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knxd Build Status

KNX is a very common building automation protocol which runs on dedicated 9600-baud wire as well as IP multicast. knxd is an advanced router/gateway which runs on any Linux computer; it can talk to all known KNX interfaces.

STOP if you install on Debian

Debian packaging has been moved to the debian branch. Please use that branch (by way of git checkout debian) if you're following some (outdated …) installation instructions for Debian, Ubuntu or their derivatives.

Stable version

This version should be OK for general use.

Check the Wiki page for other version(s) to use.

Known bugs

  • ETS programming may or may not work out of the box. You might need to use the single filter in front of your KNX interface.


Daemon Configuration

Daemon configuration differs depending on whether you use systemd. If "systemctl status" emits something reasonable, you are.

If you use Linux and systemd, the configuration file is /etc/knxd.conf. Socket activation is used for the default IP and Unix sockets (port 6720 and /run/knx, respectively). If not, the location of your configuration file depends on your init system.

In knxd or knxd.conf, KNXD_OPTS can be set to either the legacy command line arguments, or the location of the new .ini (e.g. KNXD_OPTS=/etc/knxd.ini)

New ".ini" configuration file

knxd is typically started with "knxd /etc/knxd.ini".

The file format is documented in "doc/inifile.rst". You might want to use the program "/usr/lib/knxd_args" to create it from previous versions' command-line arguments.

Backward Compatibility

The default Unix socket is /run/knx. Old eibd clients may still use /tmp/eib to talk to knxd. You need to either change their configuration, or add "-u /tmp/eib" to knxd's options. (This was the default for "-u" before version 0.11.)

New Features since 0.12

see for earlier changes

  • 0.14.41

    • speed up CGI initial setup (a lot)
    • support another USB interface
    • found another uninitialized variable
  • 0.14.39

    • Fixed two problems with the "pace" filter that resulted in excessive delays.
  • 0.14.38

    • knxd's udev rules were lost in the Debian branch. Restored (to systemd subdir).
  • 0.14.37

    • Fix a memory leak in the FT12 driver
    • fix the console rule in README
  • 0.14.35

    • Fixes for FreeBSD
  • 0.14.34

    • Cleanup: remove debian packaging, will be in a separate branch
  • 0.14.33

    • There is a new "retry" filter which controls closing and re-opening a misbehaving driver. This filter is implicitly auto-inserted in front of a driver.

    • Internal: Driver errors are now signalled with "stopped(true)" instead of "errored" which reduces code duplication.

    • Default timeout for EMI acks increased to 2 seconds Some USB interfaces manage to be abysmally slow Also hopefully-fixed USB retry and shutdown handling so that the "retry" filter can do its work.

    • Replies from devices in programming mode are no longer retransmitted to the originating interface.

  • 0.14.32

    • Tags no longer use a leading 'v'.

    • udev rule for SATEL USB interface

  • 0.14

    • Code configuration

      • There are no longer separate --enable-tpuarts and --enable-tpuarttcp options. Instead, you control both with --enable-tpuart. (This is the default anyway.)
    • Configuration file

      • includes a translator (knxd_args) from options to config file

      • All settings are still usable via the command line

    • Complete stack refactored

      • You may now use global filters.

      • USB handling updated

      • Most device-specific drivers are now split into a top part which translates KNX packets to wire format (usually CEMI), and a bottom part which transmits/receives the actual data. This enables extensive code sharing; knxd also can use TCP connections instead of actual serial devices.

    • Startup sequencing fixed: KNX packets will not be routed until all interfaces are ready.

      Also, systemd will not be signalled until then.

      • Configuration options to not start, or start and ignore failures of, specific interfaces

      • knxd will now retry setting up an interface

    • use libfmt for sane and type-safe formatting of error and trace messages

    • packet-level "logging" calls in various drivers have been removed

      • logging packets is now done with the new "log" filter

      • Logging of complete packets (inconsistently bit 1, 2, or 8 of the tracing mask) has been removed

      This also applies to global packet logging.

