Vintage B&O,
modern / streams.

MDTv2 is a stacking HAT for the Raspberry Pi. Plug it on, attach an ML or DL cable, power up. That's it. Three things make it work:

Bi-directional audio

Studio-grade 24-bit DAC and ADC handle audio in and out. They drive MasterLink's symmetric audio pairs natively (no analog switches, no op-amp stages), and they cover DataLink's single-ended line-level audio on the same board. The audio side is HiFiBerry DAC+ADC Pro compatible, so it appears to Linux as a standard sound card with stereo input and output. shairport-sync, Spotifyd, mpd, your own scripts: anything just works.

Onboard MCU · serial bridge

The big change in v2: a dedicated microcontroller on the board handles the messy parts of MasterLink and DataLink: the unusual framing, the weird voltage levels, the timing. Your software just reads and writes plain serial messages over the Raspberry Pi's GPIO UART. Nothing to wire up, no extra USB cable, no driver tricks. Send "skip track" as a one-liner; receive now-playing metadata as a string.

Transparency mode · zero-config audio

There's a catch the audio path can't solve on its own: the vintage B&O system has to be told over MasterLink that audio is playing, otherwise it stays in standby and the audio port is silent. Normally that's the job of the ml-tools stack you set up on the Pi.

The MCU firmware short-circuits this with a built-in transparency mode. It watches the audio bus on its own, and the moment Linux starts streaming audio without a matching ML command, it automatically sends a generic power-on telegram to open the audio port. You won't get metadata or granular control this way (that still needs ml-tools), but the audio itself plays through with zero software configuration, on any Raspberry Pi OS, out of the box.

Standard connectors

RJ45 for MasterLink (with an included ML ↔ RJ45 adapter that works with any shielded Ethernet cable), 7-pin DIN for DataLink. Stacks onto the Pi's 40-pin GPIO header. Comes with a 3D-printed housing.

MasterLink is B&O's second-generation multi-room bus. Introduced in the early 1990s, it replaced DataLink and stayed in production until around 2014. It carries symmetric bi-directional line-level audio alongside a low-voltage data channel, all on the same connector, a real engineering feat for its era.

What you can do with it

• Stream into a music system as a native source. Appears as N.Radio / N.Music with metadata on the display.
• Capture audio from the music system (CD, tuner, etc.) and redistribute over IP.
• Drive standalone link speakers like the BeoLab 3500 / 2000 directly: auto power-on, clock sync, full remote control.
• Forward Beo4 remote presses to your own scripts to control whatever you like (a modern TV, smart-home routines, etc.).
• Read everything happening on the bus (live now-playing, source changes, transport state) as plain serial messages.

How it shows up in software

The onboard MCU bridge converts the MasterLink wire protocol into a clean line-based serial stream on the Pi's UART. Open /dev/serial0 in any language, write commands as text, read events as text. The ml-tools package wraps that with a Redis pub/sub broker and a handful of ready-made services (link-speaker emulator, source-provider, remote forwarder).

Connector

Original MasterLink used a 16-pin Molex connector that's still available but expensive. MDTv2 ships with a passive ML ↔ RJ45 adapter that plugs into any ML socket and accepts standard shielded CAT cable. Extra adapters and a passive RJ45 distributor (for chaining multiple ML devices) are available separately.

DataLink was B&O's interconnect standard before MasterLink arrived (around 1980 to early 90s). MDTv2 supports the variants that matter today: Audio Aux Link / DL'86 for music systems and TVs, and DL'80 for standalone peripherals (turntables, CD players, cassette decks).

What you can do with it

• Inject streaming audio into the music system over the Aux Link, with auto power-on and remote control respected.
• Pull audio out of brick-era systems (BC9500, BS6500/7000) for distribution to modern AirPlay speakers.
• Connect a vintage turntable directly (BeoGram 4500 / 6500 / 7000) for IP-streaming of standalone tangentials with full transport control.
• Bridge Beo4 IR commands to whatever modern target you want.

How it shows up in software

Same as MasterLink: the onboard MCU bridge handles the DataLink line code and exposes everything as plain serial messages on the Pi's UART. The dl-tools package provides a Redis pub/sub broker plus reference services on top.

What's in the box

• MasterDataTool PCB assembly
• 3D-printed housing (three plastic parts + 8 screws)
• ML ↔ RJ45 plug-in adapter
• Short manual / quick-start card

What you'll need separately

• A Raspberry Pi (model 2, 3, 4 or 5)
• A microSD card for the OS
• A power supply (we recommend the official Raspberry Pi PSU)
• An RJ45 cable to connect MDTv2 to your B&O device. Must be shielded (look for visible metal on the connector). Standard plastic-clad CAT cables won't carry the MasterLink signal reliably.

