Long time - no c - Programmer Dongle Project

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eskoilola
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#1
Posted by eskoilola: Tue. Sep 15, 2009 - 10:51 PM
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Hi everyone !

It was a while when I last wrote to this forum. This does not mean that I would have ignored it - I have not just written here.

I finally got fed up with my STK200 dongle and especially the very short cable with it. I have my "desktop" computer under my table and would like to have the project on top of it (the table not the computer). With the 10 pin cable this is not possible so I have had a small side table (beer box) to get a good aim onto the project in hands.

So I have been spending some time in reading this forum and especially on posts dealing with dongles. The net result was a Parallel Port Programmer Dongle.
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(Click on the image to reach the project site)

The dongle is 3-5 volt compatibel and it is fully compliant with the old STK200 dongle with the exception of a missing /LED signal. I have never had any use for it and since the HC125 only offers 4 buffers I simply left it out.

The 10 pin pin header had to go. It is all too easy to connect it the wrong way around and the cable is not designed for repeated push-in/pull-out operations. And it is short.

So I made use for the SMD RJ45 connectors I have sitting in my shelf. Yeah, I have some thousands of these.

I am sure there is a recommendation for pinning this connector for programming purposes. However, I decided to make the pinning such that the MOSI, MISO, SCK nad /RESET signals can be connected on the project without making any criss-cross jumper design. Just four parallel lines coming out of the MCU and going in into the connector. Same applies to the VCC and GND lines - well - at least with Mega32 of which I have a good supply of.

Another reason for choosing the RJ45 connector is the supply of suitable cables. It is endless. These are much more available than the 10 pin flat cables.


Yet another home page

Tags:

AVR Microcontrollers, megaAVR and tinyAVR
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zbaird
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Posted by zbaird: Tue. Sep 15, 2009 - 11:15 PM
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Esko! How nice to hear from you, and see your little friend Britney, too!

Nice project - we'll have to see if it gets Nard's seal of approval. I certainly agree about the cable length problem.

Chuck Baird

"I wish I were dumber so I could be more certain about my opinions. It looks fun." -- Scott Adams

http://www.cbaird.org

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Plons
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Posted by Plons: Tue. Sep 15, 2009 - 11:15 PM
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Welcome back, Esko !
You could have saved yourself the trouble of designing a PCB for it: see the webpage in my signature :)

Cheers

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Plons
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Posted by Plons: Tue. Sep 15, 2009 - 11:16 PM
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Speedy Scooby :lol:

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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RickB
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Posted by RickB: Tue. Sep 15, 2009 - 11:17 PM
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Where on earth did the symbol for T1 come from? Looks like the result of an unholy union between a jfet, a unijunction and a bipolar. :D I think I have it figured out, but it will drive newbies to drink.

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eskoilola
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Posted by eskoilola: Tue. Sep 15, 2009 - 11:32 PM
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RickB wrote:
Where on earth did the symbol for T1 come from? Looks like the result of an unholy union between a fet, a unijunction and a bipolar. I think I have it figured out, but it will drive newbies to drink.

LOL ;)
I have to admit it ... the design is courtesy of ... myself.

Plons wrote:
You could have saved yourself the trouble of designing a PCB for it: see the webpage in my signature Smile

Actually I got most of the ideas from Your articles. Especially the slew rate limiting. I have always wondered why this thing is so sensitive to cable length - I followed Your track and took a good look into the SCK line. This version has no ringing in it anymore. I can safely use a 5 meter cable.

The reason I did not use Your layout was the available components. It has been several years since I had to buy any electronic components. I have "inherited" a few component stocks of companies gone bankcropsy so if I do my designing well - I don't need to buy any more electronics stuff during the next 10 years or so.


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Guillem Planisi
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Posted by Guillem Planisi: Wed. Sep 16, 2009 - 08:29 PM
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I believe you when you say that it works well, but I don't need anybody to tell me that your PCB layout rocks. Neat, componens well distributed, and round corners!!! I'm tired to see autorouted nasty (and troublesome) boards, enough to enjoy those that have some different and well done details.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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eskoilola
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Posted by eskoilola: Thu. Sep 17, 2009 - 02:51 AM
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Thanks for the kind words.

As I am an oldish sort of a man - someone would say "sandwich short of a picnic" - I may put effort and time on seemingly useless features like how it looks and that it is easy to build with my wobbly hands.

I have only recently learned that the way the traces connected to SMD pads is nothing but irrelevant. Since I don't have the opportunity to use a solder mask the solder tends to creep along the tracks and when it does that it unbalances the component floating on top of the solder if the traces are not connected the right way.

If - and only if - the traces are connected correctly the components will straighten themselves when the board is heated.

If You have the solder mask then all this does not apply. The solder is jailed in the square pads - it does not creep anywhere no matter how the traces are connected.


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eskoilola
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Posted by eskoilola: Mon. Nov 16, 2009 - 02:07 AM
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The dongle is now officially tested.

I used a standard (CAT5) RJ45 cable of about 3 meters length. No problems - works like a charm (with a 3 volt system).

I am very pleased with this tiny thing.


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svofski
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Posted by svofski: Mon. Nov 16, 2009 - 07:44 PM
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I would tin all those exposed tracks too. Unprotected, they're going to rot in just a couple years. And what everybody else said, again: very clean layout that's a pleasure to look at.

The Dark Boxes are coming.

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