Having now found a way to use a Raspberry Pi Zero as a DX7 USB Dongle in a "headless" capacity I thought it would be useful to have a version of my MiniDexed Raspberry Pi IO Board suitable for use with the Zero.
Warning! I strongly recommend using old or second hand equipment for your experiments. I am not responsible for any damage to expensive instruments!
If you are new to microcontrollers and single board computers, see the Getting Started pages.
The Circuit
This is essentially the same schematic as my MiniDexed Raspberry Pi IO Board but without the MIDI interface section. Consequently it supports the following:
- SSD1306 128x32 display (I2C).
- Back and Home buttons (GPIO 5 and GPIO 6).
- Rotary encoder (GPIO 9, 10, 11).
- GY-PCM5102 module (I2S).
The PCM5102 module is optional and an alternative I2S DAC could be used instead, such as the Pimoroni Audio DAC SHIM I used on my DX7 USB Dongle.
Also, as I'm thinking this will be most useful as a dongle, I've not attempted to include serial MIDI circuitry, assuming USB MIDI is the most likely option to be used.
PCB Design
I opted to leave MIDI off this board in order to give me the best chance to fit everything else in. The PM5102 is optional. If fitted, then the SSD1306 will have to be raised to sit slightly above it.
I've noticed on mistake on the board. All the "debouncing" capacitors for the encoder and switches are labelled 10p where that should be 10n. For some reason I keep doing that! And I know I have another board currently being made that has the same mistake.
Apart from that, there isn't a lot else to say for this one.
Closing Thoughts
I have another board on the way that provides MIDI as a stackable option, but for the focus of this one - a simple UI for MiniDexed - I think this should do the job.
Kevin
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