bulding a jdm programmer

[spirosd]

Hello all,

I am building a jdm type programmer and plan to implement the attached schematic (found on the pikdev web site). Would appreciate some help in clarifying a couple of points.

I do not have a bc547b npn transistor, but do have 2n2222a. Can I substitute?

On the schematic between D4 and D3 there is a resistor '0 to 10K' :? not sure how to interpret that, any resistor value between no resistor to 10K?

Thanks
Spiros

 

[MikeHibbett]

Hum.. thats new to me. Haven't seen a resistor there before.

I used this one:

**broken link removed**

One thing to bear in mind: It works, mostly. I built a version on veroboard and it worked fine. I still use it, on several different PC's and laptops. So I thought I would build a 'proper pcb'. It didn't work.

I'm rather lazy with this analogue stuff so didn't bother to debug the problem; I at least have a version that works. All I can say is try it and see.

I build *lots* of pic circuits and really should invest in a decent programmer but I'm just to tight with my cash )

Nigel is a wizz with this stuff, maybe he will comment...

Mike.

 

[MikeHibbett]

Oh and to answer your first question, probably it is.

The 'B' variant of that transistor has a fairly low gain ( lower than the 'C' variant ) I cannot see any reason for that choice, but you wont destroy your pic trying it.

I use the JDM programmer with a wide range of pics, including the 18F2420 family and 16f877/16f877A. I think I had trouble with the 12F629 though.

M.

 

[spirosd]

One thing to bear in mind: It works, mostly. I built a version on veroboard and it worked fine. I still use it, on several different PC's and laptops. So I thought I would build a 'proper pcb'. It didn't work.
Mike.

Ouch ... that is not fair! "...Just when you thought you were safe ..." type of situation. Thanks for the heads up!

On the site that I took the circuit from, there is a mention about a problem when using a jdm (version 2??)with pics that have MCLR_OFF and INTOSC fuses enabled (see **broken link removed**). Apparently the circuit that I posted does not suffer from this.

Thanks for your help.
Spiros

 

[MikeHibbett]

>On the site that I took the circuit from, there is a mention about a problem when using a jdm (version 2??)with pics that have MCLR_OFF and INTOSC fuses enabled

Interesting, thanks for the tip.

The PIC is a fairly robust device family though. I have abused several with my rogue programming hardware with no damage.

I still smart at the memory of trying to program a hitachi 16 bit micro. Blood thing with glow if programmed incorrectly. cost me a fortune.

In my experience to date nothing beats the AVR micros. The programmer is a wire lead to a PC's parallel port and it never fails. IF only they had all the flavors that microchip have )

 

[eblc1388]

Hi spirosd,

Just build it and test it for fun. It will program a lot of PICs if it works. Much depends on the voltage/current of the serial port. In this case old PC is much better than Laptops.

Sooner or later you will find the JDM won't program certain PICs(in my case the 16F88 and the 18F4455) and you will start to think and build your second PIC programmer.

However, the JDM did allow me to program the firmware into a 16F877 as needed initially for the ICD2 and it sit lonely on my bench ever since.

 

[Nigel Goodwin]

Nigel is a wizz with this stuff, maybe he will comment...

I've always kept well clear of the JDM programmer, it's probably the hardest to get working, due to it's excessive demands on the serial port handshake lines. It's not really a 'serial port' programmer at all, it simply 'wiggles' the handshake lines, just as parallel port programmers do on the parallel port lines.

It's a very clever minimal design, but because of that it's troublesome, and is the main reason that WinPicProg does not support serial port connected programmers (which wouldn't take much effort to add).

 

[spirosd]

Thank you all for your comments.

From what has been indicated, whilst a great minimal programmer, better to think about a parallel port design or even icd2.

Cheers
Spiros

 

[panic mode]

imho nigel is right as always. i've built few of them. two have been confirmed to work fine but not on any of my computers. resistor 0-10k that is added betwenn D3 and D4 doesn't really do any good. someone tought this would help protect something (com port or D4) when RTS is positive (short to GND through D4). the fact is that com ports are current limited and according to spec must tolerate short circuits.

 

[akg]

imho nigel is right as always. i've built few of them. two have been confirmed to work fine but not on any of my computers. resistor 0-10k that is added betwenn D3 and D4 doesn't really do any good. someone tought this would help protect something (com port or D4) when RTS is positive (short to GND through D4). the fact is that com ports are current limited and according to spec must tolerate short circuits.

then i'm lucky .. , i got it work in first try

 

[davesaudio]

IMHO
Much of the difference in results can be attributed to:
typically JDMs work better with desktops than laptops
the older the better, the less power managment the better.
Older OS- 95 98 ME less trouble than adding dlls for 2000 and XP.