    • Complain loudly (and early) if knxd needs -E / client-addrs=X.Y.Z:N

    • knxd can restart links when they fail, or start to come up.

    • Interfaces are now either used normally, or in bus monitor mode. This is set in the configuration file / on the command line. There is no longer a way to switch between these modes; "knxtool busmonitor" will no longer change the state of any interface.

    • Queuing and flow control

      Previously, all drivers implemented their own queueing for outgoing packets, resulting in duplicate code and hidden errors.

      In v0.14, the main queueing system will pace packets for the slowest device. If you don't want that, use the "queue" filter on the slow device(s).

      All queues in individual drivers have been removed.

    • EMI handling refactored

      This eliminated some common code, found a couple of bugs, and lets us use a common logging module (controlled by bit 0 of the tracing mask) for comprehensive packet debugging.


  • knxd was rewritten to use libev instead of pthsem.

  • knxd now supports multiple interfaces, back-ends, and KNX packet filters.


This code is a fork of eibd 0.0.5 (from bcusdk)

For a (german only) history and discussion why knxd emerged, please also see: eibd(war bcusdk) Fork -> knxd


When in doubt, please check out the branch corresponding to your Linux distribution's flavor, and read this section there.

This part covers "manual" installation.

# first, install build tools and dependencies. You need git, autotools, and gcc/g++.
#: check your Linux distribution's documentation if you don't know how
# You also need a "knxd" user.

# get the source code
git clone

# build+install knxd
cd knxd
git checkout main
./configure --help
./configure --your-chosen-options
make install
cd ..

# Now switch to the "knxd" user and start the daemon.

If you would like to submit patches for Mac OSX or Windows, go ahead and create a pull request, but please be prepared to maintain your code.

Adding a TPUART USB interface

If you attach a (properly programmed) TUL ( to your computer, it'll show up as /dev/ttyACM0. This is a problem because (a) it's owned by root, thus knxd can't access it, and (b) if you ever add another serial interface that uses the same driver, knxd will use the wrong device.

Therefore, you do this:

  • Run udevadm info --attribute-walk /sys/bus/usb/drivers/cdc_acm/*/tty/ttyACM0.

    We're interested in the third block. It contains a line ATTRS{manufacturer}=="". Note the KERNELS=="something" line (your something will be different).

  • Copy the following line to /etc/udev/rules.d/70-knxd.rules:

    ACTION=="add", SUBSYSTEM=="tty", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="204b", KERNELS=="something", SYMLINK+="knx1", OWNER="knxd"

    Of course you need to replace the something with whatever udevadm displayed. An example file should be in /lib/udev/rules.d/.

  • Run udevadm test /sys/bus/usb/drivers/cdc_acm/*/tty/ttyACM0.

  • verify that /dev/knx1 exists and belongs to "knxd":

    ls -lL /dev/knx1

  • add -b tpuarts:/dev/knx1 to the options in /etc/knxd.conf.

If you have a second TPUART, repeat with "ttyACM1" and "knx2".

You'll have to update your rule if you ever plug your TPUART into a different USB port. This is intentional.

Adding any other USB interface

These interfaces should be covered by the udev file knxd installs in /lib/udev/rules.d. Simply use -b usb: to talk to it, assuming you don't have more than one.

Adding a TPUART serial interface to the Raspberry Pi

On the Raspberry Pi 2 and 3 the console is /dev/ttyAMA0. The udev line is:

ACTION=="add", SUBSYSTEM=="tty", KERNELS=="ttyAMA0", SYMLINK+="knx1", OWNER="knxd"

On the Raspberry Pi 4 the console is on /dev/ttyACM0. The udev line is:

ACTION=="add", SUBSYSTEM=="tty", KERNELS=="ttyACM0", SYMLINK+="knx1", OWNER="knxd"

This rule creates a symlink /dev/knx1 which points to the console. The knxd configuration will use that symlink.

On the Raspberry Pi 2 and 3 you need to disable the serial console. Edit /boot/cmdline.txt and remove the console=ttyAMA0 entry. Then reboot.

