cmqttd allows you to expose a C-Bus network to an MQTT broker. This daemon replaces cdbusd (which required D-Bus) as the abstraction mechanism for all other components.

It uses Home Assistant style MQTT-JSON Light components, and supports MQTT discovery. It should also work with other software that supports MQTT.

It can also be run inside a Docker container.

This replaces sage (our custom web interface which replaced Wiser).

cmqttd with Home Assistant has many advantages over Wiser:

  • No dependency on Flash Player or a mobile app
  • No requirement for an Ethernet-based PCI (serial or USB are sufficient)
  • Touch-friendly UI based on Material components
  • Integrates with other Home Assistant supported devices
  • No hard coded back-doors or outdated software from 2006

See also: Instructions for Wiser users.


Only the default lighting application is supported by cmqttd. Patches welcome!


cmqttd requires a MQTT Broker (server) to act as a message bus.


For these examples, we’ll assume your MQTT Broker:

  • is accessible via on the default port (1883).
  • does not use transport security (TLS)
  • does not require authentication

This setup is not secure; but securing your MQTT Broker is out of the scope of this document.

For more information, see MQTT options.

To connect to a serial or USB PCI connected on /dev/ttyUSB0, run:

$ cmqttd --broker-address --broker-disable-tls --serial /dev/ttyUSB0

To connect to a CNI (or PCI over TCP) listening at, run:

$ cmqttd --broker-address --broker-disable-tls --tcp

If you’re using Docker, the container also needs a route to the CNI’s IP address.


If you haven’t installed the library, you can run from a git clone of libcbus source repository with:

$ python3 -m cbus.daemons.cmqttd -b [...]

For Wiser users

This software is not compatible with Wiser Home Control (Clipsal’s web interface for C-Bus). Wiser and cmqttd both take full control the CNI, and will interfere with one another.

Additionally, using both on the same C-Bus network (with different PCI/CNIs) may cause issues, as both presume they are the sole source of network services such as time synchronisation.

Wiser Home Control Mk1 (5200PG)

The Wiser Home Control Mk1 has an external CNI which should be usable with cmqttd.

  1. Switch off and completely disconnect the Wiser.

  2. Disconnect the “busbar” between the Wiser and the CNI.

  3. Connect the CNI to power and network directly.

    You may need to use Toolkit to configure the CNI with an IP address which can be accessed from the host you’re running cmqttd on. The default IP address for the CNI is

  4. Continue setting up cmqttd.

  5. Once you’ve verified cmqttd is working correctly, responsibly dispose of the Wiser 1 at your nearest e-waste facility.


The Wiser 1 has very outdated and insecure software (from 2006). You should not use it under any circumstances, or for any purpose.

Wiser Home Control Mk2 (5200WHC2)

The Wiser Home Control Mk2 has an internal CNI which cannot be used, because the Wiser’s software conflicts with cmqttd.

You will need to get a real, standalone PCI or CNI.


The author of this software does not have access to any Wiser hardware anymore, and the Wiser 2’s list price of 2000 AUD is far beyond the budget for this project.

Hint hint, Schneider Electric… we should talk :)


cmqttd has many command-line configuration options.

A complete list can be found by running cmqttd --help.

C-Bus PCI options

One of these must be specified:

--serial DEVICE

Serial device that the PCI is connected to, eg: /dev/ttyUSB0.

USB PCIs (5500PCU) act as a SiLabs cp210x USB-Serial adapter, its serial device must be specified here.


IP address and TCP port where the PCI or CNI is located, eg:

Both the address and the port are required. CNIs listen on port 10001 by default.

See also: Instructions for Wiser users.

MQTT options

--broker-address ADDR

Address of the MQTT broker. This option is required.

--broker-port PORT

Port of the MQTT broker.

By default, this is 8883 if TLS is enabled, otherwise 1883.


Disables all transport security (TLS). This option is insecure!

By default, transport security is enabled.

--broker-auth FILE

File containing the username and password to authenticate to the MQTT broker with.

This is a plain text file with two lines: the username, followed by the password.

If not specified, password authentication will not be used.

--broker-ca DIRECTORY

Path to a directory of CA certificates to trust, used for validating certificates presented in the TLS handshake.

If not specified, the default (Python) CA store is used instead.

