Avinash Meetoo: Blog

Someone said that Linux was progressing only through sheer luck… And this make Linus Torvalds react:

And don’t EVER make the mistake that you can design something better than
what you get from ruthless massively parallel trial-and-error with a feedback cycle. That’s giving your intelligence much too much credit.

Linus was referring to the open source development model (have you read The Cathedral and the Bazaar? You really really should!) compared to the classical corporate model of software development.

And, of course, he is right.

Popularity: 2% [?]

written by avinash

Emtel has recently started selling a USB modem (a Huawei E220) which uses its 3G cellular network (specifically HSDPA) to provide an Internet connection of up to 1.8Mbits/s.

A good friend of mine has bought one for his company but has not been able to make it work with Linux. Always looking for a new technical challenge (yes, I am a geek), I told him that I was willing to give it a try during the week-end. And this post is about what I did to make it work.

I run Kubuntu 7.10 (with kernel 2.6.22 which is > 2.6.19 which means that everything should normally work out of the box). Of course, this was mostly true in my case. Here is the exact version of Linux I’m using:

Linux noulakaz 2.6.22-14-generic #1 SMP Sun Oct 14 23:05:12 GMT 2007 i686 GNU/Linux

Plugging the Huawei E220 and typing dmesg, I get:

[ 112.528000] usb 2-1: new full speed USB device using uhci_hcd and address 2
[ 112.688000] usb 2-1: configuration #1 chosen from 1 choice
[ 112.796000] usbcore: registered new interface driver usbserial
[ 112.800000] /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/serial/usb-serial.c:
USB Serial support registered for generic
[ 112.800000] usbcore: registered new interface driver usbserial_generic
[ 112.800000] /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/serial/usb-serial.c:
USB Serial Driver core
[ 112.808000] /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/serial/usb-serial.c:
USB Serial support registered for GSM modem (1-port)
[ 112.812000] option 2-1:1.0: GSM modem (1-port) converter detected
[ 112.812000] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB0
[ 112.812000] usbcore: registered new interface driver option
[ 112.812000] /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/serial/option.c:
USB Driver for GSM modems: v0.7.1
[ 112.824000] usbcore: registered new interface driver libusual

Of course, the important information here is:

GSM modem (1-port) converter now attached to ttyUSB0

In /dev, the following device is created automatically:

crw-rw—- 1 root dialout 188, 0 2007-12-16 10:24 ttyUSB0

BIG PROBLEM!

/dev/ttyUSB1 and /dev/ttyUSB2 do not exist meaning that the modem won’t respond. After searching, I found the solution online on Mohd Shakir Zakaria’s weblog. The solution is to remove the uhci_hcd kernel module, reload it and wait for ttyUSB1 and ttyUSB2 to be created (this looks like a bug in uhci_hcd) [Thanks to Shakir who sent me a mail to tell me that uhci_hcd only has to be removed and reloaded once for the appropriate devices to be created...]

sudo modprobe -r uhci_hcd
sudo modprobe uhci_hcd

and the following is logged after some time:

[ 776.960000] option 2-1:1.0: GSM modem (1-port) converter detected
[ 776.960000] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB0
[ 776.964000] option 2-1:1.1: GSM modem (1-port) converter detected
[ 776.964000] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB1
[ 776.968000] option 2-1:1.2: GSM modem (1-port) converter detected
[ 776.968000] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB2

There is a script which automates this process.

Connection to the Emtel network using wvdial is then trivial. This is my wvdial.conf:

[Dialer Emtel]
Phone = *99***1#
Modem = /dev/ttyUSB0
Username = user
Password = pass
ISDN = 0
New PPPD = yes
Baud = 1843200
Init2 = ATZ
Init3 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = Analog Modem

Running:

sudo wvdial Emtel

produces:

WvDial<*1>: WvDial: Internet dialer version 1.56
WvModem<*1>: Cannot get information for serial port.
WvDial<*1>: Initializing modem.
WvDial<*1>: Sending: ATZ
WvDial Modem<*1>: ATZ
WvDial Modem<*1>: OK
WvDial<*1>: Sending: ATZ
WvDial Modem<*1>: ATZ
WvDial Modem<*1>: OK
WvDial<*1>: Sending: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
WvDial Modem<*1>: ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
WvDial Modem<*1>: OK
WvDial<*1>: Modem initialized.
WvDial<*1>: Sending: ATDT*99***1#
WvDial<*1>: Waiting for carrier.
WvDial Modem<*1>: ATDT*99***1#
WvDial Modem<*1>: CONNECT
WvDial<*1>: Carrier detected. Waiting for prompt.
WvDial<Notice>: Don’t know what to do! Starting pppd and hoping for the best.
WvDial<Notice>: Starting pppd at Sun Dec 16 10:35:57 2007
WvDial<Notice>: Pid of pppd: 6193
WvDial<*1>: Using interface ppp0
WvDial<*1>: local IP address 10.11.80.28
WvDial<*1>: remote IP address 10.64.64.64
WvDial<*1>: primary DNS address 196.192.4.4
WvDial<*1>: secondary DNS address 213.200.89.89

I tested the Huawei E220 by downloading a couple of my own MP3s:

time wget http://www.noulakaz.net/avinash/music/so-logical/07-play.mp3
Length: 4,879,827 (4.7M)
real 2m5.443s

The download speed is 304 kbits/s

time wget http://www.noulakaz.net/avinash/music/so-logical/04-helium.mp3
Length: 4,276,087 (4.1M)
real 2m5.200s

Download speed is 267 kbits/s

And I also downloaded a 6Mb file from an official Ubuntu server:

time wget http://mu.archive.ubuntu.com/ubuntu/ls-lR.gz
Length: 6,000,019 (5.7M)
real 4m35.690s

Download speed is only 170 kbits/s which is nothing to shout about - but, at least, it works

6 January 2007: an update

I’ve added sudo everywhere because I’ve realized that many Ubuntu (or Kubuntu) users do not know how to log in as root (which is excellent ). I’ve also used dmesg command instead of having a look in the log files directly.

Popularity: 3% [?]

written by avinash

I have a decent home cinema at home. For many years, I did not use a subwoofer for low frequencies but I’ve just decided to get one. I’ve chosen the Sony SA-W2500 (pictured above) as it seems to be ideal for me: powerful yet cheap.

Unfortunately, I don’t think I’ll manage to get one in Mauritius. I’ve been to many “electronic” shops and I have not been lucky.

In one shop in Rose-Hill, they had another (excellent) brand. Unfortunately, they were selling it at around 4-5 times more than it costs on Amazon.com…

In another shop at Phoenix, the vendor told me that they don’t sell subwoofers as a separate component but rather as part of a complete 5.1 system together with an amplifier. He did seem aware that Sony had a number of standalone subwoofers in its catalogue…

I think I’ll have to continue my quest until the 24th… Anyone knows where I can find a shop selling subwoofers at realistic prices in Mauritius?

Why?

Some people have asked me why I’m looking for a subwoofer even though they felt that my existing speakers were good enough. The reason is this:

My amplifier features an automatic calibration system which automatically equalizes each speaker to (try to) produce a relatively flat response. The EQ above is for my front left speaker. The amplifier has determined that 40Hz should be boosted by 6 dB while 125Hz reduced by 6 dB. This looks very bad to me. The first rule of EQ is that thou shall never boost too much. Therefore, it is evident that there is something missing in the equation: yes, a subwoofer! The cheap Pioneer speakers that I use, simply, can’t reproduce low frequencies!

I really need a subwoofer! But will I ever get one?

Popularity: 1% [?]

written by avinash