Dexed is a FM synthesizer closely modeled on the famous DX7 by a well-known Japanese manufacturer. MiniDexed is a port to run it on a bare metal Raspberry Pi (without a Linux kernel or operating system). Currently it is not functional yet. Contributions are highly welcome.


Contributions are highly welcome.

  • Get Dexed to build with circle-stdlib
  • Upload SD card contents to GitHub Releases
  • Get it to run on a Raspberry Pi 4 without crashing
  • Get it to produce some sound on the headphone jack
  • Get it to react to USB MIDI
  • Get it to react to MIDI via Raspberry Pi 4 GPIO
  • Get 8 Dexed instances to run simultaneously (like in a TX816) and mix their output together
  • Add functionality for loading .syx files (e.g., from
  • Add a way to configure each Dexed instance
  • Allow for each Dexed instance to be stereo shifted
  • Add reverb effect

I am wondering whether Dexed could be ported to Circle, in order to recreate basically an open source equivalent of the TX802 (8 DX7 instances without the keyboard in one box).


  • Download from GitHub Releases
  • Unzip
  • Put the files into the root directory of a FAT32 formatted partition on microSD card
  • Boot in Raspberry Pi 4

Building locally

E.g., on Ubuntu 20.04:

git clone
cd MiniDexed

# Recursively pull git submodules
git submodule update --init --recursive

# Install toolchain
wget -q
tar xf gcc-arm-*-*.tar.xz 
export PATH=$(readlink -f ./gcc-*/bin/):$PATH

# Build circle-stdlib library
cd circle-stdlib/
./configure -r 4 --prefix "aarch64-none-elf-"
make -j$(nproc)
cd ..

# Build MiniDexed
export PATH=$(readlink -f ./gcc-*/bin/):$PATH
cd src
make -j$(nproc)
ls *.img
cd ..

# Get Raspberry Pi boot files
cd ./circle-stdlib/libs/circle/boot
make armstub64
cd -

# Make zip that contains Raspberry Pi 4 boot files
mkdir -p sdcard
cp -r ./circle-stdlib/libs/circle/boot/* sdcard
mv sdcard/config64.txt sdcard/config.txt
rm -rf sdcard/config32.txt sdcard/README sdcard/Makefile sdcard/armstub sdcard/COPYING.linux
cp ./src/*img sdcard/
zip -r sdcard/*



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