Re: Looking for advice about using NM with a Sprint U301 modem

[Dan Williams <dcbw redhat com>]

On Thu, 2010-05-27 at 12:04 -0400, Daenyth Blank wrote:
> Hi all,
> 
> I'm trying to find out some information regarding the Sprint U301 3G
> modem. Our use case for it is that it will be attached to an embedded
> machine running ubuntu with networkmanager, in addition to our
> software. I've been trying to get this modem to connect reliably and
> am having some issues with it. I've added a udev rule so that the
> usbserial driver is given the correct vendor/product information, and
> it connects automatically on boot, but not reliably. Some boots it
> does not connect at all and won't until I reboot. Sometimes it
> disconnects while the machine is running. If it disconnects either by
> itself or from deactivating the connection, it will not connect again
> and needs a reboot. The nm/mm logs say that serial requests are timing
> out when it's in the non-connected state. I haven't been able to
> recover from the disconnected state with anything about a reboot.
> 
> Is there anything we can do with this device to increase reliability?
> Failing that, can you recommend a usb Sprint 3G modem that will be
> more reliable? If there are none, do you have any recommendations for
> any brand of 3G modem that will work well in this situation? The boxes
> will be deployed where manual access is not easy, so it needs to be
> able to connect and recover from disconnections automatically, or at
> least in a way that can be scripted easily.

You're certainly not going to be able to get the WiMAX part of the
device working automatically since we dont' have drivers for the Beceem
chipset of the WiMAX side.  However, the EVDO side should work with
cdc-acm, so if you have to use 'usb-serial' there's already something
wrong.

I suspect you need to use usb_modeswitch to eject the fake CD that the
device provides too, correct?

Honestly, UTStarcom-based devices (which the 300 and 301 are rebrands
of) often don't work that well as you've found out.  I'd recommend a
Sierra device instead, as Sierra is also very active in Linux kernel
development and has great support for their devices.

Dan