1. Assemble

1. Drop the Raspberry Pi into the larger plastic shell.
2. Hold the small plastic frame against the top of the Pi and insert four screws from the bottom.
3. Plug the MDTv2 PCB onto the Pi's 40-pin GPIO header.
4. Fit the top plastic part and secure it with the remaining four screws.

2. Flash the operating system

We recommend Raspberry Pi Imager. Choose your Pi model and pick Raspberry Pi OS Lite (under "Other"). Click Next → Edit Settings and:

• Set a custom hostname you'll remember
• Enter a username and password
• Enable wireless LAN and add credentials (unless you'll use Ethernet)
• Pick the correct timezone and region
• Go to the Services tab and enable SSH with password authentication

Save, write, and wait for the flash to complete.

3. First boot

1. Insert the microSD into the Pi + MDTv2 stack.
2. Attach the ML or DL cable to the target vintage device.
3. Power up the Pi and wait for it to appear on your network.

4. SSH in and run the one-line installer

SSH in:

ssh your_username@your_hostname.local

Then run the mdtv2-tools bootstrap. It installs git, clones the repo into /opt/mdt-tools-src/, then hands off to install.sh which sets everything up: apt dependencies (Redis, shairport-sync, …), boot-config patches to free /dev/serial0, kill HDMI audio, and load the DAC+ADC overlay, both systemd services (mdtv2-broker and ml-source-bridge), and a hidden Python venv for the MCU updater.

curl -sSL https://gitlab.com/masterdatatool/software/mdtv2-tools/-/raw/master/bootstrap.sh | sudo bash

The installer is idempotent — re-run it any time to pick up the latest master. If you'd rather inspect the script first, omit | sudo bash and read it.

5. Configure the bridge

The bridge reads /etc/ml-source-bridge.toml. On first install the default config claims N.RADIO as an AirPlay source, in Source Center mode. Edit to match your setup:

sudo $EDITOR /etc/ml-source-bridge.toml

Common things to change:

• role — "sc" (Source Center, alongside a real Audio Master) or "am" (Audio Master emulation for setups without one).
• [[sources]] — which ML source byte we claim (0x7A = N.MUSIC, 0xA1 = N.RADIO, …) and the display name shown on B&O front panels.
• [light_handler] — optional. Maps Beo4 LIGHT + <key> combinations to arbitrary shell commands (Home Assistant calls, MQTT publishes, GPIO toggles, …). See the comments in the file for the full Beo4 key name table.

Apply changes by restarting the bridge:

sudo systemctl restart ml-source-bridge.service

6. Stream something

shairport-sync is already installed and ready. Pick your Pi from any AirPlay-capable device's output menu and start playing. MDT will auto-wake the connected ML system, forward track and artist metadata, and hand playback control (next, previous, standby) back to the original remote.

Follow the live log to see what's happening:

sudo journalctl -u mdtv2-broker.service -u ml-source-bridge.service -f

7. Update the MCU firmware (optional)

The MDT HAT ships pre-flashed, but if you ever need to update:

sudo /opt/mdt-tools/mcu-firmware/flash.sh \
     /opt/mdt-tools/mcu-firmware/firmware-v1.5.5.hex

The script toggles the UART selector, stops the broker, runs pymcuprog, then restarts everything. No manual venv juggling.

Where to go from here

The software is in early-alpha territory. Every scenario we ship works for us, but the corner cases are many. ml-debug and dl-debug (in /opt/mdt-tools/) give you a real-time decoded view of every MasterLink and Datalink message on the bus — they're the first tools to reach for when something isn't behaving:

# MasterLink
sudo python3 /opt/mdt-tools/ml-debug/ml_debug.py

# Datalink ('80 and '86 combined)
python3 /opt/mdt-tools/dl-debug/dl_debug.py

The broker exposes a Redis interface (link:ml:*, link:dl80:*, link:dl86:*, link:gpio:*), so wiring up custom automations on top is trivial — see the example DL scripts at /opt/mdt-tools/dl-scripts/ for ready-to-use recipes (Beogram turntable control + 60 s phono capture to FLAC, BeoCenter / BeoMaster CD control + line-level capture).

What's planned

• Pre-configured ML and DL scenarios (link-speaker emulation, source provision, audio injection, remote forwarding), all running out of the box, no commands to type.
• Web configurator: open the Pi's IP in a browser, point and click your way through which mode you want and which streaming services to enable.
• All the popular streaming back-ends bundled and pre-wired: shairport-sync (AirPlay), librespot (Spotify Connect), Lyrion (Logitech Media Server), Roon Bridge, and more.
• Tiny installer image, self-updating thereafter. Flash a small bootstrap SD card once. On first boot it pulls the real OS from our servers and installs it; from then on it keeps itself updated automatically.
• Made for users without embedded Linux experience: no SSH, no apt-get, no /boot/config.txt. If you can flash an SD card and open a webpage, you can run MDT-OS.