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jedimatt42

32k expansion for the side port - released

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YES!! A new 32k memory expansion for side port! If we add floppy controller (with HxC) to this memory expansion we have CF7+ solution!

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If this becomes reality, be nice if it had a case available. :grin:

Far too many of these projects are allowed to lay neked among our legacy peripherals. Must be a new millennium thing. :lol:

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Any updates on this cool little project?

 

/putting the cart before the horse mode ON

An off-the-shelf box would be nice, but with all these 3D printed object out there, I'd love to see a case eventually made for this with a little 'STYLE'. Maybe even an inset where a person could attach a piece of aluminum trim to match the TI's case? Who knows, once the dimensions are known, maybe even a competition to see who could design the coolest looking enclosure?

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The problem with these hobby projects getting 'style', is it is rare to find someone who's hobby has all of those ingredients. And then, my personal tastes will not be the same as others...

 

I actually love the look of a circuit board... I probably have ever since the first time I took my TI apart, from curiosity. I'd love to take on 3-d printing, but then you'd have to wait about 5 years for me to finish this... I haven't been able to get the hang of any 3-d modelling software since "Imagine" for the Amiga. But If someone with style wants to hit this with a can of magic, then I would welcome that. Of course, the hardware needs to be working first.

 

On the progress side, I haven't had success making the prototype work without the buffers. The behavior is very strange. I wish I understood oscilloscopes better.

 

I sent two pcboard layouts to OSHPark yesterday.

  • something like the pi-cobbler t-shaped ribbon cable to breadboard, to make working on the side port with a breadboard more tolerable.
  • a layout for the circuit I did get to work, with the buffer chips and all that. It is something like 4.25"w x 3.25"h.
If this board works, I'll open source it, but it won't be the final version that I intend to assemble. I still want to try a couple other layout patterns...

 

Here is what I sent off to OSHPark:

post-42954-0-53491400-1468820870_thumb.jpg

 

Now I need to remember who sells those 'give the foot the boot' ribbon cables for the side port, for my prototyping work. Oh, the pinouts on my protoboard side are reversed for the top of the sidecar. It was just easier that way.

 

Oh, and here is the candidate box, I would like the 32k to fit in for my own personal taste:

post-42954-0-94109600-1468821200_thumb.jpg

( never mind the stuff inside, that's just some Amiga tom-foolery )

 

[email protected]

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Now I need to remember who sells those 'give the foot the boot' ribbon cables for the side port, for my prototyping work.

 

 

You want to go << HERE >> as it's the cheapest option and it's from the same exact place as the more expensive website. It even has the same stock number.

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I shall not ignore the Amiga stuff... I like the cut of your jib.

I need to take a look and see if that PicoPSU had -5v, it might be applicable to the TI if it does.

 

I got bored on my last business trip and ended up winning an ebay PAL Amiga 1200. So I adapted this ATX supply. I used the crimp on pin tips for male DB25 connectors instead of bothering with some ATX socket harness.

 

BITD my A1000 had a power switch on the computer, my PC before that had a power switch on the computer, and my TI had a power switch on the computer. I was a little astonished that the A1200 did not.

 

That reminds me, I need to add a switch to the final pcboard layout for this 32K expansion. If i figure the pass thru layout, i want to have the externally supplied +5V feed the +5V pin on the outgoing connector, instead of what the TI supplies, as the TI output is limited to what the speech board needs.

 

[email protected]

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I was going to use a PicoPSU in the TI, I just never got a round tuit. As I recall, to be ATX-compliant is has to provide -5VDC.

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I was going to use a PicoPSU in the TI, I just never got a round tuit. As I recall, to be ATX-compliant is has to provide -5VDC.

 

The AT 20 pin spec requires -5VDC, but the ATX 24 pin spec denotes -5VDC as optional, which means ATX motherboards probably don't use it.

 

But the ATX PicoPSU I have had a 20 pin connector... which gives me hope that it might supply the -5VDC... easy enough to test... I just need a moment without laziness... :)

 

[email protected]

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I just went hunting through the manuals on the Mini-Box site--none of the PicoPSU variants I looked at had the -5V. I looked at the 120 (with 20-pin connector) and the 150 and 160 (with 24). I also looked at the Yoosoo equivalents, they don't have the -5V rail either.

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jedimatt42, on 07 Jul 2016 - 07:06 AM, said:

I gave it a shot today without the buffers, but it behaved very badly... manually, not connected to the TI, I can walk through the range of values A0-A2 with memen grounded, and get the CS output I want.. But connected to the 4a, it just seems to respond to all address ranges.

