do you have multiple USB devices attached to your system (apart from HDDs etc)? If so, try with only the USB-interface connected to the host and try again. Other than that, no idea, google might be your friend (knxd issues with MDT …).
Once the USB connectoin issue is resolved, you can point xknx to the local IP if your HA host
How can I point it to the local IP of my HA host?
I am confused since the configuration page says that I don’t have to enter an IP address?
Is this done all magically with the port configuration at the bottom of the config page?
Maybe you can provide me some screenshots of how the config should look like please 
No, the USB-Interface is the only thing that is connected to the USB ports.
I can’t tell you how the config for your particular USB device has to look like - some USB devices seem to require certain “usb_filters”, others don’t. You will have to search the web if the MDT one requires certain filters or not (or try some filters, see knxd documentation for possible filters and what they do).
But in general, the default config of the add-on should work for most USB KNX-interfaces from what I have read. So Interface driver set to USB and the filter to single. The setting Interface IP-Address is ONLY needed for the drivers mentioned in description of this setting, no others (so for UART interfaces over IP). So for a USB KNX interface you do NOT have to configure anything IP related in the knxd add-on. I was talking about the HA component. You can try to use IP auto-detection (as described in the settings of the HA component) or enter the IP of the device you run the add-on on. I doubt that 127.0.0.1 would work since knxd is running in a container and not directly on localhost, so you would probably need the internal IP of the container within the docker VLAN, or just use your “external” local IP.
But this won’t help you if you do not first fix the USB connection issue. Since I do not have any USB KNX interfaces, I can neither test nor debug things. If you can’t get knxd to run, you can also try the Calimero add-on which farmio linked a couple posts earlier. KNXD add-on: covert your KNX-USB interface into an IP interface that can be used by HA - #189 by farmio
don’t they run with net=host?
there appears to be a new version of knxd available since 16 days, but it appears to be missing other changes that had been merged to the main branch of knxd, which might fix some USB issues from what I have seen. I created a ticket over at knxd and asked if this was intentional. Once I got feedback from them, I’ll create a new version of the add-on with the latest knxd version, which might or might not fix your USB issue.
ah yes, it does run on host network. So 127.0.0.1 could work, never tried and just assumed it didn’t. I’m a container noob.
I assume you mean knxd 
so it finally happened. I was so careful in the other reply to not mix them up 
Yes, ofc knxd.
@sla89 new version of the add-on is available. Please check if the new knxd version fixes your USB connection issue.
thank you so much for your support!
i will give it a try but I dont have time until next week
I will give you my update asap!
No… for me dont work. I have TPUART busware , version 0.4.4 is ok,
Nonfunctional 0.4.5 and also 0.4.6. is not ok.
yeah, I noticed that something it broken in the images, but I can’t figure out what. If I compile the same add-on locally on my RPI, it’s starting up fine. But the image compiled via github actions has startup issues (something about permissions). Still investigating. It’s best to not update for now and stick to 0.4.4
startup issues should finally be resolved in 0.4.7 now. Sorry for the inconvenience with the broken update.
Hi da-anda,
I am still at 0.4.2 as there are problems starting up since each update after 0.4.2. It seems there is no image on github.
I have HA running in a linux virtual machine in unraid and the error message says:
‘Image Package hass-io-addons-amd64-addon-knxd · GitHub does not exist for addon_ecaeb50e_knxd’
In my humble opinion it could have to do sth. with the point you already mentioned: The “SHA of the GIT repo”… Hope this helps - if you need more info, please let me know!
images are there. 0.4.2 was the last version without precompiled images. If every version after that fails for you to install, I suspect that something maybe is blocking the access to the Github container repo. The amd64 version of 0.4.7 has been downloaded 7 times so far, so it must be working for others.
edit:
my suggestion would be:
Hi @da-anda
thank you for the new release and for your effort.
I stayed on 0.4.3 for months as newer releases didn’t work for me (mainly cause ETS connections were unstable at best)
Just wanted to let you know that 0.4.7 works like a charm for me (using the HA integration to connect to the bus as well as ETS) 
You made not my day, but at least half my year 
That did the trick!!
I did not try to uninstall and reinstall it - but now everything works like a charm.
Thanks for your answer and the whole add-on!
About my libusb error:
The knxd docs say about usb devices that “You may need a UDEV rule that changes the USB device’s ownership to knxd.”.
I am running hassos on my rpi 4 and there this is not possible.
After updating to the latest version of your addon I will also follow this instructions (No UDEV Rules?) and try ttyUSB0 or ttyUSB1 (I hope they are available…).
Is anybody running this add on within hassos directly?
Not that I know anything about knxd, but Addons in general only run on HA OS (and supervised). That’s what they are made for.
Oh sorry, my bad, I don’t know that Thank you for the clarification.