MiSTer FPGA Forum

I am currently designing a custom case for MiSTer. One of the main sticking points for me is whether or not to integrate the MT32-Pi. After some digging, I was quickly confused, so thought I'd ask here.

I have three main questions about the MT-32 Pi:

1) How necessary are a screen and physical buttons? Do these allow extra features or make using much easier? Could I just bury the unit inside a closed case (with airflow?) if I don't use them? The case is not tiny (190x200x100mm tower format) but I don't want to waste space and cram the thing full if I don't have to.

2) If a screen does add a lot, I would really love a LCD screen, green or yellow, to hearken back to the original MT-32. My problem is, to fit my current design, a screen would need to be 25x45mm in height and width max to fit. I found the page at this link: https://github.com/dwhinham/mt32-pi/wik ... D-displays with some compatible options, but the LCD screens are all 70-80mm wide. I don't know if anyone has happened to find anything that seems to fit those dimensions? Worst case, I could use a small OLED screen. These are not my favorite but they will fit in my available space and get the job done.

3) Where to buy a pre-made MT-32 Pi? I see them on UltimateMiSTer but I am in the US and can't seem to pull up any other options with a simple search. Also, if I do purchase a pre-made unit, could I swap the screens if I found a compatible unit that fit the dimensions and look I want?

Bonus!) I have also just heard about the Pi-Midi, which is similar to the MT-32 Pi but seems to be more general-use. Should this be considered over the MT-32 Pi?

Deatils of the mt32-pi for MiSTer are on the wiki here:

https://github.com/dwhinham/mt32-pi/wiki/MiSTer-FPGA

For a list of current mt32-pi sellers for MiSTer, they are on the mt32-pi wiki here:

https://github.com/dwhinham/mt32-pi/wik ... m-hardware

bozocyborg wrote: ↑Mon Dec 12, 2022 8:42 pm

1) How necessary are a screen and physical buttons? Do these allow extra features or make using much easier? Could I just bury the unit inside a closed case (with airflow?) if I don't use them? The case is not tiny (190x200x100mm tower format) but I don't want to waste space and cram the thing full if I don't have to.

2) If a screen does add a lot, I would really love a LCD screen, green or yellow, to hearken back to the original MT-32. My problem is, to fit my current design, a screen would need to be 25x45mm in height and width max to fit. I found the page at this link: https://github.com/dwhinham/mt32-pi/wik ... D-displays with some compatible options, but the LCD screens are all 70-80mm wide. I don't know if anyone has happened to find anything that seems to fit those dimensions? Worst case, I could use a small OLED screen. These are not my favorite but they will fit in my available space and get the job done.

3) Where to buy a pre-made MT-32 Pi? I see them on UltimateMiSTer but I am in the US and can't seem to pull up any other options with a simple search. Also, if I do purchase a pre-made unit, could I swap the screens if I found a compatible unit that fit the dimensions and look I want?

Bonus!) I have also just heard about the Pi-Midi, which is similar to the MT-32 Pi but seems to be more general-use. Should this be considered over the MT-32 Pi?

1. You don't need the screen or buttons for this application. It'd probably be nice to have access to the SD card slot though in case you need to do any updates.

2. Best I can say is hunt through https://www.aliexpress.com/wholesale?Se ... 44780+20x4 and https://www.aliexpress.com/wholesale?Se ... 44780+20x2

3. Pre-made MT32-Pi hat, or one bundled with a Pi? Raspberry Pis are very hard to get right now. You could put any I2C screen out there (or even other than I2C) on it, might involve some soldering, and you'd need a driver for it.

What's necessary comes down to your own personal preferences and what you're going to use it for. You said this is for a custom MiSTer case so it doesn't sound like you're going to use it as a synthesizer replacement (connecting to real PC hardware or MIDI keyboards). Anything that has additional functions for using as a synthesizer will go to waste. The mt32-pi project added MiSTer functionality so it can sync up with a menu interface rather than requiring any buttons or screen. Plus, it sends the sound right through MiSTer's sound output so no having to get a mixer to combine the audio out to the speakers like a real synthesizer would need to do. That's why there's the mt32-pi Lite that is just a simple, faceless build based on the Pi Zero 2. The controls potentially useful for MiSTer can all be controlled through the core menus. And in the case of the ao486 core, there's also the option for an on screen LCD to see the quick start up messages and such. If all you're going to use an mt32-pi for is the MUNT MT-32 emulation function then you honestly don't need anything more. And since the Pi Zero 2s seem to be a bit easier to find on their own or as completed builds, that might be preferred in this current age of Pi manufacturing drought and scalpers.

