OpenX32

This repository contains software to load and start the Linux-Kernel on the Behringer X32, some userland tools and x32ctrl - the main logic of our custom firmware. This audio-mixing-console uses a Freescale/NXP i.MX253 Microcontroller with an ARM926EJ-S core that supports booting Linux.

Currently the Linux Kernel is running in Version 6.18 (LTS) with busybox (the picture is older, shows Kernel 6.12):

x32ctrl is the new GUI and program that controls the individual boards and devices:

Since the beginning in May 2025 the UI has improved a bit and some of the original X32-functions are already implemented in OpenX32:

You can find more information in the two related Youtube-Videos:

A Youtube Short of the complete OpenX32 Alpha running on a X32 Rack:

What is working at the moment and what is planned so far

Next to the underlaying Linux we are working on the audio-processing as well.

The Linux has control over most parts of the i.M253 main-controller:

• [x] Linux-Kernel in Version 6.18 (LTS) starts to shell using 800x480 display framebuffer
• [x] init-script for setting up the operating system
• [x] MIDI-Input and -output is used as an additional serial-port-terminal (see pinout down below)
• [x] Support of 100MBit ethernet network-support with DHCP
• [x] Support of internal Realtime-Clock
• [x] Support of USB-Host interface (HID-Keyboard, HID-Mouse, Mass-Storage-Devices, Joystick, Soundcard, etc.)
• [x] Support of internal SD-Card to read MAC-Address and the general configuration

Most audio-functions are already supported:

• [x] Configuration of FPGA (Xilinx Spartan 3A or Lattice ECP5) via internal SPI-interface
• [x] Support of both AnalogDevices DSPs (ADSP-21371 SHARC DSPs) via internal SPI-interface
• [x] Support of 1:1-routing for the available 112 inputs (32x XLR, 8x AUX, 32x Card, 40x DSP) to 112 outputs (16x XLR, 16x UltraNet, 8x AUX, 32x Card, 40x DSP)
• [x] Support of UltraNet-Output
• [x] Support of internal 8-channel analog input- and output-cards including headamp- and phantom-power-control
• [x] Support of internal 8-channel AUX-AD/DA-Converter (CS42438 on older revisions, M8000 on newer revisions)
• [x] Noisegate, 4-band EQ and compressor per channel is already working within the main-DSP
• [x] Some more advanced audio-algorithms are already implemented in DSP2
• [x] AES50 is working on Lattice-FPGA-versions. Receiving and sending audio and using the AUX-channel for headamp-control is working.

The hardware-surface is working, too:

• [x] Support of booting from SD-Card and via USB using the original DCP-Bootloader
• [x] Control of X32 surface (faders, buttons, LEDs, encoders) through x32ctrl-software

So the most important things (audio in/out, control-surface, display) are working already and more things are on the ToDo-list:

• [ ] In-Progress: Boot from barebox as a successor of U-Boot (U-Boot has ended the support of i.MX25 since a couple of years; barebox already boots OpenX32 from development sd-cards)
• [ ] Planned: ALSA Soundcard with I2S to main-FPGA (DeviceTree option "simple-audio-card" via SSI1 and AUDMUX is not initializing)
• [ ] Planned: GPIO support via libgpiod (at the moment libgpiod is not working and has no control over /dev/gpiochipX)

LVGL v9.5.0 is running on the X32 with a good performance (30 fps). So this will be a basis for this open-source Operating System:

What's the reason for developing such a thing?

I want to learn things about embedded systems and how they work. The X32 is a very powerful playground with lots of different controllers, nice faders and displays. So that's the only reason why I'm doing this :-)

Is there a Community Forum to get in touch and talk about all this nice stuff?

Yes, here: https://discourse.openmixerproject.de

Steps to run OpenX32 without recompiling

Checkout the most recent release from https://github.com/OpenMixerProject/OpenX32/releases and follow the instructions there. You only have to copy a couple of files onto an USB-thumbdrive and boot into Linux :)

Steps to compile the new operating system

Step 1: Init Git-Submodules and install dependencies

This system uses the most recent versions of the tools I could find: the bootloader u-Boot is used in Version 2020.10 as this is the last U-Boot supporting the i.MX25. Up to now Linux has still support for the i.MX25 and I selected v6.12, the most recent LTS-kernel.