On the Raspberry Pi 3, the serial console is on ttyAMA1 by default. However, that is a software-driven serial port – the single hardware serial interface is used for Bluetooth on the Pi3. Varying CPU speed causes this port to be somewhat unreliable. If this happens, disable Bluetooth by adding


to /boot/config.txt, run systemctl disable hciuart, and reboot. The TPUART module is now back on ttyAMA0.

Migrating to 0.14

  • If you build knxd yourself: install the libfmt-dev package, if possible.

    The knxd build process will try to download and build libfmt when that package is not present.

  • knxd is now configured with a .ini-style configuration file.

    The old way of configuring knxd via a heap of position-dependent arguments is still supported.

    You can use /usr/lib/knxd_args <args-to-knxd> to emit a .ini file that corresponds to your old list of arguments.

  • Not configuring client addresses is now a hard error. Knxd will no longer multiplex its clients onto its own address.

  • knxd will not start routing any packets unless startup is successful on all interfaces.

    This means that it is now safe to use "socket activation" mode with systemd. Previously, knxd might have lost the initial packets.

  • knxd can now attach filters to a single interface, or to the core (i.e. all packets get filtered).

  • Tracing no longer logs the actual decoded contents of packet. If you need that, use a "log" filter appropriately.

  • knxd now transmits data synchronously, i.e. individual drivers no longer buffer data for transmission. If you don't want that, use the "queue" filter on slow interfaces.

Migrating to 0.12

  • If you build knxd yourself: install the libev-dev package. You no longer need the pthsem packages.

  • You may need "-B single" in front of any "-b ipt:" or "-b usb:", esp. when you need to program a device; normal use is often not affected. knxd emits a warning

    Message without destination. Use the single-node filter ('-B single')?

    when it detects mis-addressed packets.

  • You need "-e"; knxd no longer defaults to address 0.0.1.

  • You need "-E" if you want to allow clients to connect (options -u -i -T). As that's almost always the case, knxd will print a warning if this option is missing.

  • If you use knxtool's management tools (any command with "progmode" or whose name starts with 'm'), please open an issue because knxd currently does not support these commands.

Migrating from eibd

  • Before you build knxd: remove any traces of the old eibd installation from /usr/local, or wherever you installed it.

  • The order of arguments is now significant. Among the "-D -T -R -S" arguments, -S must occur last. Arguments which modify the behavior of an interface must be in front of that interface. Global arguments (e.g. tracing the datagram router) must be in front of the "-e" option.

  • The 'groupswrite' etc. aliases are no longer installed by default. To workaround, you can either add /usr/lib/knxd to your $PATH, or use knxtool groupswrite.

  • If you use Debian Jessie or another systemd-based distribution, /lib/systemd/system/knxd.socket is used to open the "standard" sockets on which knxd listens to clients. You no longer need your old -i or -u options.

  • knxd's Unix socket should never have been located in /tmp; the default is now /run/knx. You can add a "-u /tmp/eib" (or whatever) option if necessary, but it's better to fix the clients.


  • Any contribution is very welcome
  • Please use Github and create a pull request with your patches
  • Please see SubmittingPatches to correctly Sign-Off your code and add yourself to AUTHORS (tools/list_AUTHORS > AUTHORS)
  • Adhere to our coding conventions. The git archive includes a helpful .vimrc file if you use VIM.

Compensation – personal statement

KNX development is not a simple matter and requires both time and dedicated hardware for tests. The ETS software isn't exactly cheap, either, and there is no free replacement. (I'd like to change that.)

Thus, wearing my hat as the (current) main author, I (Matthias Urlichs) would like to ask you to consider contributing to knxd's development.

  • paypal:
  • bitcoin: 1G2NKavCVt2adxEUZVG437J2tHvM931aYd
  • SEPA: DE25760400610535260401 @ COBADEFFXXX

I can issue a commercial invoice if required.

If you'd rather gift some hardware, please ask.