If you're interested in using the FluidSynth General MIDI functionality, this is where it gets more complicated and you might be interested in more build features. The ao486 core is able to take advantage of General MIDI because some later DOS games and Windows games had support for it. If you're using just the mt32-pi menu in the core, you're limited to 8 total SoundFonts. The menu only goes from 0 to 7; doesn't matter if you have more on there or not. Depending on your use case, that could be a lot or not enough. Considering just how varied in quality many SoundFonts are, I personally find 8 to be plenty enough for a few era appropriate SoundFonts (like for the Sound Canvas SC-55 or Gravis Ultrasound), a couple of high quality beyond the tech age SoundFonts (such as Arachno SoundFont or Timbres of Heaven), and a few jokey ones based on game consoles (Genesis, SNES, whatever). More than 8 and you need to have physical buttons in order to cycle though SoundFonts manually. A screen might be useful there to know you're definitely switched to FluidSynth mode and also which SoundFont you're attempting to load (rather than having to wait out the load process and guess which one is selected). But this is definitely up to personal use case. There's a lot of SoundFonts available on the internet but so many of them are just not worth it for long term enjoyment or are missing instruments. I personally find it better to audition them on my computer first and then put my favorites into the 8 slots for my MiSTer. As funny as it is to play Doom with an NES SoundFont, the joke is quickly lost as it becomes clear that it doesn't have enough unique sounds to do it right.

And lastly, keep in mind the size of the RAM of the Pi. The amount of RAM and the size of the SoundFont you can load are directly correlated. You can't load a SoundFont bigger than the amount of RAM (with also a small amount taken out for the mt32-pi system). Era appropriate SoundFonts will be no problem but some SoundFonts can definitely surpass the 512MB of the Pi Zero 2 or often used smaller Pi 3 Model A+. I personally can't get Timbres of Heaven V4 to load on my Pi Zero 2 based build and there are some others that definitely wouldn't fit which is why I also have my Pi 3 Model B fitted with the hat if I really want to load them on my MiSTer. But honestly, I go back to ones that are small enough to work on the Pi Zero 2. I prefer the sound of the Arachno SoundFont over Timbres of Heaven and it's less than half the size of it as well. A large SoundFont may just be bloated with sounds and not an indication of quality. In the case of Timbres of Heaven, no 486 PC game is taking advantage of the Yamaha XG MIDI instruments that's making up some of its size and the rest of it is unbalanced to my taste. But you really have to test and decide for yourself what sounds better and your preferences in SoundFonts will matter in choosing a Pi (and subsequently the kind of circuit board build needed).

I bought my full mt32-pi Lite build through UltimateMiSTer and the mt32-pi hat I use on my Pi 3 from MiSTerAddOns (which also has SNAC pass through with a toggle switch). It's easier to find builds without a Pi included than with one nowadays. That's just how bad availability of Pi devices are. I think the limited connections of the Pi Zero 2 are what help the full mt32-pi Lite builds to pop up more often since people prefer the full boards over forced dongles. If the mt32-pi is specifically for MiSTer and never going to be used as a full synthesizer replacement, I'd recommend sticking to MiSTer focused sellers that will offer builds or Pi hats that are meant to be used with MiSTer. You'll get the best compatibility and ease of setup that way. And to answer the bonus about PiMIDI, that looks to be just an interface board. That's like if you already had a Roland MT-32 synthesizer and you want to connect it up to a computer. PiMIDI is not a synthesizer, just a connector.

Xbytez wrote: ↑Mon Dec 12, 2022 10:37 pm

Deatils of the mt32-pi for MiSTer are on the wiki here:

https://github.com/dwhinham/mt32-pi/wiki/MiSTer-FPGA

For a list of current mt32-pi sellers for MiSTer, they are on the mt32-pi wiki here:

https://github.com/dwhinham/mt32-pi/wik ... m-hardware

Thank you, I totally looked over the seller links!

thisisamigaspeaking wrote: ↑Tue Dec 13, 2022 12:53 am

1. You don't need the screen or buttons for this application. It'd probably be nice to have access to the SD card slot though in case you need to do any updates.

2. Best I can say is hunt through https://www.aliexpress.com/wholesale?Se ... 44780+20x4 and https://www.aliexpress.com/wholesale?Se ... 44780+20x2

3. Pre-made MT32-Pi hat, or one bundled with a Pi? Raspberry Pis are very hard to get right now. You could put any I2C screen out there (or even other than I2C) on it, might involve some soldering, and you'd need a driver for it.

