MiniDexed Raspberry Pi V1 IO Board

Advanced, PCB Design, Synth Modules 2 Minutes

I already have two different IO boards for use with MiniDexed on a Raspberry Pi and whilst MiniDexed works best on a Pi 3 or 4, providing 8 full DX7-compatible tone generators, it is also possible to run it on a V1 Raspberry Pi, although it is limited in performance to a single tone generator.

This PCB provides MIDI, DAC, screen and controls for a Pi V1 based MiniDexed synthesizer.

The build guide is available here: MiniDexed Raspberry Pi V1 IO Board – Part 2

RPi-V1-MiniDexed-IOBoard-3d

Warning! I strongly recommend using old or second hand equipment for your experiments.  I am not responsible for any damage to expensive instruments!

These are the key tutorials for the main concepts used in this project:

If you are new to microcontrollers and single board computers, see the Getting Started pages.

The Circuit

RPi-V1-MiniDexed-IOBoard-sch

All of the elements in this circuit have been met before, so I won’t go into the details again.

Here are some of the key points and the previous information:

PCB Design

RPi-V1-MiniDexed-IOBoard-pcb

The design is very similar to my previous SSD1306 MiniDexed IO board but naturally has to use a board with a physical footprint for the V1 Pi.  I’ve used a dual footprint for the MIDI sockets so that either 5-pin DIN and TRS sockets could be used.

It also needs to interface to the additional P5 header as that is the only way to get hold of the I2S interface for the PCM5102 DAC.

This is the GPIO map being used:

  • GPIO00,01 – I2C for the display
  • GPIO22,27 – Switches
  • GPIO9,10,11 – Rotary encoder
  • GPIO14,15 – TX and RX for MIDI
  • GPIO28,29,30,31 – I2S interface on P5

RPi-V1-MiniDexed-IOBoard-ger

Closing Thoughts

This sort of “completes the set” for me now – I now have a range of MiniDexed boards that all seem to be quite useful as “stand alone units”.

I might revisit this one day to think about something useful in a pi Zero form factor, but that would probably be all for now (especially as I’ve now built my TX816 version!).

These boards have been manufactured using the Seeed Fusion PCB service, which I am happy to continue to recommend. They have been supported with discount vouchers that I’ve been sent by Seeed for my previous projects.

Kevin

Published by Kevin

Just another soul meandering my way around the Internet ...

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7 thoughts on “MiniDexed Raspberry Pi V1 IO Board”

    1. I don’t have them for sale I’m afraid, but if you can get me an email address privately (diyelectromusic at gmail should get to me) so we can share details, then I have some spares and we can negotiate! 🙂

      Update: the design and build guides have just been published, and all seems ok – so do give me a shout if you’re still interested.

      Thanks for showing me your piezo MIDI controller! It looks great and those are very effective sounds you’re using with it 🙂

      Kevin

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  2. Hi! I’m just wondering if this will work with the original v1 https://www.etechnophiles.com/raspberry-pi-1-gpio-pinout-schematic-and-specs-in-detail/ I’ve tested minidexed on these ( I have a bunch to reuse) as well as the b+ and zero types. I’d just use your gerbers and have a couple made but on the v1 the headers (p2 & p3) are labeled differently, though I think it’s the same layout?

    Thanks for your great series of articles!

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    1. It should work with any Pi that has a P5 connector for the I2S interface. Without that I guess it would still work just without the DAC? On some versions of the V1 Pi GPIO 27 was GPIO 21 so it might need a different pin configuration in minidexed.ini, and I2C was different too, so I don’t know if that would work or not – but if you have some already that should be easy to try using jumper wires…?

      Kevin

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  3. I just double checked your board and my pis. I’ve ordered some PCBs. I’ll have some extras should anyone enquire.

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