So the repository uses other GitHub-repositories as submodules (u-Boot, Linux and pyATK). Please use the following command to checkout the main-repo together with submodules. To minimze the download-size and -time, we will clone the submodules separately:

git clone --depth 1 https://github.com/xn--nding-jua/OpenX32.git
cd openx32
./gitinitsubmodules.sh

Next to the sourcecode, your system needs to be setup correctly to compile the whole system: setup your debian-based system by calling:

./setup.sh

This script will install several dependencies to compile u-boot and the linux-kernel. After installing the packets, it will patch pyATK to run with recent versions of Python 3.11 and newer. It will also configure pyATK in a virtual python-environment.

Step 2: Run the scripts

Compile u-boot, Linux and busbox by calling the script ./compile_all.sh and upload the new operating system into the RAM by calling the script ./run.sh

./compile_all.sh
./run.sh

• compile_all.sh will copy some patched files into the submodules, compile a small program called "miniloader", the U-Boot-bootloader and the Linux kernel. The kernel-image "zImage" will be converted to a "uImage" and will be merged together with the miniloader and u-boot-image into a single binary-file.
• Finally, run.sh will use pyATK to initialize the most important hardware of the i.MX253 using the file "meminit.txt" and upload the generated binary-blob into the RAM of the processor. The Serial-Download-Program of the i.MX will then start the small assembler-program "miniloader" placed at address 0x80000000 - hence the begin of the RAM. The only task of Miniloader is to jumpstart the U-Boot-Bootloader at offset 0x3C0. U-Boot is placed at offset 0x0C0, but the first function-entry of the U-Boot will not start when using the Serial-Download-Program. So with this small hack, U-Boot takes control over the i.MX, reallocate itself to a higher memory-region and starts the linux-kernel together with the DeviceTreeBlob. The kernel is then decompressed and will start up.

Step 3: Compile user-softwares

Within the software-folder several user-applications are placed. You can call the script "compile_software.sh" to compile all softwares at once or compile them individual:

• x32ctrl: call "make". The binary is copied to the folder "../bin/"
• x32sdconfig: call "compile.sh". Program will read the original SD-card on boot and put general information about the board to the folder /etc/

There are some test-softwares in the "test"-folder. Use individual "compile.sh" scripts

• fpgaconfig: program to configure the Xilinx Spartan 3A FPGA using spidev2.0
• dspconfig: program to configure the two AnalogDevices 21371 SHARC DSP using spidev0.0 and spidev0.1
• spiread: program to test the communication to the DSPs
• uarttest: program to test communication with FPGA

As the X32 has limited RAM available, you might use the script "build_distribution.sh" to copy all important files into the folder "usb". Then take an USB-Thumbdrive, copy all files within this folder to the root of the USB-drive and mount the device on the X32 with the command "mount /dev/sda1 /mnt/usb".

Now run the script "/mnt/usb/scripts/startall.sh". This will create important Symlinks to the main-system and start an SSH-Server.

Important: at this early development stage, some packages, libraries or other things will be missing. Please create a ticket in GitHub so that I can fix this.

Step 4: Compiling logic for the FPGA

The X32 devices before 2020 are using a Xilinx Spartan-3A X3CS1400 FPGA to route the audio between the individual ADCs, DACs, expansion card and digital connectors like AES50 and UltraNet. For the Spartan-3A we can use the free version of Xilinx ISE 14.7 as the most recent toolchain to synthesize logic for this FPGA:

Download ISE 14.7 from the Xilinx (AMD) website: https://www.xilinx.com/support/download/index.html/content/xilinx/en/downloadNav/vivado-design-tools/archive-ise.html. There are two options: a preinstalled linux virtual machine or the direct version. The virtual machine is working fine. If you want to use the direct version under Windows, here is a short manual as this needs some adjustments:

1. Download the DVD image: https://www.xilinx.com/member/forms/download/xef.html?filename=Xilinx_ISE_DS_14.7_1015_1.tar
2. Start the setup and install the software (the setup will take a loooong time). Between 93% and 95% the installation will hang: go into the taskmanager and kill the software "Webtalk32.exe" and "xwebtalk.exe" several times until the setup finishes (successfully!)
3. Set the Windows-Environmental-Variable "XILINX_VC_CHECK_NOOP" to "1". Otherwise the software will complain about a non-installed VisualStudio Runtime 2008 even if it is installed correctly
4. On modern Windows 10/11 ISE 14.7 will not start beyond the Splash-Screen due to the use of "SmartHeap" within the file "libPortability.dll". Download a hotfix from https://