I will sift through those screen options, I like the look of some already!

Right now I have a Pi 3B that I could use. I'd prefer a Zero model but hate to pay current inflated prices. I will stay on the lookout though since that's a lot of space saved.

Do you know if it is an issue to have the screen mounted at the front of the case and the Pi further back? Is it an issue to have a few inches of cabling between them?

DevilHunterWolf wrote: ↑Tue Dec 13, 2022 8:51 am

What's necessary comes down to your own personal preferences and what you're going to use it for. You said this is for a custom MiSTer case so it doesn't sound like you're going to use it as a synthesizer replacement (connecting to real PC hardware or MIDI keyboards). Anything that has additional functions for using as a synthesizer will go to waste. The mt32-pi project added MiSTer functionality so it can sync up with a menu interface rather than requiring any buttons or screen. Plus, it sends the sound right through MiSTer's sound output so no having to get a mixer to combine the audio out to the speakers like a real synthesizer would need to do. That's why there's the mt32-pi Lite that is just a simple, faceless build based on the Pi Zero 2. The controls potentially useful for MiSTer can all be controlled through the core menus. And in the case of the ao486 core, there's also the option for an on screen LCD to see the quick start up messages and such. If all you're going to use an mt32-pi for is the MUNT MT-32 emulation function then you honestly don't need anything more. And since the Pi Zero 2s seem to be a bit easier to find on their own or as completed builds, that might be preferred in this current age of Pi manufacturing drought and scalpers.

If you're interested in using the FluidSynth General MIDI functionality, this is where it gets more complicated and you might be interested in more build features. The ao486 core is able to take advantage of General MIDI because some later DOS games and Windows games had support for it. If you're using just the mt32-pi menu in the core, you're limited to 8 total SoundFonts. The menu only goes from 0 to 7; doesn't matter if you have more on there or not. Depending on your use case, that could be a lot or not enough. Considering just how varied in quality many SoundFonts are, I personally find 8 to be plenty enough for a few era appropriate SoundFonts (like for the Sound Canvas SC-55 or Gravis Ultrasound), a couple of high quality beyond the tech age SoundFonts (such as Arachno SoundFont or Timbres of Heaven), and a few jokey ones based on game consoles (Genesis, SNES, whatever). More than 8 and you need to have physical buttons in order to cycle though SoundFonts manually. A screen might be useful there to know you're definitely switched to FluidSynth mode and also which SoundFont you're attempting to load (rather than having to wait out the load process and guess which one is selected). But this is definitely up to personal use case. There's a lot of SoundFonts available on the internet but so many of them are just not worth it for long term enjoyment or are missing instruments. I personally find it better to audition them on my computer first and then put my favorites into the 8 slots for my MiSTer. As funny as it is to play Doom with an NES SoundFont, the joke is quickly lost as it becomes clear that it doesn't have enough unique sounds to do it right.

And lastly, keep in mind the size of the RAM of the Pi. The amount of RAM and the size of the SoundFont you can load are directly correlated. You can't load a SoundFont bigger than the amount of RAM (with also a small amount taken out for the mt32-pi system). Era appropriate SoundFonts will be no problem but some SoundFonts can definitely surpass the 512MB of the Pi Zero 2 or often used smaller Pi 3 Model A+. I personally can't get Timbres of Heaven V4 to load on my Pi Zero 2 based build and there are some others that definitely wouldn't fit which is why I also have my Pi 3 Model B fitted with the hat if I really want to load them on my MiSTer. But honestly, I go back to ones that are small enough to work on the Pi Zero 2. I prefer the sound of the Arachno SoundFont over Timbres of Heaven and it's less than half the size of it as well. A large SoundFont may just be bloated with sounds and not an indication of quality. In the case of Timbres of Heaven, no 486 PC game is taking advantage of the Yamaha XG MIDI instruments that's making up some of its size and the rest of it is unbalanced to my taste. But you really have to test and decide for yourself what sounds better and your preferences in SoundFonts will matter in choosing a Pi (and subsequently the kind of circuit board build needed).

