Progress of my MT-32pi project (with smaller case)

[Mu0n]

Goals of the project:

-Have a small raspberry pi3 deal with MIDI data and playback sound for both Roland MT-32 and Roland Sound Canvas-55 (bonus: other sounds with general midi sound fonts)
-Not set it as a pi hat
-Put it in a small and cute very transportable custom case

Use cases:

Many people resort to this for their Mister solutions, since you can't run a 486 or mac core at the same time as a MIDI synth, at least not yet. This is mostly for an era between 1987-1991 (Roland MT-32) right before general midi solidified as a standard and then the later GM era (1992-1996) before everything became mp3s and synthetizing music was no longer necessary with ample compression + storage + quality.

Anything that sends MIDI data through a std MIDI cable is fair game, which could include PCs, Macs, Atari STs, etc. My favorite use case is the DOS gaming epoch covering both types of synth modules.

Links:

Project page
Vogons thread on custom cases

Minimal resources needed:

-Supports Raspberry Pi Zero 2 W, Raspberry Pi 3 Model A+, B, and B+, Raspberry Pi 4 Model B, and CM4 series. (I'm using a 3a, less USB ports means its volume is smaller than a 3b)
-Very normal microSD card, probably 1Gb and up is fine, unless you want more sound fonts
-Something that outputs MIDI data to a midi cable
-MIDI female connector
-H11L1M optoisolator
-220 Ohm and 1000 Ohm resistors
-100 nF cap
-A diode
-A few wires to connect to the pi3 GPIO pins

Extra functionality

-PCM5102 i2S dac board
-16x2 LCD screen (lots of screens are supported, check the docs)
-KY-040 rotary encoder for the volume knob
-2 micro switches

MIDI connection schematic

 

[Mu0n]

Here are some progress shots on the ol' breadboard first:

Working condition with just my pi3b (while I wait for the 3a to arrive) in headless mode (this project's software has no video output anyway), no controls or LCD screen

Addition of the LCD screen:

Addition of rotary encoder + 2 control button switches:

Next step is to take this mess of wires and transport and solder it all on one of these protoboards (I got an assorted kit here):

 

[Mu0n]

Case inspiration:

I plan to redo pretty much this design, roughly. I found this in a thread on vogons forum.

After repeated inquiries by a few other people and me, he still hasn't posted his fusion360 files so that we can adapt and 3d print his design.

It's about half size compared to the real thing:

I plan to design a black solder masked PCB for the front piece, as soon I as get more comfortable in EasyEDA. As for the protective layer above the screen, I have a local friend that can cut and design acrylic as well has several 3d printing machines, so that shouldn't be an issue at all.

Gonna prototype the case dimensions first in foamcore for a quick and dirty hands on IRL 3d model first.

 

[Mu0n]

I've started exploring a mock case in foamcore to get a general sense of how I want to assemble it. It seems like the MT-32 panel is at a 60 degrees angle.

I won't be using the pi3 USB ports at all. The ports that should go out are: area large enough for the microSD to be inserted in/out, MIDI in, micro USB power, audio mini-jack, 2 microswitches with 3d printed rectangular button covers, the rotatry encoder poking out 2/3rds of the way.

The toothpicks are there to test out different angles for the front panel.

 

[Mu0n]

I've started working on the faceplate recreation/adaptation of my front plate, shown here with a side by side comparison with the real thing:

I found other people working on a font, this one is called PBIO:

but the M and 3 of MT-32 seem wrong, and the multi & sound sentences look too fat (bold).

so I found a TR-909 font somewhere, which is much better:

looks nice huh? However, I pixel matched the Roland (had to be squished vertically a slightly stretched horizontally) and then I noticed that the T of MULTI has to overhang above the L, so here we are at the end:

it's not 100%, I could do a pixel match for these, but NO ONE WILL EVER NOTICE without being told, so I'll call it a day.