It appears the Dymo 400 Twin Turbo does not report the correct device serial number. This prevents us from using more than one of these devices on a system because the device URI is not properly formed.

This will possibly need a USB device quirk added to the Linux kernel.

An alternative is to possibly implement a fix in dymo-cups-drivers. However, I think the problem occurs higher up the software stack.

How to identify the problem

1. Load wireshark and start recording packets from the master USB bus (bus:0) just prior to connecting the printer
2. Connect a Dymo 400 Twin Turbo printer to the system with USB
3. Stop logging USB packets after a minute
4. Review packet data and notice a packet received from the device has a malformed string

• The packet will be a GET DESCRIPTOR Response STRING with bLength: 30, bDescriptorType: 0x03 (String), and malformed bString: [malformed]

5. In terminal, lsusb -v -d 0922:0018
6. Notice the gibberish value in the iSerial field.
7. When setting up the printer, notice the device URI is usb://DYMO/LabelWriter%20Twin%20Turbo?serial=??????????????

The problem occurs because the default format for USB device descriptor STRINGs is uint-16-le. However, the Dymo-TT includes an extra byte at the start of the data returned from the device.

For example, the serial bString from a Dymo 450 is received as b'\x31\x00\x37\x00\x31\x00\x30\x00\x30\x00\x36\x00\x31\x00\x36\x00\x31\x00\x38\x00\x34\x00\x32\x00\x33\x00\x30\x00'. However, an example from the Dymo-TT is b'\x30\x30\x00\x36\x00\x31\x00\x30\x00\x33\x00\x30\x00\x31\x00\x30\x00\x31\x00\x36\x00\x31\x00\x35\x00\x37\x00\x35'.

Decoding the Dymo 450 string using uint-16-le yields "17100616184230", whereas the Dymo-TT string yields b''

# from pyUSB
import usb.core
import usb.util

vid = 0x0922       # Dymo VID
pid450 = 0x0020    # Dymo 450 PID
pidtt = 0x0018     # Dymo Twin Turbo PID

dymo450 = usb.core.find(idVendor=vid, idProduct=pid450)
dymott = usb.core.find(idVendor=vid, idProduct=pidtt)

print(f"Dymo 450 Serial: {dymo450.serial_number}")        # yields 17100616184230
print(f"Dymo-Twin-Turbo Serial: {dymott.serial_number}")  # yields gibberish
print(f"Dymo 450 Raw Serial value: {usb.control.get_descriptor(dymo450,254,0x03,dymo450.iSerialNumber,dymo450.langids[0])[2:30].tobytes().decode('utf-16-le')}")   # returns 17100616184230
print(f"Dymo-TT Raw Serial value: {usb.control.get_descriptor(dymott,254,0x03,dymott.iSerialNumber,dymott.langids[0])[2:30].tobytes().decode('utf-16-le')}")   # returns gibberish
print(f"Dymo 450 string result as bytes: {usb.control.get_descriptor(dymo450,254,0x03,dymo450.iSerialNumber,dymo450.langids[0])[2:30].tobytes().decode('utf-16-le').encode('utf-8')}")  # returns b'17100616184230'
print(f"Dymo 450 string result as bytes: {usb.control.get_descriptor(dymott,254,0x03,dymott.iSerialNumber,dymott.langids[0])[2:30].tobytes().decode('utf-16-le').encode('utf-8')}")  # returns b'\xe3\x80\xb0\xe3\x98\x80\xe3\x84\x80\xe3\x80\x80\xe3\x8c\x80\xe3\x80\x80\xe3\x84\x80\xe3\x80\x80\xe3\x84\x80\xe3\x98\x80\xe3\x84\x80\xe3\x94\x80\xe3\x9c\x80\xe3\x94\x80'

References

https://www.beyondlogic.org/usbnutshell/usb5.shtml#StringDescriptors