Raspberry Pi 4, ROT: KNX interface status unknown but knx connection is working

  • Platform information:
    • Hardware: _Raspberry Pi 4 2GB with Busware ROT KNX/1Wire via tpuarts:/dev/ttyAMA0

    • OS: Openhabian with openHAB 2.5.4-1

Hey guys I’m trying to integrate the KNX interface in Openhab. Every time when I add the Interface “KNX FT1.2 Interface” the status is “UNKNOWN” or “OFFLINE - COMMUNICATION_ERROR”.
Knxd is running and the ROT extension is working, because I can listen and see on the bus via

knxtool groupsocketlisten ip:localhost

knxd service

● knxd.service - KNX Daemon
Loaded: loaded (/lib/systemd/system/knxd.service; enabled; vendor preset: enabled)
Active: active (running) since Sun 2020-05-17 10:58:31 CEST; 5h 38min ago
Process: 492 ExecStart=/usr/local/bin/knxd -p /run/knxd/knxd.pid $KNXD_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 500 (knxd)
Tasks: 1 (limit: 4154)
Memory: 2.9M
CGroup: /system.slice/knxd.service
└─500 /usr/local/bin/knxd -p /run/knxd/knxd.pid --eibaddr=1.1.128 --client-addrs=1.1.129:8 -d -D -T -R -S -i --listen-local=/tmp/knx -b tpuarts:/dev/ttyAMA0

May 17 10:58:31 openhab systemd[1]: Starting KNX Daemon…
May 17 10:58:31 openhab systemd[1]: knxd.service: Can’t open PID file /run/knxd/knxd.pid (yet?) after start: No such file or directory
May 17 10:58:31 openhab systemd[1]: Started KNX Daemon.

I followed the knxd Raspi 4 readme but on my RPI 4 there is no ttyACM0 interface, just trough the /ttyAMA0.

Interface config:

Bridge knx:serial:bridge [


ACTION==“add”, SUBSYSTEM==“tty”, ATTRS{id}==“00241011”, KERNELS==“fe201000.serial”, SYMLINK+=“knx1”, OWNER=“knxd”


KNXD_OPTIONS="–eibaddr=1.1.128 --client-addrs=1.1.129:8 -d -D -T -R -S -i --listen-local=/tmp/knx -b tpuarts:/dev/knx1"



Unfortuanelly it also doesn’t change anything if I select everywhere the /ttyAMA0 instead of the /knx1 interface,

Either use knxd and the ip Bridge (with ROUTER or TUNNEL mode to localhost) or the serial Bridge.

Sometime the solutions are so easy :partying_face: Yes, just chooses Ip bridge and changing the ip to localhost solved the problem.

Thank you