Thursday, March 19, 2015

(Linux/Ubuntu) Frequent 802.11g/WPA2 connection drops with brcmsmac/BCM4313 driver

My Samsung laptop running Ubuntu 14.10 has been dropping its WiFi connection a lot. A cursory examination of the system log reveals that it usually happens once every 20-40 minutes, with a few suspicious cases where it dropped and re-established the connection after exactly 25 minutes:
$ grep "wlan0: associated" /var/log/syslog.1
Mar 17 20:45:48 gravitycat kernel: [101379.946156] wlan0: associated
Mar 17 21:10:48 gravitycat kernel: [102880.685412] wlan0: associated
Mar 17 21:33:32 gravitycat kernel: [104244.524634] wlan0: associated
Mar 17 21:43:03 gravitycat kernel: [104815.501396] wlan0: associated
Mar 17 22:08:03 gravitycat kernel: [106316.384463] wlan0: associated
Mar 17 22:11:23 gravitycat kernel: [   35.255877] wlan0: associated
Mar 17 22:46:55 gravitycat kernel: [ 2167.317562] wlan0: associated
Mar 17 23:29:08 gravitycat kernel: [ 4701.239455] wlan0: associated
Mar 17 23:54:08 gravitycat kernel: [ 6201.802957] wlan0: associated
Mar 18 00:00:26 gravitycat kernel: [ 6579.424244] wlan0: associated
Mar 18 00:25:26 gravitycat kernel: [ 8080.034656] wlan0: associated

The connection drops usually looked like this:
Mar 17 22:08:03 gravitycat NetworkManager[785]:  Connection disconnected (reason -4)

But were sometimes preceded by this:
Mar 18 01:09:43 gravitycat kernel: [10736.798220] wlan0: cannot understand ECSA IE operating class 33, disconnecting

It alternates between "class 33" and "class 12". After a tiny bit of digging, I found a suggestion here to try switching from Gnome's NetworkManager to WICD. At first, that seemed to make things better, but it started happening again after about an hour, with the same really frustrating behaviour (having to repeatedly queue the same videos on my Chromecast when it sees me "leave" due to the laptop dropping and reconnecting to the router).

Next port of call is to check the driver. Here's what lspci says is installed in my laptop:
$ lspci -vvnn | grep -A 9 Network 
03:00.0 Network controller [0280]: Broadcom Corporation BCM4313 802.11bgn Wireless Network Adapter [14e4:4727] (rev 01)
 Subsystem: Askey Computer Corp. Device [144f:7179]

For this device, Ubuntu defaults to the "brcmsmac" open source driver, which is always preferable to a closed-source proprietary driver, all other things being equal. This issue is so frustrating, however, that I'll take the closed-source "bcmwl" driver if it works, following these steps:
$ sudo apt-get install bcmwl-kernel-source
$ sudo modprobe -r brcmsmac bcma
$ sudo modprobe wl

After manually reconnecting with WICD, things seem stable and the ChromeCast hasn't bailed over the past day or so. It's a shame the open source driver isn't working well with the BCM4313 chipset. It'd be nice if there was a simple way to get started debugging/testing the driver – i.e. not having to download a massive tarball of the latest kernel source and spend hours tweaking with build scripts and the like. Unless things have changed in the last few years and now this is easy...?

Monday, February 09, 2015

OpenCV 2.4.10 and Macports

Every time I've needed to build OpenCV on my work Mac, it's been a bit of a struggle. I have Macports installed which helps make some things easier, but throws up problems of its own:
(using "mp-gcc49")
/Users/oisin/Documents/code/vision/opencv-2.4.10/modules/highgui/src/ In function 'void cvDestroyAllWindows()':
/Users/oisin/Documents/code/vision/opencv-2.4.10/modules/highgui/src/ error: expected ';' before 'in'
     for(NSString *key in list) {

(using "apple-gcc42")
/System/Library/Frameworks/QTKit.framework/Headers/QTMovieModernizer.h:123:46: error: expected ')' before '(' token
- (void)modernizeWithCompletionHandler:(void (^)(void))handler AVAILABLE_QTKIT_VERSION_7_7_3_AND_LATER;
/System/Library/Frameworks/QTKit.framework/Headers/QTMovieModernizer.h:123:46: error: expected identifier before '(' token

The problem appears to be Objective-C stuff in QTKit and in OpenCV's HighGUI code. This time, the solution was to revert to the system-default C/C++ compiler, Clang:
$ sudo port select gcc none
Warning: port definitions are more than two weeks old, consider updating them by running 'port selfupdate'.
Selecting 'none' for 'gcc' succeeded. 'none' is now active.

It's slightly counterintuitive that "port select gcc none" is how you go back to the system compiler with Macports, and it doesn't appear to be stated in the docs, so... well here it is!

