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More MIDI Stuff & All In Ones

A project log for OPL Studio - OPL2 / OPL3 MIDI Interface

a MIDI interface for the OPL2 Audio Board and OPL3 Duo!

maarten-janssenMaarten Janssen 01/04/2023 at 15:360 Comments

Availability Of Units

The first run of OPL Studio kits has been sold. Thanks to everyone who bought a unit! More OPL Studios will be available through January as the situation around the availability of Teensys is improving and additional components for the OPL3 Duo are also on the way.

Software Update

The upcoming software update will include some great new features on the MIDI front. First of all you will have the option to export you OPL Studio compositions to a .MID file and it allows you to include your instrument patches and synth settings as SysEx data so other MIDI players can read the patch data and exactly reproduce the song as it was played on OPL Studio.

Besides saving to MIDI there will be a new media player module that allows you to play .MID files from the SD card. This can also be, of course, MID files that you exported on OPL Studio with custom instrument patches. Later the media player may support more OPL2 / OPL3 music formats for example tracked music such as .RAD (Reality Adlib Tracker). The media player is practically ready except for the SysEx support and some optimizations for seeking backward in multi-track MIDI files.

In an earlier update I already changed the calibration of the CV/T inputs by adding an auto calibrate function. The manual calibration is nice when you have a pot that you turn by hand to calibrate the range, but when you're taking an input from a fluctuating signal the manual calibration doesn't make much sense. That's where the auto calibration comes in to sample the input and make calibration much easier.

Next to this the next software update will likely change the LCD dirver code to a driver that is aimed toward using it on a Teensy instead of the generic dirver I'm currently using to improve stability of the LCD (see below). Of course there will be some bug fixes and changes behind the scenes to make the UI more flexible, for example support for different icons per file in the file chooser. 

All In One Units

The all in one units that merge the OPL3 Duo and OPL Studio are progressing well. It's a full redesign of the PCB since for the all in ones I'm moving to SMD components as much as possible to make it easier to manufacture.

This also means that the all in ones will, probably, not be available in kit form, because I want to guarantee a working unit and I rely on OPL3 chipsets from Chinese vendors. There is usually nothing wrong with the OPL3s sourced from these vendors, but as I've learned with the OPL2s it's better to be safe than sorry!

One thing I'm most unhappy about in the current unit is the stability of the LCD. Ocasionally the display goes blank, inverse or the colors are slightly off. Often this is fixed by going in and out of standby, but that's just a workaround and it prevents me from driving the LCD at a higher bus speed. One fix I'm looking into is replacing the current LCD driver code with a driver that's specific to the Teensy instead of the generic one I'm using right now. Besides that the physical connection of the LCD to the main board using pin headers is probably not optimal to drive the screen at high speeds. So I'm trying alternative ways to mount the screen.

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