Home Assistant MQTT Bridge for RME ADI-2 DAC

Disclaimer: This project is an independent open-source software and is not affiliated with, endorsed by, or in any way officially connected to RME Audio (Audio AG) or any of its subsidiaries or affiliates. The official RME Audio website can be found at https://www.rme-audio.de. The name "RME" as well as related names, marks, emblems, and images are registered trademarks of their respective owners.

Control your RME ADI-2 DAC Line Out volume via Home Assistant. A Raspberry Pi handles volume control directly in the DAC hardware (not digitally!) via USB-MIDI, detects online/offline status, and communicates everything over MQTT.

Important: This bridge controls Line Out volume only (not headphone output or input selection). The USB connection is used exclusively for MIDI control – audio can come from any source.

Quick Start

git clone https://github.com/Cha40s/homeassistant-bridge-for-rme.git
cd homeassistant-bridge-for-rme
sudo ./install.sh

The script installs all dependencies, prompts for MQTT credentials, and starts the service.

Highlights

Volume control directly in the DAC via USB-MIDI SysEx (no digital clipping)
Home Assistant integration via MQTT (slider, presets, automations)
Safety limits: hard boundaries at -60 dB to -10 dB
DAC online/offline detection with delayed initialization
Default volume on power-up with retries until USB-MIDI is stable
Graceful shutdown on SIGTERM (clean MQTT disconnect)
Optional: Spotify Connect (raspotify) with DAC-controlled start/stop

Hardware

Component	Tested with
Raspberry Pi	Pi 4, Pi 5 (any model with USB should work)
DAC	RME ADI-2 DAC FS
USB cable	Standard USB-A/C to Micro-B
OS	Raspberry Pi OS (Bookworm), DietPi, Debian 12/13
MQTT Broker	Mosquitto (e.g. on Home Assistant)

Note: The RME ADI-2 DAC registers as both a USB audio and USB MIDI device. The bridge only uses the MIDI interface for volume control. Audio runs separately.

Audio Source Setup

The bridge controls volume regardless of how audio reaches the DAC. You need to set the correct DAC input to match your setup:

Audio source	Connection	DAC input setting
External player (WiiM Mini, CD, streamer)	SPDIF optical/coax to DAC	Set DAC to SPDIF or Optical
This Raspberry Pi (raspotify / Spotify Connect)	USB to DAC (shared with MIDI)	Set DAC to USB

The installer will ask which setup you use and install raspotify automatically if needed.

Why SPDIF is enough

The RME ADI-2 DAC's USB input is technically superior to SPDIF (higher sample rates, native DSD, async transfer). However, these advantages only matter with hi-res source material beyond CD quality. Spotify's highest tiers top out well within SPDIF's capabilities:

Spotify quality	Format	Bitrate
Normal	OGG	~96 kbit/s
High	OGG	~160 kbit/s
Very high	OGG	~320 kbit/s
Lossless	FLAC	up to 24-bit/44.1 kHz

Even Spotify Lossless at 24-bit/44.1 kHz is handled perfectly by SPDIF (which supports up to 24-bit/192 kHz). There is no audible difference between USB and SPDIF when the source is Spotify – at any quality level.

This means you can use an affordable network streamer like the WiiM Mini via SPDIF and keep the USB port free for MIDI control only. The WiiM Mini supports Spotify Connect, AirPlay, and Chromecast at a fraction of the cost of high-end streamers – a perfect match for this setup.

Signal Flow

Files

File	Purpose
`rme_mqtt_bridge.py`	Main bridge: MQTT ↔ USB-MIDI, DAC detection, volume logic
`rme-mqtt-bridge.service`	systemd service for the bridge
`env.example`	Template for `/etc/default/rme-mqtt-bridge` (credentials + options)
`install.sh`	Automated setup script
`raspotify_manager.py`	Optional: start/stop raspotify based on DAC status
`raspotify-manager.service`	systemd service for the raspotify manager
`conf`	Example `/etc/raspotify/conf` (librespot, bit-perfect)

Prerequisites

Raspberry Pi with USB connection to the RME ADI-2 DAC
MQTT broker (e.g. Mosquitto on Home Assistant)
Python 3.10+ and paho-mqtt (installed automatically)
amidi from alsa-utils (installed automatically)

Installation

Automatic (recommended)

git clone https://github.com/Cha40s/homeassistant-bridge-for-rme.git
cd homeassistant-bridge-for-rme
sudo ./install.sh

