RF64 is a custom-made bare-metal firmware for the MIDI Fighter 64 music controller. It aims to improve stability, hardware safety, performance and overall user-experience by adding commonly used features (such as full Apollo Studio support, and eventually custom color palettes).
To get started, you can grab the latest .hex file here and flash it with the official DJTT MIDI Fighter Utility app!
- @zeph (that's me!)
- Performance: Clever tricks such as parallel LED strand driving, optimized loop cycles, and zero-cost abstractions for minimal latency during the most intense lightshows.
- Boot Animation: An interactive Snake game animation that appears at boot, or after 256 seconds of idling. It stops immediately as soon as a MIDI message is received or a button is pressed, ensuring it never gets in your way.
- Keyboard Emulation: Ultra-low latency HID boot keyboard mode (ideal for rhythm games like Osu!, Geometry Dash or just general use).
- Full Apollo Studio Support: Complete FastRGB and SysEx MIDI protocol support for Apollo Studio lightshows.
- Overcurrent Protection: Built-in dynamic power scaling logic to ensure the controller never draws more than 480 mA. Not even the official firmware has this! It prevents mid-show USB port brownouts, device restarts, or thermal stress on components.
- Full Bootloader Compatibility: Easily flash back to Official Firmware (OFW) at any time using the official MIDI Fighter Utility (MFU) app.
The MIDI Fighter 64 is a boutique MIDI controller with the following specifications:
- MCU: Atmel AVR ATmega32U4
- LEDs: 128x (2x per button) WS2812B individually-addressable RGB LEDs
- Buttons: 64x SANWA OBSF-30 arcade pushbuttons
- Shift registers: 8x CD4021BM
- USB: Full-speed USB 2.0 Type-B
cargo build --releaseThis firmware uses Cargo feature flags to manage flash usage on the ATmega32U4:
| Feature Flag | Description | Default |
|---|---|---|
boot-anim |
Snake game boot animation & idle screen saver | Enabled |
apollo |
Apollo Studio FastRGB & SysEx protocol support | Enabled |
keyboard |
USB HID Boot Keyboard emulation mode | Disabled |
The ATmega32U4 has 28 KB of usable flash memory reserved for application code (4 KB is reserved for the DFU bootloader).
When compiled with opt-level = 3 (maximum speed), enabling all three features (boot-anim, apollo, and keyboard) pushes the total flash consumption from ~27 KB up to ~32 KB, which exceeds the 28 KB limit, meaning we would have to sacrifice the bootloader which is not a good idea.
While changing opt-level = "z" (size optimization) allows all features to fit into flash, it noticeably degrades high-speed LED lightshow rendering performance. opt-level = 1 results in oversized binaries, and opt-level = 2 produces results similar to level 3.
Therefore, you have two build choices depending on your priority:
- 🚀 Performance (Recommended): Keep
opt-level = 3and use default features (boot-anim+apollo, nokeyboard). - 🎹 Features: Set
opt-level = "z"inCargo.tomland build with--features keyboardif keyboard emulation is required:
cargo build --release --features keyboardNote
Before you flash this, please be aware:
This project is community-made firmware. While it will not brick your MF64, don't try flashing it if you're not sure of what you're doing. As this is open-source software licensed AGPL-3.0, friendly reminder that you are taking full responsibility. DJTT's official firmware works great, too!
Additionally, this firmware does not have the capability to permanently destroy your device; in the worst possible case that the flashing process goes wrong and you're left with just the bootloader, a technician can always recover the MCU via ICSP (In-Circuit Serial Programming).
This fragility is a fundamental limitation of DJTT's LUFA bootloader, and would require a custom bootloader (plus ICSP to rewrite it), in order to fix.
There's actually two ways to flash the firmware, depending on whether you want to use the built-in bootloader or not.
Connect the wires as follows (you can pick your favorite colors, these are just what I like):
| Pin | Function | Color |
|---|---|---|
| 1 | MISO | Blue |
| 2 | VCC | Red |
| 3 | SCK | White |
| 4 | MOSI | Green |
| 5 | CS/RST | Yellow |
| 6 | GND | Black |
Then run the following command:
# This will load the bootloader first...
avrdude -c buspirate -p atmega32u4 -U flash:w:bin/BootloaderDFU_mf64.hex
# ...and then the actual firmware, using -D to disable auto-erase.
avrdude -c buspirate -p atmega32u4 -D -U flash:w:target/rf64.binYou may also use an Arduino, a Raspberry Pi (make sure to step-down the 5V GPIO to 3.3V or the Raspberry might suffer!), or any other programmer that supports the AVR family. DJTechTools used an usbtiny programmer.
With the built-in DFU bootloader, things get 10x easier.
Caution
There is a catch: it is very easy to soft-brick your controller if you disconnect the USB cable between the erase and flash commands.
This is because the bootloader only starts if a specific value is written in RAM. Powering off the device without a valid firmware will reset the device, thus the magic value will get wiped and the bootloader will never start again. You will then need to use the ICSP header to re-flash the device completely.
Always finish flashing before removing the USB cable or using start to reboot the device.
To flash a new firmware, you'll first have to start the MF64 in DFU bootloader mode.
- Unplug it, if you haven't already
- Press the button on the very bottom-left
- While keeping the button pressed down, plug the MF64's USB back in and wait 2 seconds
If everything went correctly, in your devices you should now see something like "Midi Fighter DFU Bootloader".
Open the app, go to the top and select Tools -> Load custom firmware -> for a 64 and pick the .hex file you downloaded from here.
💻 Using the dfu-programmer terminal utility
Download a prebuilt binary for the dfu-programmer utility, and then run:
# ! DO NOT UNPLUG THE DEVICE IN-BETWEEN THESE !
# Replace `target/rf64.hex` with the path to your downloaded `.hex` file
dfu-programmer atmega32u4 erase
dfu-programmer atmega32u4 flash target/rf64.hex
# ONLY AFTER FLASHING, optionally, to reboot the device:
dfu-programmer atmega32u4 startTo rollback using the MIDI Fighter Utility, you must manually boot into DFU bootloader mode (hold bottom-left button on startup). The MFU app will intentionally not detect the device in normal operating mode to prevent it from issuing unsupported OFW commands (such as saving custom color profiles).
You will then see an orange checkerboard pattern on your device. This indicates you successfully entered bootloader mode. Simply open the MFU app now, select 64 from the list of devices (this is REALLY important) and wait patiently.
Caution
Do not disconnect the device until you see the DJTT boot animation.
Follow standard safety guidelines when flashing low-level firmware (don't use a janky cable, don't use a USB hub, close all apps that may interfere...)
I've solo-built this project, but I would've never been able to do it without:
- DJTechTools and Shawn Wasabi for creating the MIDI Fighter 64 and (maybe indirectly) releasing the original firmware source code. Most of the startup code in this project is a literal 1:1 translation, because we cannot improve the bits that are perfect.
- The Rust Embedded Working Group and the avr-rust people, which allows us to compile Rust code for AVR microcontrollers.
- Anth for bits of advice on the MF64's hardware, bootloader and firmware.
And lastly, our beloved Gemini and Claude for literally carrying this during the black-box debugging of this project.
This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0).
What this means:
- ✅ You can use this firmware to build other open source things.
- ✅ You can modify the firmware to suit your needs.
- 🛑 You cannot use this code for network services (although I really doubt you're going to do much with a firmware)
- 🛑 If you distribute modified versions of this firmware, you must provide the source code as well.
See LICENSE for more details.