I have a HUAWEI E182 USB HSPA+ Modem, which works wonders on my Linux laptop, and I am attempting to get it working on the SheevaPlug. The Plug's kernel detects it fine, however when I enter in my PIN using comgt, the light flashes blue for just a split second confirming registration on the network then goes back to green.
Since I am connecting to the plug using cu, I can see the various kernel output, like it being inserted and detected. The output is no different than from my laptop. comgt detects the device with no problems, but then constantly waits for network registration.
I am guessing that it draws additional power from USB when turning on the cellular radio, so when it cannot draw more power, the 3G chip just turns itself back off. This is very unfortunate, as an external power source is needed in order for the plug to connect to a 3G network to provide remote data.
Keep this in mind when developing remote applications which may just use solar energy for example, you may need to also supply the 3G modem with it's own power source.
Does WiFi act the same way? When WiFi powers up it's radio, does it also draw more power, and which USB WiFi dongles would work best?