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AY-3-8912 for the Coleco ADAM..?


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#1 CharlesMouse OFFLINE  

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Posted Mon Mar 18, 2019 5:52 AM

Hmm, I seem to be posting a lot for a confirmed lurker... I promise I'll stop soon.

 

I mentioned on the other thread I started that I was looking in to doing an AY sound chip upgrade for the ADAM. 

 

Why?

Well, there's some marvellous SGM games to be played but I don't have a SGM. Also, as I understand it, the ADAM will run a good deal of the SGM catalogue... quietly! (I added an extra 64k to mine a while ago)

 

As my main interest in old computers is tinkering with them I thought I'd take a crack at a SGM-compatible sound board to stick in my ADAM. I guess it would work in a Colecovision too, but without the extra RAM I don't know how useful it would be...

 

The plan:

-Come up with an AY-based design that won't be too hard to make

-Do it on the cheap, so try to stay away from expensive or hard to find components

-I really don't like having bare PCBs dangling out of my machines

 

With these thoughts in mind I decided to leave the expansion port alone and see if I could make a board that would fit in place of the Z80 as (nearly) all the required lines should be there and DIL-40 sockets aren't exactly rare.

The only required line that I'm aware is missing at the Z80 is the Audio-in to be found on Pin 31 of the expansion connector, so that will have to be a flying lead - either to be soldered somewhere suitable or as a separate line-out.

(As an aside when I did a Mockingboard clone for my Apple IIs I made sure to keep the dual AYs outputs separate for stereo but as the ADAM has only one audio-in that I know of this early prototype is mono)

 

I've attached screen-shots of my first attempt at a schematic and PCB layout. I should point out I'm aware space around the Z80 is a bit tight and so far I've only eye-balled it for space...

...um, I'm also very new to the ADAM so the schematic may have some serious errors. I'd welcome advice and suggestions if anyone has them to share.

Attached Thumbnails

  • ADAM AY-3-8912_Top.png
  • ADAM AY-3-8912_Bottom.png
  • ADAM AY-3-8912_Schematic.png


#2 chart45 OFFLINE  

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Posted Mon Mar 18, 2019 8:07 AM

it will be a painfull job to install this board since you have to unweld the z80 to install a socket... if its a personal project good

#3 Geoff Oltmans OFFLINE  

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Posted Tue Mar 19, 2019 9:03 AM

If you wanted to do this internally, depending on what expansion cards you have you may be able to do it through one of the internal slots.



#4 CharlesMouse OFFLINE  

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Posted Tue Mar 19, 2019 12:45 PM

Thanks for the feedback. :-)

 

Yep, using an expansion slot would be an easier upgrade and if there's a general wish among others for me to go that route I certainly can... I do this stuff largely for my own amusement but if my 'designs' prove useful to others I'm always pleased and so am happy to take suggestions.

 

FWIW: My current reasoning runs as follows

-Fun hardware project, so it doesn't bother me if I have to desolder and socket the Z80

-I like to at least try to keep things neat and relatively stock-looking, hence using the Z80's lines

-I try to stick with cheap and easy to source parts, mostly because I am cheap and lazy

-With the plans I currently have I'm going to need all the available expansion ports

 

-Oh, Having actually measured I'll likely need to re-do the above layout as it will interfere with a bunch of passives SW of the Z80. Either that or it's board re-work time as well as socketing the CPU. Not a biggie, but the above layout came together so well it's a shame to abandon it.

 

Um, while we're on the subject of proper expansion slots does anyone have the pin-outs for J5 and J6..? As far as I can tell the TRM lists the signals but not the pins and I'm not sure I wholly trust/understand the schematic I have.

 

 

PS

I guess I'll never get my hands on an F18a so:

a) Does anyone have access to the schematics / gerbers / system files required to DIY one?

failing that

b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are? 

-Software and pin-compatible - awesome

-Software compatible - ok, that's an adaptor board and maybe some wiring

​-Neither - give up, I'm a rotten coder

 

Thanks again.


Edited by CharlesMouse, Tue Mar 19, 2019 12:48 PM.


#5 Tursi OFFLINE  

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Posted Tue Mar 19, 2019 5:17 PM

b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are? 

-Software and pin-compatible - awesome

-Software compatible - ok, that's an adaptor board and maybe some wiring

​-Neither - give up, I'm a rotten coder

 

Thanks again.

 

They are "reasonably" compatible from a software interface only... pinouts are different and normally they host more than 16k of RAM (but it looks like 16k is legal). Software that uses undefined register bits tends to have problems (and in the TI world, we found there was more than we expected). Most stuff will likely work out of the box.



#6 NIAD OFFLINE  

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Posted Tue Mar 19, 2019 8:39 PM

Aside from the fact that you would prefer an internal option for the AY-3-8912 sound chip, have you seen the extrernal version that chart45 has already designed that is detailed in this thread:

 

http://atariage.com/...ip#entry4159023

 

Not all ADAMs are created equal and can play SGM games sans AY sound output without the Opcode SGM connected. I have one that will and one that won't.



#7 mr_me OFFLINE  

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Posted Wed Mar 20, 2019 3:19 AM

...
 
PS
I guess I'll never get my hands on an F18a so:
a) Does anyone have access to the schematics / gerbers / system files required to DIY one?
failing that
b) I know d*mn-all about the Ti9918 and as I'm asking questions, and lazy, does anyone know how 'compatible' the later (Yamaha) versions are?
-Software and pin-compatible - awesome
-Software compatible - ok, that's an adaptor board and maybe some wiring
-Neither - give up, I'm a rotten coder

...

