Since writing my last log I've had a few very long and frustrating debug sessions. I was facing an increasing number of unexplained bugs where synthesizer functions would mysteriously stop working even though I was sure I had left the code in a working state. Only after dumping a huge amount of logs over serial, all of which looked fine, I finally found the issue after a full week of debugging. My mystery bugs were caused by intermittent connections on my breadboard! Frustrated, yet relieved I decided that it was time to start working on a more permanent home for the project.

PCB Prototypes

So I've been busy with KiCad to design the first prototype PCBs. There will be two PCBs that will be stacked on top of each other: a main board and a control board. The control board will have 8 LED push buttons and 8 potentiometers to change various parameters. This board will also connect to the LCD screen. The bottom board will be the main board that holds the Teensy, SD card reader, DIN MIDI in and thru connectors, 8 control voltage / trigger inputs for Eurorack synths, and all the (logic) components to connect everything together.

Settings

While I was stuck with my mystery bugs I did however continue working on another part of the OPL Studio software that wouldn't depend on the OPL3 Duo synthesizer. I started to work on the settings screens. Right now three settings screens are ready. 

The first is display settings where you can change the background color and pattern and screen brightness. 

The second settings screen is for the pointer. Here you can recalibrate the stylus and enable or disable the UI click sounds. 

This MIDI settings allow you to change the clock source between MIDI clock and the internal clock. You can enable or disable the metronome sound during recording and you can select the depth of pitch bends between 1 seti-tome or the default 2 semi-tones. That last setting I included because I found that there are quite a number of MIDI tunes that don't respect the GM standard 2 semi-tone pitch bend and therefore they will sound broken.

Playing in the background

Up to a little while ago the drum and melody sequencers would remain playing in the background when you were using other parts of the OPL Studio UI. However after the last round of refactoring to enable playing the various sequences in the Sequence Composer I had to disable this background playing. Now after a bit more refactoring this functionality is back again and better than before! The audio now has priority over the UI. this means that when I need to render a lot to the screen, for example when a window is opened or closed, the rendering process periodically holds briefly to allow processing MIDI and sequencer events.

Sequence Composer

What about the Sequence Composer? For now I put it on hold while I figure out how to make its very complex UI work. Dragging and dropping the sequence blocks is still a tall order, so I may go for something simpler...