Expansion Module #1 - Standalone Project

[a2dconverter]

I had a spare Atari Expansion module so I built a standalone Atari module... don't know why but it was fun!

 

I originally posted this in the ATARI 2600 forum... its probably more useful here... 

 

Hopefully some of the info helps somebody else...

 

Seeya

 

Joe

 

 

 

 

Standalone EXM1.pdf

 

 

 

Edited October 29, 2020 by a2dconverter

[Itchy Scratchy]

So the CPU on the expansion module originally gets the 3.58 from the Colecovision?

All you had to do is supply a crystal and connect it to 5v and ground.

 

Interesting that this is basically an Atari 2600 without an output for the audio/video.  Power and CPU timing.

No wonder Coleco was sued.

Then again if it was all off the shelf parts and no stealing code then you have to wonder.  Maybe it was cheaper to settle.

 

This may also be why the Intellivision expansion never came out.  In that case they would have to include some version of a GROM and EXEC.

 

The adapters seem to stop when the next generation systems came out I think because of the BIOS's involved.

[Falonn]

This is awesome.  Nice work!  It's surprising how few components it takes to remove the rest of the Colecovision from the equation.

 

It would be cool to see the whole thing put on a small PCB with a card-edge connector to slot right into the back of the expansion module.  Then you would have a "no cut" version that could be assembled/sold as a single plug-and-play unit.

[imstarryeyed]

Oh wow what a great project I always wanted to know what it would take.  I totally have to do this mod to the 1 of the 2 units I have.

[Ruggers Customs]

Excellent work!

[NIAD]

Very nice and clean mod.

 

I think it was phattyboombatty who was the first one to perform this mod back in 2012. He stated that his would still work when connected to a CV or ADAM... if one still wanted to use it that way.

 

[Ruggers Customs]

8 hours ago, NIAD said:

Very nice and clean mod.

 

I think it was phattyboombatty who was the first one to perform this mod back in 2012. He stated that his would still work when connected to a CV or ADAM... if one still wanted to use it that way.

 

That's just beautiful.  I had a request about a year or so ago to do that for a friend but he ended up sending me a 7800 instead for a no cut mod and a UAV mod. 

 

I've been wanting to do something like this with a UAV mod even though that might be overkill.

[Supergun]

On 11/1/2020 at 1:39 PM, NIAD said:

“...I think it was phattyboombatty who was the first one to perform this mod back in 2012...”

 

Not to take away from him and/or the others here whom have done these mods, as they are very cool indeed, but for the record, this was first done way back in the late 90’s. Back during the rec.games.video / classic video game nexus era.

[NIAD]

10 hours ago, Supergun said:

Not to take away from him and/or the others here whom have done these mods, as they are very cool indeed, but for the record, this was first done way back in the late 90’s. Back during the rec.games.video / classic video game nexus era.

Well, if it didn’t happen on AtariAge, it didn’t happen!!!!

 

Just kidding.

 

i spent a lot of time in that Newsgroup.

[Falonn]

I gave building this a shot, but had some trouble.  The video from expansion #1 through my ColecoVision is just fine, but through the mod, it shows up very dark.  Only the brightest colors just barely register on the screen.  Since the "external video" pin runs straight to the place people usually tap for the composite video mod in their CV, I'm guessing it's just a weak signal that needs a bit of amplification.  I tried cobbling something together from parts I had on hand and was able to get something too-bright to show up, at which point I decided to stop fiddling with it for now.

 

Instead of drilling holes and adding stuff to the expansion module itself, I wanted to try making a little card-edge adapter that did all the same stuff (like I'd mentioned up in the #3 post).  It turned out pretty cool and fit perfectly on the first try:

 

 

Don't mind the bodge wire on the ground pin; that was for debugging.   All the parts are through-hole, so it goes together in just a few minutes with a soldering iron.

 

I did change a couple things in the design.  I can't imagine any of them are responsible for it not working, but here's the list:

1. It uses HDTV1080P's Mean Well power supply, which already has all the exact voltage levels necessary.  No voltage regulators needed.
2. I included the same power filtering capacitor+inductor scheme from the ColecoVision board.  This was more of a "better safe than sorry" measure.  It's a long power cord, so having some local filtering made me feel better.
3. I added some debouncing to the reset switch.  I was going to use the same scheme from the CV board again, but they've got an elaborate pulse-generator thing.  I decided to meet in the middle and add something but keep it simple.

 

 

Anyhoo, once I saw that there was still design work to be done, I decided it exceeded the amount of time I had for a simple board layout exercise (and eventual 3D printed case design) and am going to leave it unfinished.  I just put all the files on GitHub with a public domain license if anyone else wants to pick the project up from here.

[digress]

cool. you could sell over hundred of these once working. 

[Falonn]

In a turn-key little box that anyone can just click onto the back of their expansion module, at around $10 in parts wholesale (leaving plenty of room for a healthy margin), I think you might be right!

 

Hopefully that will be a big enough carrot to have someone else pick it up.  I know I'd be first in line to buy one if someone else finished it.

[Amigaman]

This information is greatly appreciated.  I would like to build an interface (pass thru) to allow the use of this module with a Commodore 64.