--broker-client-cert PEM
--broker-client-key PEM

Path to a PEM-encoded client (public) certificate and (private) key for TLS authentication.

If not specified, certificate-based client authentication will not be used.

If the file is encrypted, Python will prompt for the password at the command-line.


--project-file CBZ

Path to a C-Bus Toolkit project backup file (CBZ) to use for labelling group addresses.

This doesn’t affect the entity paths or unique IDs published in MQTT.

Only single-network projects using the lighting application are supported. DLT labels are not supported.

For group addresses with unknown names, or if no project file is supplied, generated names like C-Bus Light 001 will be used instead.


If you don’t have a project file backup from your installer, you can always rename entities from within Home Assistant itself.

This labels are not stored on C-Bus units, so Toolkit cannot download this information from the network.

Time synchronisation

By default, cmqttd will periodically provide a time signal to the C-Bus network, and respond to all time requests.

Local time is always used for time synchronisation. You can specify a different timezone with the TZ environment variable.

C-Bus’ time implementation has many limitations:

  • C-Bus date values and time values are two separate network variables – there is no analog to Python’s datetime.datetime type. This can trigger race conditions around midnight if the messages are not handled atomically by receivers.

    cmqttd will always send the date and time as a single message, in an attempt to mitigate this issue.

  • C-Bus time values have an optional “daylight saving time” flag, with three states: “no daylight saving offset applied”, “time advanced by 1 hour for daylight saving”, and “unknown”.

    Because this is cannot be used to present daylight saving time properly (eg: Lord Howe Island turns their clocks forward 30 minutes for DST), and there are far too many edge cases with time zone handling, cmqttd will always report “unknown”, in an attempt to make sure C-Bus units do not attempt any time conversions.

  • C-Bus does not support leap seconds. You can mitigate this by synchronising your clock using an NTP server with leap second smearing.

To schedule scenes in C-Bus, you should use something like Home Assistant, rather than embedded controllers directly attached to the C-Bus network.

--timesync SECONDS

Periodically sends an unsolicited time signal to the C-Bus network.

By default, this is every 300 seconds (5 minutes).

If set to 0, cmqttd will not send unsolicited time signals to the C-Bus network.


Disables responding to time requests from the C-Bus network.


--log-file FILE

Where to write the log file. If not specified, logs are written to stdout.

--verbosity LEVEL

Verbosity of logging to emit. If not specified, defaults to INFO.


Using with Home Assistant

cmqttd supports Home Assistant’s MQTT discovery protocol.

To use it, just add a MQTT integration using the same MQTT Broker as cmqttd with discovery enabled (this is disabled by default). See Home Assistant’s documentation for more information and example configurations.

Once the integration and cmqttd are running, each group addresses (regardless of whether it is in use) will automatically appear in Home Assistant’s UI as two components:

  • lights: light.cbus_{{GROUP_ADDRESS}} (eg: GA 1 = light.cbus_1)

    This implements read / write access to lighting controls on the default lighting application. “Lighting Ramp” commands can be sent via the standard brightness and transition extensions.

    By default, these will have names like C-Bus Light 001.

  • binary sensors: binary_sensor.cbus_{{GROUP_ADDRESS}} (eg: GA 1 = binary_sensor.cbus_1).

    This is a binary, read-only interface for all group addresses.

    An example use case is a PIR (occupancy/motion) sensor that has been configured (in C-Bus Toolkit) to actuate two group addresses – one for the light in the room (shared with an ordinary wall switch), and which only reports recent movement.

    cmqttd doesn’t assign any class to this component, so this can be used however you like. Any brightness value is ignored.

    By default, these will have names like C-Bus Light 001 (as binary sensor).

All elements can be renamed and customized from within Home Assistant.

Running in Docker

This repository includes a Dockerfile, which uses a minimal Alpine Linux image as a base, and contains the bare minimum needed to make cmqttd work.

On a system with Docker installed, clone the libcbus git repository and then run:

# docker build -t cmqttd .

This will download about 120 MiB of dependencies, and result in about 100 MiB image (named cmqttd).

The image’s startup script ( uses the following environment variables:


The timezone to use when sending a time signal to the C-Bus network.

This must be a tz database timezone name (eg: Australia/Adelaide). The default (and fall-back) timezone is UTC.


