Putting a YM2203 FM soundchip in place of the YM2149

[qq1975b]

Here’s an example of the 2203 plying all its six voices
https://youtu.be/qSWCihT_2Ho

It sounds very good.

[viking272]

That video replay was of amazing quality. How's the progress for this project?

[Steve]

I hope he comes back for this, it looked so promising.. but his profile says:

Last active:
Thu Jan 13, 2022 6:29 pm

:(

[unseenmenace]

I'm not dead, just hadn't logged into this forum in a while, sorry everybody. The project has been on hold as I wanted someone with more experience than myself to go over my soundchip control line conversion logic and I'm hoping a certain someone will be willing to provide some feedback following a direct message I got on here a while back but had not seen. This is the current design, I've made a few changes following feedback I've gotten and things I've learned since starting this (such as a dedicated power input and a semi isolated ground-plane for the audio circuitry) and as soon as someone backs up my control line logic as making sense I will get a prototype PCB or 2 ordered, as I have a bit more disposable income than I did when I first started looking into this as I got a much better paying job last year :) :

Render-2.jpg

PCB-2.jpg

[Cyprian]

keep finger crossed

[nokturnal]

@unseenmenace Cool project.. I've got vgm player already for opl2/3. I could help with it. I think it would be just a question of writing proper driver for it and handling ym2203 commands. Someone wrote that this chip could end up in Sts, but for some reasons didn't. Is this true? It could bring a massive difference back in 85..And I wonder what is the source of this rumour?
How programmer interface of it looks like? How this hardware can be detected from os?
How audio of this chip is integrated into st hardware? Does it need extra output connectors or sound is mixed somehow into st audio output?

[unseenmenace]

@unseenmenace Cool project.. I've got vgm player already for opl2/3. I could help with it. I think it would be just a question of writing proper driver for it and handling ym2203 commands.

Thanks, I'm always happy for any help anyone can offer! I'm actually working on a stave based music program similar to Quartet that I plan to add support for the YM2203 to.

Someone wrote that this chip could end up in Sts, but for some reasons didn't. Is this true? It could bring a massive difference back in 85..And I wonder what is the source of this rumour?

I have read that they originally wanted a Yamaha FM synth sounchip for the ST (though I think it was a more advanced one than the YM2203) but they changed plans to keep costs down.

How programmer interface of it looks like? How this hardware can be detected from os?

The reason I picked the YM2203 is because it contains everything the YM2149 does (and has a very similar pinout) but just has a few extra registers to control the extra FM sound channels. You set parameters exactly the same way as the 3 square-wave PSG channels present in both the YM2149 & YM2203.

How audio of this chip is integrated into st hardware? Does it need extra output connectors or sound is mixed somehow into st audio output?

You could have the 3 square-wave channels just go back into the ST's motherboard and be fed out of the monitor socket but the FM sound has it's own separate digital output requiring a Yamaha DAC chip and amplifier which would complicate merging the outputs together, hence the design of my PCB gives you the choice of 3 different ways to handle all the sound outputs:

1. All 3 PSG channels and the 3 FM channels merged into a single mono output
2. The 3 PSG channels combined into the left output and the FM channels into the right output
3. PSG 1 to left output, PSG 2 lowered and sent to left and right, PSG 3 to right output and FM output to both left and right

Ideally you'd mount some phono sockets or a stereo jack socket to the rear of the ST for this and connect to the chosen output from the PCB.

[nokturnal]

@unseenmenace Regarding vgm player pm me, so we will arrange something.

[chronicthehedgehog]

Cool project. I've been playing around with MaxYMiser a lot recently so it got my interest.

I especially like projects that won't destroy my bank balance :)

Just a thought.. since it would require socketing the YM anyway. The means to retro fit a floppy drive A/B switch would be nice. Tented vias or something.

[nokturnal]

@unseenmenace I've wrote preliminary support for YM2203, so I can parse ym2203 VGM tunes right now, so the only thing needed is just fill in like three driver functions and done (init/deinit/write). So give a shout, when you will have something working..