I thought an f18a mk2 update is planned. Did you ask? http://atariage.com/...80138-f18a-mk2/

You're probably busy, not lazy.

Edited by mr_me, Wed Mar 20, 2019 3:24 AM.


#8 Geoff Oltmans OFFLINE  

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Posted Thu Mar 21, 2019 8:59 AM

A while back I was starting to do schematic capture for a Yamaha 9938/9958 upgrade board. I'd like to do one using SRAM instead of DRAM  (using a CPLD to demux the DRAM addressing) to reduce part count and use more modern RAMs.

 

I used to have a TIM board for my ADAM that I scavenged from a TI 99/4A, it worked, mostly. The first hurdle is that you must program the palette registers used by the older video modes as by default all the colors are set to black, so nothing would display. There were some other gotchas, but I like the idea of using a 9938 or 9958 on the ADAM, and I think a DIY project could be pretty inexpensive.



#9 CharlesMouse OFFLINE  

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Posted Sat Mar 23, 2019 8:35 AM

 

They are "reasonably" compatible from a software interface only... pinouts are different and normally they host more than 16k of RAM (but it looks like 16k is legal). Software that uses undefined register bits tends to have problems (and in the TI world, we found there was more than we expected). Most stuff will likely work out of the box.

 

Thanks for the reply, and info. :-)

I guess that's at least hopeful, I shall have to pull my finger out and take a proper look myself & see if I can do it. 

 

Of course I'd much prefer an F18a at some point. I got the impression they were pretty-much permanently out of production, but I'd be very happy indeed to be proven wrong. More Googleing required...

 

Back on topic:

After further measurement my initial take on a Z80-socket AY board won't fit the Delta board of the ADAM without messing about with some caps. I've yet to check clearances in the Colecovision itself as I've just remembered the Expansion Module 3. So I've done an update for that, that will fit and happily the West pin of C88 looks to be a good spot to hook-up the AY's output.

Oh, and I quite understand that if there is anyone interested in following along they may not be that charmed about desoldering the Z80 from their precious, and likely delicate, ADAM so I've come up with two further options:

1) I've done a spin on the board that should work in the side-expansion socket

2) It would be easier (but permanent) to first solder my Z80 board's pin-headers to the shoulders of the Z80 and then solder the otherwise completed board to them. I really, really wouldn't do that until I've at least proven this design actually works!!!

 

Please find attached piccies of my schematics and boards. I'll zip-up the Eagle files and post Gerbers if anyone's interested. I don't know when I'll get round to having the Z80 board made, but will at the least let everyone know how it goes...

 

PS

Yes, the boards have good VCC and GND fills (for two layer boards) but not shown in the images as as not to obscure the traces.

Attached Thumbnails

  • ColecoAYZ80_SCH.png
  • ColecoAYZ80_BRD.png
  • ColecoAY2_SCH.png
  • ColecoAY2_BRD.png

Edited by CharlesMouse, Sat Mar 23, 2019 8:41 AM.


#10 Tursi OFFLINE  

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Posted Sat Mar 23, 2019 5:05 PM

Of course I'd much prefer an F18a at some point. I got the impression they were pretty-much permanently out of production, but I'd be very happy indeed to be proven wrong. More Googleing required...

 

Don't buy into the rumor mill. I work with the guy who makes them and we talk almost daily about it. V2 is coming. Hobby projects are just subject to real life interference. ;)



#11 CharlesMouse OFFLINE  

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Posted Wed Mar 27, 2019 8:18 AM

@Tursi:

Thank you very much for the most welcome information. If it's not too cheeky for me to ask would you mind letting the chap who makes these I'd really like one, along with an ADAM adaptor board if the new version requires that, when v2 is out?

 

Many thanks and do please pass on my sincere thanks for his efforts on this excellent project.

 

News:

I'm about to send off the Gerbers to Seeed Studio (my favourite DIY PCB fab house) to do a board or two based on my attempt. I'm having the Z80 socket version made as that's the one I'm interested in but I've also produced the necessary files for any who want to make their own but would rather go the side-expansion route...

...please be advised that if anyone is interested in making their own I would wait until I've reported back to (hopefully) say the design actually works. (Seed Studio usually turns jobs around in about 2 weeks) Also while the side-expansion version is all-but identical to the Z80 socket board I've no intention of making one of those myself so any who do go with that one will be using an untested design!

 

Gerbers for both are attached.

Attached Files



#12 Tursi OFFLINE  

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Posted Wed Mar 27, 2019 12:23 PM

@Tursi:
Thank you very much for the most welcome information. If it's not too cheeky for me to ask would you mind letting the chap who makes these I'd really like one, along with an ADAM adaptor board if the new version requires that, when v2 is out?


No worries, but he uses his waiting list for that, so just make sure you're signed up at his page ;)

#13 CharlesMouse OFFLINE  

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Posted Wed Mar 27, 2019 2:34 PM

No worries, but he uses his waiting list for that, so just make sure you're signed up at his page icon_wink.gif

Thank you again - I have now left a message.



#14 soviet OFFLINE  

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Posted Thu Mar 28, 2019 12:20 PM

Cool i could love to see this working :D






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