The serial port that the PCI is connected to. USB PCIs appear as a serial device (/dev/ttyUSB0).

Docker also requires the --device option so that it is forwarded into the container.

This is equivalent to cmqttd --serial. Either this or CNI_ADDR is required.


A TCP host:port where a CNI is located.

This is equivalent to cmqttd --tcp. Either this or SERIAL_PORT is required.

See also: Instructions for Wiser users.


IP address where the MQTT Broker is running.

This is equivalent to cmqttd --broker-address. This environment variable is required.


Port address where the MQTT Broker is running.

This is equivalent to cmqttd --broker-port.


If set to 1 (default), this enables support for TLS.

If set to 0, TLS support will be disabled. This is equivalent to cmqttd --broker-disable-tls.


If set to 1 (default), cmqttd will respond to time requests from the C-Bus network.

If set to 0, cmqttd will ignore time requests from the C-Bus network. This is equivalent to cmqttd --no-clock.


Number of seconds to wait between sending an unsolicited time signal to the C-Bus network.

If set to 0, cmqttd will not send unsolicited time signals to the C-Bus network.

By default, this will be sent every 300 seconds (5 minutes).

This is equivalent to cmqttd --timesync.

The image is configured to read additional files from /etc/cmqttd, if present. Use Docker volume mounts to make the following files available:


Username and password to use to connect to an MQTT broker, separated by a newline character.

If this file is not present, then cmqttd will try to use the MQTT broker without authentication.

This is equivalent to cmqttd --broker-auth.


A directory of CA certificates to trust when connecting with TLS.

If this directory is not present, the default (Python) CA store will be used instead.

This is equivalent to cmqttd --broker-ca.

/etc/cmqttd/client.pem, /etc/cmqttd/client.key

Client certificate (pem) and private key (key) to use to connect to the MQTT broker.

This is equivalent to cmqttd --broker-client-cert and cmqttd --broker-client-key.


C-Bus Toolkit project backup file to use as a source for labelling group addresses.

This is is equivalent to cmqttd --project-file.


All file and directory names are case-sensitive, and must be lower case.

Docker usage examples

To use a PCI on /dev/ttyUSB0, with an unauthenticated and unencrypted MQTT Broker at, and the time zone set to Australia/Adelaide:

# docker run --device /dev/ttyUSB0 -e "SERIAL_PORT=/dev/ttyUSB0" \
    -e "MQTT_SERVER=" -e "MQTT_USE_TLS=0" \
    -e "TZ=Australia/Adelaide" cmqttd

To supply MQTT broker authentication details, create an /etc/cmqttd/auth file to be shared with the container as a Docker volume:

# mkdir -p /etc/cmqttd
# touch /etc/cmqttd/auth
# chmod 600 /etc/cmqttd/auth
# echo "my-username" >> /etc/cmqttd/auth
# echo "my-password" >> /etc/cmqttd/auth

Then to use these authentication details, with TLS enabled:

# docker run --device /dev/ttyUSB0 -e "SERIAL_PORT=/dev/ttyUSB0" \
    -e "MQTT_SERVER=" -e "TZ=Australia/Adelaide" \
    -v /etc/cmqttd:/etc/cmqttd cmqttd

If you want to run the cmqttd daemon in the background, on the same device as a Home Assistant server with the MQTT broker add-on:

# docker run -dit --name cbus --restart=always \
    --device /dev/ttyUSB0 --network hassio \
    -e "TZ=Australia/Adelaide" -e "BROKER_USE_TLS=0" \
    -e "SERIAL_PORT=/dev/ttyUSB0" \
    -e "MQTT_SERVER=core-mosquitto" \


You can verify the hostname of hassio’s MQTT broker with: # docker inspect addon_core_mosquitto

If you want to run the daemon manually with other settings, you can run cmqttd manually within the container (ie: skipping the start-up script) with:

# docker run -e "TZ=Australia/Adelaide" cmqttd cmqttd --help


When running without the start-up script:

  • you must write cmqttd twice: first as the name of the image, and second as the program inside the image to run.
  • none of the environment variables (except TZ) are supported – you must use cmqttd command-line options instead.
  • files in /etc/cmqttd are not used unless equivalent cmqttd command-line options are manually specified.