Manual

Install dependencies

sudo apt update
sudo apt install python3 python3-paho-mqtt alsa-utils

Create MQTT credentials file

sudo cp env.example /etc/default/rme-mqtt-bridge
sudo chmod 600 /etc/default/rme-mqtt-bridge
sudo nano /etc/default/rme-mqtt-bridge   # Set MQTT_USER and MQTT_PASS

Install bridge

sudo cp rme_mqtt_bridge.py /usr/local/bin/
sudo chmod +x /usr/local/bin/rme_mqtt_bridge.py
sudo cp rme-mqtt-bridge.service /etc/systemd/system/

Adjust service file (if needed)

sudo nano /etc/systemd/system/rme-mqtt-bridge.service
# Adjust MQTT_HOST, MIDI_PORT etc.

Start

sudo systemctl daemon-reload
sudo systemctl enable --now rme-mqtt-bridge

Optional: Raspotify (Spotify Connect)

If you chose option 2 (USB audio) during installation, raspotify is already set up. For manual installation:

sudo apt install raspotify
sudo cp conf /etc/raspotify/conf
sudo cp raspotify_manager.py /usr/local/bin/
sudo chmod +x /usr/local/bin/raspotify_manager.py
sudo cp raspotify-manager.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now raspotify raspotify-manager

The raspotify manager automatically starts/stops raspotify when the DAC goes online/offline. Audio is streamed bit-perfect (S32, 320 kbps), volume is controlled in the DAC (not digitally). Make sure the DAC input is set to USB.

DietPi Notes

DietPi uses systemd (since v6), service files work out of the box
ALSA utils: sudo apt install alsa-utils or via dietpi-software
Audio device issues: check dietpi-config → Audio options
SSH access is enabled by default on DietPi (user: root)

MQTT Topics

Topic	Direction	Payload	Description
`rme/lineout/db/set`	Subscribe	Float dB (e.g. `-43.5`)	Desired volume
`rme/lineout/db/state`	Publish (retained)	Float dB	Actual volume set
`rme/dac/status`	Publish (retained)	`online` / `offline`	DAC detection via `amidi -l`
`rme/bridge/status`	Publish (retained, LWT)	`online` / `offline`	Bridge status

Home Assistant Example

mqtt:
  number:
    - name: "ADI-2 Line Out Volume"
      command_topic: "rme/lineout/db/set"
      state_topic: "rme/lineout/db/state"
      availability_topic: "rme/dac/status"
      payload_available: "online"
      payload_not_available: "offline"
      min: -60
      max: -10
      step: 0.5
      unit_of_measurement: "dB"
      mode: slider
      optimistic: true

Slider for Volume Control with Bubble-Card

  - type: custom:bubble-card
    card_type: button
    button_type: slider
    entity: number.adi_2_line_out_volume
    name: Spotify Volume
    icon: mdi:music
    show_icon: true
    scrolling_effect: true
    show_name: true
    show_state: true
    show_attribute: false
    min_value: -60
    max_value: -10
    step: 0.5
    tap_to_slide: true
    relative_slide: false
    slider_live_update: false
    slider_value_position: right
    invert_slider_value: false
    tap_action:
      action: none
    double_tap_action:
      action: none
    hold_action:
      action: none
    card_layout: normal
    sub_button:
      main: []
      bottom: []

Automation for RME Autostart with Broadcom Remote

alias: "Auto-Start: RME DAC bei Musik"
description: Schaltet RME DAC ein, wenn Wohnzimmer 2 spielt, aber DAC noch aus ist.
triggers:
  - entity_id: media_player.wohnzimmer_2
    to: playing
    trigger: state
conditions:
  - condition: state
    entity_id: binary_sensor.rme_dac_status
    state:
      - "off"
actions:
  - action: remote.send_command
    data:
      device: RME
      command: power
    target:
      device_id: c68222ed90bed75eb7b8a38bc1ed133a
mode: single

Configuration

All settings can be set via environment variables – either in the service file or in the EnvironmentFile (/etc/default/rme-mqtt-bridge).