I bought my full mt32-pi Lite build through UltimateMiSTer and the mt32-pi hat I use on my Pi 3 from MiSTerAddOns (which also has SNAC pass through with a toggle switch). It's easier to find builds without a Pi included than with one nowadays. That's just how bad availability of Pi devices are. I think the limited connections of the Pi Zero 2 are what help the full mt32-pi Lite builds to pop up more often since people prefer the full boards over forced dongles. If the mt32-pi is specifically for MiSTer and never going to be used as a full synthesizer replacement, I'd recommend sticking to MiSTer focused sellers that will offer builds or Pi hats that are meant to be used with MiSTer. You'll get the best compatibility and ease of setup that way. And to answer the bonus about PiMIDI, that looks to be just an interface board. That's like if you already had a Roland MT-32 synthesizer and you want to connect it up to a computer. PiMIDI is not a synthesizer, just a connector.

Thank you for the Pi-Midi info!

All I really want is to be able to hear high-quality MIDI sound in DOS, x68K, PC-98 (once that core matures), and other games. It sounds like buttons and screen add a big ease-of-use upgrade for switching to other soundfonts like the Soundcanvas. I do not think I will bother with modern soundfonts, or at least none that are too different from the older ones.

You probably don't really need the screen. It doesn't detract, but it's also not that important. I have one, but almost never look at it. Even if it was convenient and easy to see, I don't think I would care.

The MT32-Pi is fully controllable from the onscreen menu system, so you don't actually need the buttons for anything when you're using it with the Mister. I don't even remember which button does what.

Note that the biggest user of the MT32 on the Mister is the AO486 core, which is kinda bad. It has fairly serious bugs, and there are quite a lot of games that don't run well or at all. You can work around some of the problems, sometimes, by substituting the DOS32A DOS extender for the DOS4GW runtime, but many games remain unfixed.

The Amiga core can use it, but there's only a few Sierra games that have MIDI, since the Amiga had pretty decent onboard sound. AFAIK the Atari ST core can use it as well, and probably more games there will use it, since all real Ataris had MIDI ports onboard. And the Sharp X68000 core has quite a few games that can be toggled to MIDI mode.

Overall, it's not that critical. You can skip it completely without missing out on too much.

On my hat, you can't separate the Pi from the display. But, again, you probably don't care about the display. If you do buy one, just stick the whole thing inside the case, and make sure there's some airflow, as it can get fairly warm.

edit: Sierra games would sometimes send custom graphics to the MT32's display, usually the name of the game. That's kinda cool, and at least a little bit of a reason to have it visible.

I really like my MT32-Pi. I remember when I was a teenager, just dreaming of the Roland. Looking at the price knowing I would never own one.
It MT32-PI really works well.

Don't cores supporting MT-32pi offer an on-screen display that exactly mirrors the LED one?

I know at least some have the display, but doesn't it block part of the screen?

Where can I even buy an assembled Pi-Midi?

Malor wrote: ↑Wed Dec 14, 2022 7:10 pm

You probably don't really need the screen. It doesn't detract, but it's also not that important. I have one, but almost never look at it. Even if it was convenient and easy to see, I don't think I would care.

The MT32-Pi is fully controllable from the onscreen menu system, so you don't actually need the buttons for anything when you're using it with the Mister. I don't even remember which button does what.

Note that the biggest user of the MT32 on the Mister is the AO486 core, which is kinda bad. It has fairly serious bugs, and there are quite a lot of games that don't run well or at all. You can work around some of the problems, sometimes, by substituting the DOS32A DOS extender for the DOS4GW runtime, but many games remain unfixed.

The Amiga core can use it, but there's only a few Sierra games that have MIDI, since the Amiga had pretty decent onboard sound. AFAIK the Atari ST core can use it as well, and probably more games there will use it, since all real Ataris had MIDI ports onboard. And the Sharp X68000 core has quite a few games that can be toggled to MIDI mode.

Overall, it's not that critical. You can skip it completely without missing out on too much.

On my hat, you can't separate the Pi from the display. But, again, you probably don't care about the display. If you do buy one, just stick the whole thing inside the case, and make sure there's some airflow, as it can get fairly warm.

edit: Sierra games would sometimes send custom graphics to the MT32's display, usually the name of the game. That's kinda cool, and at least a little bit of a reason to have it visible.

Tanks for the pragmatic viewpoint. I've used the ao486 core quite a bit and I am really impressed. As you said, many games I try to launch are still not working or perfect, and I have only tried workarounds for a few, but I can see a lot of potential. That said, I haven't tried MT-32 with anything so that may break even more things.

I would really like a display, but I am torn. It seems to add a lot of complexity to a case design when accounting for the Pi and hat behind it.

