adding an FM soundchip to the ST?

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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

For anyone that's interested, I'm pretty much finished with the design of the PCB. If anyone on here is experienced with this kind of thing I'd be very happy to hear any suggestions or criticisms.

The bus control pins were the biggest challenge as upon consulting The Bible (ST Internals) it appeared that the ST keeps one of the control pins on permanently and only adjusts 2 of them, so I had to use the 2 logic chips and some diodes to adapt that to the signals the YM2203 needed.
Bus Translation.jpg
The 2 pin header blocks on the left hand edge are the outputs for the 2 parts of the sound chip, the idea being you could keep them separate for stereo sound or combine them if wanted. I plan to add a switch for this later.
PCB.jpg
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

I should note that credit for the amplifier circuitry goes to Zenmai from his YM2203 Jukebox project:
https://github.com/zenmai/YM2203_JukeBox

Also, since posting I realised I'd forgotten the 2 pulldown resistors I presume are needed for A0 and WR on the YM2203. RD is just permanently connected to the ST's YM2149 BDIR pin as it's the only one that actually matches up to something.
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Re: adding an FM soundchip to the ST?

Post by Cyprian »

nice project. would be possible to add another one to have a stereo output?
Is there any tracker for that chip or we can use e.g. maxYMiser?
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

Cyprian wrote: Tue Mar 30, 2021 8:36 am nice project.
Thanks :)
Cyprian wrote: Tue Mar 30, 2021 8:36 am would be possible to add another one to have a stereo output?
As far as I can tell the ST does not make use of the Chip Select signal which would be needed, so not easy to do without some fancy jiggery pokery :P
Cyprian wrote: Tue Mar 30, 2021 8:36 am Is there any tracker for that chip or we can use e.g. maxYMiser?
It would be relatively easy for a chip tracker to support playing notes on the extra channels but making a whole FM sound intrument editor would be a much bigger task :P I'm actually working on a music editor at the moment, which is what reminded me of the idea of putting an FM chip in an ST and of this post :)
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

I'd appreciate it if anyone could check that my logic in this spreadsheet table is sound. Between the 2 YM datasheets and ST Internals, I'm fairly happy everything else is good:
Bus Translation.gif
This is the current PCB, with some changes following some feedback and some layout simplifications. I'd be happy to send the PCB design file to anyone who wants to see what's going on more closely:
PCB.gif
I've ordered some YM2203s, Y3014 DACs, DIP-40 sockets and pin strips from AliExpress and I'll get the other parts from closer to home once I'm confident enough to get a handful of PCBs ordered.
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

So I now have a handful of these, all the way from China :)
YM2203C.jpg
I'm really hoping someone can look this over and see if I'm going about this the right way:
Bus Translation.gif
This is the how the ST talks to the YM2149:
Bus2149.jpg
and this is what the YM2203 expects:
Bus2203.jpg
If it all looks good to somebody else with some knowhow then I'll order some PCBs and hopefully it'll end up looking like this:
Render.jpg
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Re: adding an FM soundchip to the ST?

Post by Cyprian »

what about the price? I would buy mounted one.
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

Cyprian wrote: Tue May 04, 2021 6:01 pm what about the price? I would buy mounted one.
The parts are pretty cheap and I'd estimate about £40 to £50 including covering my time to assemble them. The tricky part is that the current design relies on removing the original soundchip and fitting a socket in it's place. If anyone has a better idea, I'm all ears :)
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Re: adding an FM soundchip to the ST?

Post by Cyprian »

The price sounds reasonable, I would buy one.
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Re: adding an FM soundchip to the ST?

Post by shoggoth »

I actually have a project where this thing would make perfect sens, but it needs a TT or Falcon...
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Re: adding an FM soundchip to the ST?

Post by Cyprian »

it could also be mounted in the TT/Falcon I guess

what project do you mean? a new tracker? demo?
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Re: adding an FM soundchip to the ST?

Post by shoggoth »

Cyprian wrote: Wed May 12, 2021 10:23 am what project do you mean? a new tracker? demo?
It’s an emulator, so it’s not that fun :)

The Falcon doesn’t have a DIL YM chip, but maybe the TT does. I have to check it.
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Re: adding an FM soundchip to the ST?

Post by CiH »

It’s an emulator, so it’s not that fun :)
I'm guessing MSX :wink:
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Re: adding an FM soundchip to the ST?

Post by unseenmenace »

shoggoth wrote: Wed May 12, 2021 3:33 pm The Falcon doesn’t have a DIL YM chip, but maybe the TT does. I have to check it.
It looks like TT's do in fact have a standard 40-pin DIL YM2149F, the same as STs! So that's another of my machines I'll be able to fit an FM chip to all being well :)

I found a few good motherboard pics here: http://www.atariancomputing.com/blog/at ... isionguide
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Re: adding an FM soundchip to the ST?

Post by DarkLord »

Cyprian wrote: Wed May 12, 2021 9:37 am The price sounds reasonable, I would buy one.
Same here... I'm really curious to see where the gifted individuals of
the Atari community would run with this. :)
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