Now it’s almost automatically attached as modem after insertion and people have been contributing to list of device-and-target device after mode-switching (find it as /usr/share/usb_modeswitch/configPack.tar.gz). At least for Raspberry Pi (RPi), I have one device list from August 2012 when playing around with XBian 0.8.3 and one from May 2012 in when using Raspbian Wheezy (2012-08-16).

Huawei E220 requires no mode-switch from vendor-product ID 12d1:1003 to function as modem

There is still wrapper for udev in /lib/udev/rules.d/40-usb_modeswitch.rule and my Huawei E153 HSDPA stick recognized and switched successfully as shown:

usb_modeswitch: switching device 12d1:1446 on 001/005
...
logger: usb_modeswitch: switched to 12d1:14ac on 001/006

But I didn’t get there in the first place. Because of USB power problem (detailed in previous post), I used to plug USB devices before powering up so that I could use Y-cable injected by separate power source without powered USB-hub. It turned out that if I had plugged the USB before powering up the RPi the mode-switching didn’t occur.

The HSDPA USB modem used is Huawei E153 appearing in lsusb with vendor-product ID 12d1:1446. Using aforementioned XBian and target device 12d1:140c (suggested in Santinoli’s post), I arbitrarily succeeded to switch to modem and dial internet with pppd.

[root]$ usb_modeswitch -v 12d1 -p 1446 -P 140c

(I placed Santinoli’s config in /etc/usb_modeswitch.conf)
This wasn’t stable however (also note that XBian consumed CPU above 50% for xbmc).

Later I find out that it will automatically switch to 12d1:14ac instead when plugged in after RPi is up. However, since it also won’t switch if plugged before power-up, I also try to mode-switch manually using config file found inside /usr/share/usb_modeswitch/configPack.tar.gz archive named 12d1:1446.

[root]$ usb_modeswitch -v 12d1 -p 1446 -c 12d1\:1446

It doesn’t seem to work. Modification to something close to my previous config also fails. Hence, consistent result only occurs if the stick is plugged in after RPi up. Then I decide to use USB-hub (also detailed in previous post) to tackle power issue (it will reboot anyway if you plug in without adequate powering). However, after successful mode-switch what’s being reported in eLinux Wiki often happens: it slows down, try lsub command for example.

Currently I give up the idea of using that modem and choose older Huawei E220:

1. No usb_modeswitch. Driver attached directly by the kernel as option.ko device (this device has been on the list for long)
2. Stable. No slowing down

The E153 modem itself has been implemented to stream video using the higher ARM type BeagleBoard-xM without significant stability issue (check my YouTube demo). It mode-switched when powering up Ubuntu on the Beagle.

Y-cable for USB modem stick & various current rating-AC power adapters for smartphone/tablet to go with Raspberry Pi

eLinux Wiki lists market available USB-hubs reported to work. A decent brand (that will cost you) qualifies:

• Doesn’t leak power back to RPi via USB port (check this by unplugging the main power, then check the red LED indicator) as this will interfere with the reboot command (physical state vs software).
• Provides charging from one of its port for RPi, meaning no separate source for the exclusive 700 mA requirement. A single AC power adapter with high current rating will fit all (check single power connectivity sketch in this blog post)

An ugly situation when I plugged in WiFi stick and modem looks like:

kernel: [ 1836.871640] smsc95xx 1-1.1:1.0: eth0: Failed to read register index 0x00000118
...
kernel: [ 1803.780601] phy0 -> rt2x00usb_vendor_request: Error - Vendor Request 0x07 failed for offset 0x101c with error -110.

tail of the above syslog is saying error with the (1) ethernet (this is actually also a USB 2.0 but not appearing in lsusb command) and (2) the WiFi stick used (in this case with RT5370 chipset). Then, of course (3) doing things with the just plugged modem you’ll expect more instability.

I mentioned BeagleBoard-xM which also came with similar USB ethernet on-board. Unfortunately, Beagle was more stable when my case was to have it stream a zoom-camera input to internet (check my YouTube demo). The camera decoder and modem were both USB plugged without Y-cable or additional power supply. As a standalone system, part of the design was to reboot under trouble detected by the software. Again, OS command reboot is not achievable consistently with the RPi when power backfeeds through USB port.

(PS: Note that previous comparison solely points out what to expect when dealing with USB among other considerations e.g. price, different ARM, etc. which are entirely different.)

As an absolute requirement for me, I found a powered USB-hub available in Indonesian market as 7 ports XTec Go. Yes, it leaks power back as confirmed by the vendor-product ID 05e3:0608 of the chipset listed in eLinux Wiki lists with a bunch of different names (judging the picture, Hama is closest).

$ lsusb
...
Bus 001 Device 004: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
Bus 001 Device 005: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
...

Three Musketeers: powered USB-hub (Genesys chipset), Huawei E220 HSDPA modem, and TL-WN727N WiFi stick

My el cheapo USB-hub, HDSPA modem, and WiFi stick are the matchmaking of brands shown in the above image. It achieves long uptime like 6 hours serving internet when RPi used as router. I still use separate AC power adapter on the go with me: regular 700 mA that comes with smartphone will do for the RPi, while for the USB-hub, I have 2A rating from tablet charger. However, I’ve also plugged separate 500 mA charger for the hub without problem and/or excessive heat (you need to touch the supply sometime to feel any nasty heat as some of them might have been low quality build that could blow up. Yes it did). My plan with mobility is to have power bank with dual USB charging output (this Hame has 1A and 2.1A) when no AC source nears.

Have I tested other USB modem stick? Check my other post related to usb_modeswitch.