The MT32 shouldn't break anything. If you're getting good value out of the AO486 now, and if those games support MIDI output, then adding the board should be purely an improvement.

Most of those tiny OLED displays are really cheap, so you can just put one on the board now. Then, later on, you can either ignore it or try to figure out how to mount it. Keep in mind that the cable from the user port on the Mister needs to be very short (six inches or less), so you can't take it very far. The timings on the MT32-Pi connection are very, very tight. A long cable will probably be too slow to work. You'll want to try to mount the user port close to the case side you want to use for the display.

bozocyborg wrote: ↑Wed Dec 14, 2022 3:02 pm

Do you know if it is an issue to have the screen mounted at the front of the case and the Pi further back? Is it an issue to have a few inches of cabling between them?

I've done a little bit of work with I2C and it is pretty robust. I am not an expert in that though. AFAIK the wires could be as long as you would need it for a case, no problem.

When I was figuring out how to get an MT32-Pi up and running, I saw a lot of complaints about problems with longer cables. I think maybe they loosened the signal timings just a bit, but AFAIK you still want a short cable if possible. That was sort of the go-to diagnostic for MT32-Pi problems, the first thing people asked, almost.... "how long is your cable?"

Malor wrote: ↑Thu Dec 15, 2022 4:19 pm

When I was figuring out how to get an MT32-Pi up and running, I saw a lot of complaints about problems with longer cables. I think maybe they loosened the signal timings just a bit, but AFAIK you still want a short cable if possible. That was sort of the go-to diagnostic for MT32-Pi problems, the first thing people asked, almost.... "how long is your cable?"

If this was a reply to me, this was in regards to separating the display from the circuit board and running the I2C over wires, not the cable from the Pi to the I/O board.

thisisamigaspeaking wrote: ↑Thu Dec 15, 2022 4:46 pm

Malor wrote: ↑Thu Dec 15, 2022 4:19 pm

When I was figuring out how to get an MT32-Pi up and running, I saw a lot of complaints about problems with longer cables. I think maybe they loosened the signal timings just a bit, but AFAIK you still want a short cable if possible. That was sort of the go-to diagnostic for MT32-Pi problems, the first thing people asked, almost.... "how long is your cable?"

If this was a reply to me, this was in regards to separating the display from the circuit board and running the I2C over wires, not the cable from the Pi to the I/O board.

Yes, I was only looking for advice on having the display mounted on the front of the case, and wires ran to the interior of the case (6-8" wires) to the Pi/hat mounted elsewhere near the MiSTer. I will be sure to keep that distance very short (probably mount the two side by side).

thisisamigaspeaking wrote: ↑Thu Dec 15, 2022 4:46 pm

Malor wrote: ↑Thu Dec 15, 2022 4:19 pm

When I was figuring out how to get an MT32-Pi up and running, I saw a lot of complaints about problems with longer cables. I think maybe they loosened the signal timings just a bit, but AFAIK you still want a short cable if possible. That was sort of the go-to diagnostic for MT32-Pi problems, the first thing people asked, almost.... "how long is your cable?"

If this was a reply to me, this was in regards to separating the display from the circuit board and running the I2C over wires, not the cable from the Pi to the I/O board.

Aha, I completely misunderstood. I thought the user port was maybe using i2c.... I almost asked about that, but didn't quite.

The short cable thing is important for the Mister->Pi user port cable, but I know absolutely nothing about detaching the display, other than thisisamigaspeaking's post, which sounds both plausible and easy. You might be able to use a 3.5" drive cover to mount it; if you mess up the hole, those things are a dime a dozen, and you could keep trying until it came out exactly right.

I think most displays would easily fit in a 3.5" cover, but verify before ordering your case.

The cable length between the mt32-pi and the MiSTer is dependent on whether or not the User IO port is also powering the Pi and hat. If the Pi is getting power separately through its own power port, then the cable can be longer because it's strictly data transfer. If the MiSTer User IO port is powering the Pi, then it has to be very short to handle both power and data transfer without problems. I originally found this info on d0pefish's Ko-Fi shop page for the official mt32-pi he made but the store page is gone since it's been out of stock for so long. But that's why his mt32-pi has the Ext Pwr port to give people the option of using either: super short cord for simple setup or separate power for easier positioning. I believe that's also why the hat on MiSTerFPGA.co.uk's site has its toggle switch to allow both options.

So if you are giving the Pi power separately, the cable can be longer to allow positioning the mt32-pi elsewhere. Just something to potentially consider.