it out. It looks pretty straightforward. I'll let you all know when I have something to show.

***First I'm going to make the JDM - then I'll give Forrest's suggestion a shot.***

Sounds like a plan. :-)

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

I have a bunch of Intel boards, and I've never run into that problem. Perhaps there's just something wrong with your JDM programmer (?).

I don't know about Dell because I avoid that stuff like the plague, but I would have thought they'd be using the same sort of serial chipsets as all the other major vendors.

Yeah, I always build everything on a breadboard to start with. It's a good way to start, but I find once you start using a breadboarded device too much like a real part, you end up getting loose connections or shorts that you don't normally get under prototyping conditions. They're sometimes a pain to track down and could potentially damage other components, so I always like to make a proper board if I want it to last.

I'm not 100% sure, but I think the extensions Forrest linked to only apply to a newer family of PICs that we're not using. I program lots of PICs under exactly the conditons they say cause the problem, and it has never happened. But I don't use that family of PICs, so I'm pretty sure that's the important factor... But it probably wouldn't hurt to try it anyway

***Perhaps there's just something wrong with your JDM programmer (?).***

I don't see what it could have been. It's not like that's a very complicated circuit. In any case I dumped it many moons ago. I use the MeLabs programmer for all my work now.

Yeah, probably not a bad move. Compared to the time to build the JDM programmer, the cost isn't really that high anyway.

I have a Pic start 2 from Micro Chip it runs for about $45.00 us. I have to make an interface board to program 12f628 chips. It can program directly to the board they are on. since I am on the subject of USB I thought you have to have a license to produce a componant with a interface on it? I do not know if there is a open source part of this or any thing if you make it on your own and not in production?

Interesting, I never heard about needing a license to incorporate a USB connection into a system. It wouldn't surprise me, though. I'm using Microchip PIC 18F4610 which has USB support on-chip and that the compiler I'm using for the firmware has .ocx and .dll files so that you can talk to it via USB ports from your Wintel PC.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

I think for PICs that support USB, the processor cost includes a small license fee, so we don't need to worry about it.

Corey,

I love the smiley face avatar

Lol, I just noticed his breadboard -was- the smiley

I was just wondering if you were still having problems programming PICs. I've been reading a lot about programming them and now know quite a bit as far as the 16f628 and similar pics go. The voltages and the sequence in which they are applied are key. Then it's just 2 lines, the clock and data and the data format for making it do what you tell it. Thats what makes ICSP (In Circuit Serial Programming) so popular, not a lot of wires to mess with.

excellent. i know one of the things we really want to do is get a programmer board integrated with the project... perhaps a power/comms/programmer board? or maybe even just a separate programmer board that you plug into the token ring.

have you tried building the stripboard jdm?

I did build the stripboard JDM, slightly modified. I used a 12 volt zener and a couple extra diodes (.6v x2 = 1.2) and 12 + 1.2 is right around 13 It had to be referenced to the same potential as the 5v zener since I was providing a seperate voltag rather than adding to the 5v which is still required. That was fairly trivial but I wasn't sure if something else would be a problem with my doing that. I gave up the EE path and went CS a long time ago. It worked for me first time and I've used it 5 or 6 times since then flawlessly. I'm looking into built in programmer. Simon got me interested and I have some ideas about what I need to do to create one. I wanted to get my controller working first and I've done that now, so I'll be experimenting. I'm not sure whether I should try integrating the commands into the controller first or just make the programming functions work wired to do some basic stuff like erase, program 16 bytes, etc triggered by switches for example.

neato. thanks for the update and please keep posting back. very interesting.