Ever since I moved to Ubuntu I haven’t been able to get my XDA II mini to stay connected. The output from dmesg was always the same:

[17179652.184000] usb 2-2: new full speed USB device using uhci_hcd and address 2
[17179652.356000] usb 2-2: configuration #1 chosen from 1 choice
[17179652.460000] usbcore: registered new driver usbserial
[17179652.464000] drivers/usb/serial/usb-serial.c: USB Serial support registered for generic
[17179652.464000] usbcore: registered new driver usbserial_generic
[17179652.464000] drivers/usb/serial/usb-serial.c: USB Serial Driver core
[17179652.472000] drivers/usb/serial/usb-serial.c: USB Serial support registered for PocketPC PDA
[17179652.472000] drivers/usb/serial/ipaq.c: USB PocketPC PDA driver v0.5
[17179652.472000] ipaq 2-2:1.0: PocketPC PDA converter detected
[17179652.472000] usb 2-2: PocketPC PDA converter now attached to ttyUSB0
[17179652.472000] usbcore: registered new driver ipaq

followed about 5 seconds later by:

[17179667.064000] usb 2-2: USB disconnect, address 2
[17179667.064000] ipaq ttyUSB0: PocketPC PDA converter now disconnected from ttyUSB0
[17179667.068000] ipaq 2-2:1.0: device disconnected

The solution turns out to be really simple – TURN YOUR PHONE ON!!

With the phone turned off Linux will detect the phone and set everything up then report the phone as disconnected about 5 seconds later. The solution is to turn your phone on. It doesn’t seem to matter if you turn it on before or after you connect it, just as long as you do it before running synce-serial-start.