[RickPJ]

More information ...

Via the NetworkManager developers mailing list, I've been in contact with one of the lead NM developers, and there are definite problems in the way these ZTE devices interact.

NM 0.7.1 (as in Jaunty, not sure about Karmic) probes any serial ports on the device using AT commands to find which is a modem. It tries to avoid choosing two ports on the same parent device, but it's slightly out of sync with the latest version of HAL so it's not working properly. This is why you often get two devices listed.

You can fix this by adding a .fdi file that restores the previous HAL behaviour, but the problem is that it's then random whether it chooses ttyUSB1 or ttyUSB2. They both appear to behave as modems, but only ttyUSB2 will actually make a connection, ttyUSB1 will just hang. (Strictly speaking these are USB interfaces 1 and 3, which normally get assigned to ttyUSB 1 & 2.)

I've found that it's best to let it possibly detect two devices, then work our which is the correct one to use (see my scripts below).

The NM people now understand the problem and are trying to produce a solution that isn't a horrible hack.

However, there are still other issues that result in erratic behaviour. Sometimes you can plug the device in and it will connect immediately, other times you'll be fighting it for ages.

The issues are the serial port modes (which I think is a bug in the "option" driver, I'm trying to work that one out), and the continuous +ZUSIMR:2 messages that the modem spits out - these can be stopped by sending an initialisation command to the modem.

See my earlier post #35, with scripts attached that work round these problems. They're not pretty, they run in a terminal window, but for now they do the job!

Cheers, Rick