Sunday, July 27, 2014

A tiny line-editing trick for Bash (or any REPL using Readline/emacs bindings)

A lot of shells (e.g. Bash) and interactive console programs (e.g. mysql, sqlite, ghci, irb) provide a line-editing interface based on Emacs bindings, either via the Readline library or similar.

These key bindings mostly take the form of ESC-<key> which is either an uncomfortable stretch or (on a full-size keyboard) takes your left hand away from the home row and slows you down. Here's a handy tip though: pressing Ctrl+[ is equivalent to hitting escape, but allows you to keep your hands on the keyboard's home row. And if you're lucky, you can hold the Alt key instead (so you can jump backwards with Alt-b and delete the next word with Alt-d — this works on Gnome Terminal for me at least, except where the key is one of the menu accelerator characters (f, e, v, s, t or h). Seriously though, until today I was hitting ESC then the desired key...

Thursday, September 26, 2013

Ralink RF3070 USB wireless support finally added to Linux

For a long time, these cheap Chinese USB wifi adapters didn't work in Linux. Believe it or not, I wiped my old laptop's Linux partition and tried FreeBSD and OpenBSD just to see if they supported it - but they didn't either.
So I reinstalled Linux and eventually produced a patch back in June to add support for the device, but for whatever reason it was ignored.

Now, though, one of the maintainers has implemented a proper patch and it looks like the RF3070 will soon work out-of-box in Linux.


Monday, May 13, 2013

OpenCV build: "Could NOT find JNI" (Ubuntu)

While trying to build OpenCV so I could use the new Java bindings, I kept getting this somewhat confusing message:

What does it mean - did I need to set environment variables for the AWT and JVM libraries? Surely they're both already installed. What does it even mean to say "Could NOT find JNI", since JNI is a part of Java which is installed?

Turns out I needed to manually set the JAVA_HOME environment variable:
export JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-amd64
Why Ubuntu doesn't automatically set this when you install the openjdk7 package, I have no idea.

Sunday, February 24, 2013

Eye queue

This comment by "Cabochon1360" on one of David Mitchell's Youtube videos struck me today (far more than the video), and sums up my own feelings better than I could have.
In my teens, I was proud of my allegedly high IQ. But decades of failures and other humbling experiences have shown me it's just one personal characteristic, and not the most important one.
Another thing to bear in mind is that telling your kids they did well on a test because they're smart hinders their future performance. Perhaps counter-intuitive but it's been demonstrated in a number of studies (even when performed on adults, AFAIK).

Friday, July 20, 2012

What did I miss about modern Linux?

After running Windows alone for a couple of years, I had to install a Linux distro yesterday since the CUDA API in Windows is pretty ridiculous, flat out refusing to work with MinGW (the Windows port of gcc/g++ and pals).

Although I wasted a lot of time trying to get my dumb Medion PC (MS-7358 mainboard) to boot from two different USB keys, eventually a blank CD turned up and Ubuntu 12.04 landed on it. The install was quick, and this time (unlike on the old Acer laptop my kid uses) the Nvidia card was supported better, giving a usable display.

I needed to install some tools first before getting the CUDA API/SDK/drivers on Ubuntu:
The following NEW packages will be installed:
  build-essential dpkg-dev freeglut3-dev g++ g++-4.6 libalgorithm-diff-perl
  libalgorithm-diff-xs-perl libalgorithm-merge-perl libdpkg-perl libdrm-dev
  libgl1-mesa-dev libglu1-mesa-dev libice-dev libkms1 libpthread-stubs0
  libpthread-stubs0-dev libsm-dev libstdc++6-4.6-dev libtimedate-perl
  libx11-dev libx11-doc libxau-dev libxcb1-dev libxdmcp-dev libxext-dev
  libxi-dev libxmu-dev libxmu-headers libxt-dev mesa-common-dev
  x11proto-core-dev x11proto-input-dev x11proto-kb-dev x11proto-xext-dev
  xorg-sgml-doctools xtrans-dev
0 upgraded, 36 newly installed, 0 to remove and 0 not upgraded.
Need to get 15.3 MB of archives.
Fetched 15.3 MB in 3s (3,835 kB/s)
Setting up build-essential (11.5ubuntu2) ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Now I really wish I'd prefixed this with the "time" command, because it took far less than a minute - maybe 15 to 30 seconds to install all of this... the C++ compiler, X11 libraries and a bunch of other stuff.

In contrast, it took a good 5 minutes just to install Visual Studio 2010 on my Windows 7 laptop (a 64-bit box with a better CPU than this desktop) and the library problems cost me a couple of hours of headbanging which was never resolved.

There are still serious driver problems in Linux, but the whole experience has improved so much since I started with a Red Hat install back in 1998.
Being able to install any number of programs and libraries rapidly, with a single command, is so much more relaxing than trying to hack things together in Windows. Try it!