 

Anyway, I'll have to strip it down, and try again. I may try just buffering A0-A2 two see if that fixes the selection.

 

I'm interested in being able to run with 3 less chips.. not so much because of the buffer chips cost, but because the pcboard can get to be significantly cheaper the smaller it is.

 

Edit: ( I found the TI-99/4a Console Technical Data pdf on mainbyte... A Big thanks to the owner of that site! )

 

[email protected]

 

Matt, have you had a chance to progress this? I've knocked up the circuit on a breadboard with no buffers and it works OK**. Just the LS138, LS21 and the 62256 RAM. LS21 pin 6 is connected to the RAM /OE and /CS. The LS21 should be able to directly drive a small LED (with current limiting resistor) as well.

 

(** Frustrating to start with. My console has 32K 16-bit internal RAM running with no wait states, and a switch to disable. But the switch disabled the RAM but didn't disable the 0 wait states when accessing the 32K RAM area. So with the breadboard RAM circuit attached, it was somehow reading the address back as data. For example, stepping through the bytes from address >A000 using EasyBug would give the data >A0, >01, >A0, >03, >A0, >05 and so on. Very confusing. Had to rewire the switch so it gave the normal wait states as well when internal RAM disabled.)

 

Stuart.

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Stuart,

 

I'm not surprised that you got it to work... for so many reasons, but also cause you were right, the stuff is already buffered on the side-port.

 

Question: did you externally power things, or take the power off of the console?

 

Tomorrow I'll share the schematic I was trying without the buffers. In the meantime I had a couple boards printed to test, and those just arrived today.

Mem boards that are wired for the buffers, although in theory I could jumper them instead of installing the chips to test skipping the buffers..

 

And something to help keep my sanity on the bread-board.

 

post-42954-0-24479200-1469682664_thumb.jpg

 

post-42954-0-94835500-1469682797_thumb.jpg

 

post-42954-0-26612100-1469682811_thumb.jpg

 

I have the labelling wrong, as I didn't consider the pre-fab extension cable.. I also have the pin spacing on the edge card wrong, but am able to 'compress' the pins on the connectors I have and make it work. :)

I'll use a sticker to fix my labelling :) And then update (correct both problems) and share the bread-board bit on osh-park.

 

[email protected]

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Question: did you externally power things, or take the power off of the console?

 

 

Powered directly off the side port. Draws around 8mA when running a simple XB program - that will vary a bit depending on how bright your LED is (mine is fairly dim). Well within the 50mA max guideline in the console spec.

 

Nice looking PCBs!

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Stuart,

 

I'm not surprised that you got it to work... for so many reasons, but also cause you were right, the stuff is already buffered on the side-port.

 

Question: did you externally power things, or take the power off of the console?

 

Tomorrow I'll share the schematic I was trying without the buffers. In the meantime I had a couple boards printed to test, and those just arrived today.

Mem boards that are wired for the buffers, although in theory I could jumper them instead of installing the chips to test skipping the buffers..

 

And something to help keep my sanity on the bread-board.

 

attachicon.gifIMG_20160727_182653.jpg

 

attachicon.gifIMG_20160727_194418.jpg

 

attachicon.gifIMG_20160727_194442.jpg

 

I have the labelling wrong, as I didn't consider the pre-fab extension cable.. I also have the pin spacing on the edge card wrong, but am able to 'compress' the pins on the connectors I have and make it work. :)

I'll use a sticker to fix my labelling :) And then update (correct both problems) and share the bread-board bit on osh-park.

 

[email protected]

Are these available yet on OshPark, I can't seem to find them?

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What's the latest on this? Me wanty. Me wanty very much.

It is still in development. And to be open, I've got too much travel this month. Hopefully I can prepare some options while away to test once the travel subsides.

 

[email protected]

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I appreciate the enthusiasm, but the product doesn't exist yet. So I am not taking names or making any lists.

 

The first breadboard prototype worked.

 

Once i get back to the USA and recover, I hope to have time to build the proof of concept pcboard that is waiting on my desk. But as i have discussed in this thread there is another prototype breadboard design i want to get working or understand why it won't work before i do another proof of concept pcboard.

 

Then if that works out, I'll price and buy a reasonable quantity of parts. And start building them for sale.

 

If i am lucky, i have an ah-ha moment, before my next trip, and can get some steps in motion. But I would guess that we are looking at October. That is just a guess.

 

[email protected]

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