Variable	Default	Description
`MQTT_HOST`	`192.168.100.60`	MQTT broker address
`MQTT_PORT`	`1883`	MQTT broker port
`MQTT_USER` / `MQTT_PASS`	empty	MQTT auth (via EnvironmentFile)
`MIDI_PORT`	`hw:1,0,0`	ALSA MIDI port of the DAC
`DEFAULT_DB`	`-50.0`	Volume applied on DAC ready
`MIN_DB` / `MAX_DB`	`-60.0` / `-10.0`	Hard limits
`DAC_POLL_SECONDS`	`1.0`	DAC detection poll interval
`READY_STREAK`	`3`	Consecutive online polls before "ready"
`APPLY_RETRIES`	`6`	Retries when setting volume
`APPLY_RETRY_DELAY`	`0.6`	Seconds between retries
`DEBOUNCE_SECONDS`	`0.03`	Minimum interval between updates
`DEBUG`	`0`	Set to `1` for verbose logging

Troubleshooting

DAC not detected

amidi -l          # Lists MIDI devices – "ADI-2 DAC" should appear
aplay -l          # Lists audio devices
lsusb             # Check USB devices

Check USB cable (some cables are charge-only)
Try a different USB port
Power-cycle the DAC

MQTT connection fails

journalctl -u rme-mqtt-bridge -e
# Look for: "MQTT connected rc=..." or error messages

Verify broker address and port (MQTT_HOST, MQTT_PORT)
Check credentials: /etc/default/rme-mqtt-bridge
Firewall: port 1883 must be open from Pi to broker
Test: mosquitto_sub -h BROKER_IP -u USER -P PASS -t 'rme/#'

Service won't start

systemctl status rme-mqtt-bridge
journalctl -u rme-mqtt-bridge --no-pager -n 30

Python error? → Run python3 /usr/local/bin/rme_mqtt_bridge.py manually
Missing EnvironmentFile? → See Installation

Debug mode

# Set DEBUG=1 via systemd override:
sudo systemctl edit rme-mqtt-bridge
# [Service]
# Environment=DEBUG=1

sudo systemctl restart rme-mqtt-bridge
journalctl -fu rme-mqtt-bridge

Wrong MIDI port

amidi -l
# Example output:
# Dir Device    Name
# IO  hw:1,0,0  RME ADI-2 DAC MIDI 1

If the port is not hw:1,0,0, adjust the service file:

# In /etc/systemd/system/rme-mqtt-bridge.service:
Environment=MIDI_PORT=hw:2,0,0   # Match your actual port

Acknowledgements

This project is largely built with the help of AI (Claude by Anthropic).

It relies on the following open-source projects:

Eclipse Paho MQTT – MQTT client library for Python
ALSA – amidi for USB-MIDI communication
Mosquitto – lightweight MQTT broker
raspotify – Spotify Connect client for Raspberry Pi
Home Assistant – open-source home automation platform

Thanks to all contributors and maintainers of these projects.

License

MIT License – Use at your own risk. Volume limits are intentionally conservative.

All product and company names are trademarks or registered trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

Navigation Menu

Repository navigation

About

Repository files navigation

Home Assistant MQTT Bridge for RME ADI-2 DAC

Quick Start

Highlights

Hardware

Audio Source Setup

Why SPDIF is enough

Signal Flow

Files

Prerequisites

Installation

Automatic (recommended)

Manual

Optional: Raspotify (Spotify Connect)

DietPi Notes

MQTT Topics

Home Assistant Example

Configuration

Troubleshooting

DAC not detected

MQTT connection fails

Service won't start

Debug mode

Wrong MIDI port

Acknowledgements

License

About

Releases

Packages

Contributors

Languages

Name		Name	Last commit message	Last commit date
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
conf		conf
env.example		env.example
install.sh		install.sh
raspotify-manager.service		raspotify-manager.service
raspotify_manager.py		raspotify_manager.py
requirements.txt		requirements.txt
rme-mqtt-bridge.service		rme-mqtt-bridge.service
rme_mqtt_bridge.py		rme_mqtt_bridge.py

Latest commit

History

Folders and files

Repository files navigation

Home Assistant MQTT Bridge for RME ADI-2 DAC

Quick Start

Highlights

Hardware

Audio Source Setup

Why SPDIF is enough

Signal Flow

Files

Prerequisites

Installation

Automatic (recommended)

Manual

Optional: Raspotify (Spotify Connect)

DietPi Notes

MQTT Topics

Home Assistant Example

Configuration

Troubleshooting

DAC not detected

MQTT connection fails

Service won't start

Debug mode

Wrong MIDI port

Acknowledgements

License

About

Topics

Resources

Stars

Watchers

Forks

Releases

Packages

Contributors

Languages