picoX21H

A hybrid software/hardware simulation of the Yamaha DX21, using a Raspberry Pi Pico, a YM2151 (OPM) sound chip and an I2S DAC.

Block Diagram

Status

It’s a working musical instrument! Any of the 128 preset patches from the DX21 ROM (v1.5) can be selected and played via MIDI. Patches starting to sound like the real DX21.

Working…

• USB MIDI interface (in “peripheral” mode)
• Physical MIDI interface
• Basic integration of MIDI ins with the software synth framework
• YM2151 (OPM) driver
• PIO-based YM3012 (DAC) interface
• Captured YM3012 format samples translated to I2S (currently driving a Pimoroni Pico Audio module)
• 16x2 LCD display
• Working (but currently noisy) chorus on the Pico’s 2nd core (set MIDI CC12 >= 64)

To do…

• Verify that the YM2151 can accurately replicate the sound of the YM2164, the similar but different chip used in the DX21
• Complete the implementation of YM2151 register control from all patch parameters
• Tune and de-noise chorus
• Try adding a basic reverb on the audio path

Hardware

Schematic for the above.

See README for more information.

Software

Checkout

This repo uses git sub-modules, so checkout using –recurse to clone all the dependent source…

git clone --recurse-submodules https://github.com/SloeComputers/picoX21H.git

or

git clone --recurse-submodules ssh://git@github.com/SloeComputers/picoX21H.git

Software dependencies

• https://github.com/SloeComputers/Platform
• arm-none-eabi-gcc
• cmake via UNIX make or auto detection of ninja if installed
• Python3
• SDL2 (only for native test target)

Build

Being developed on MacOS but should build on Linux too.

Indirect build for supported targets, rpipico and rpipico2 with cmake and make (or ninja)…

make

Build a single hardware target e.g. rpipico2 using cmake…

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DPLT_TARGET=rp2350 -DCMAKE_TOOLCHAIN_FILE=Platform/MTL/rp2350/target/toolchain.cmake ..
make

flashable images will be found under the build sub-directory here…

build/Source/picoX21H_RPIPICO_I2S_DAC.uf2

License

This project is licensed under the MIT License - see the LICENSE file for details

Acknowledgements

• The engineers at Yamaha