bana's blog

Fixing electric hair clipper

2015-12-23T22:11:00Z

Right now, before christmas day my electric hair cutter is broken. The adapter has fall down and this shit is not working anymore, the little red led is absolutely not blinking. So the cable is useless.

Setting up Raspberry PI as webserver

2013-10-15T17:36:00Z

Finally I have decided that sharing my collected notes and put it into some readable format. Yes, the Raspberry PI craziness that nowdays sweep through the internet touched me as well. I could not just pass it and not get one. I have ordered the RPI Model-B rev-2 version with 512Mbyte of RAM, 4Gb SD card and passive coolers. Actually I wanted to use it as own webserver and creating a blog which running on the machine. Because I thought it would be cool sometimes use it to playing films just wanted to connect it to my Samsung TV through HDMI. Of course not to use it uncomfortable directly keyboard and mouses but get the X layout of RPI from remote desktop.

Motivation and decision

Small board, impressive, attractive and cheap computer.
Hackable Linux based platform provided with ATM chipset.
Low electricity consumption.
Silent machine with possible passive cooler.

Own webserver. It’s not on the other side of world holding a 3th party ownership.
Mini file server for notes and not too large files.
Reusable for several projects.
Hardwer and software in one hand. ☺

Simple box for RPI

I prefer the simple but clever solution. I was seeking something easily accessible box for RPI and surfed the web when I found a creative but easy solution: LEGO. On the net there are lot of cool skins for RPI but just spent some hours to looking for my old LEGO pieces and started to build it.
The RPI board fits in a LEGO enclosured box with dimension of 9 x 13 blocks. Perfect. Because Raspberry PI is small still with the box, the best place was it to me put it behind the TV. It can be easily connected to TV through HDMI. Because the on the board there is not any cooling solution I have also bought a passive coolers whiches just had to stick on the chips. In the most RPI stores can be ordered a prepared package contains three passive coolers for every important chip on RPI board. Some picture when I have got it and about the result.

Doing the software way..

There is a set of compatible operating system to RPI for different purposes. At first testing I have just installed the most popular Debian Wheezy system with X layout. Because it may exists better OS for my purposes (e.g. running only webserver I would use the faster Risc OS) but I did't want to reinstall a new one so it remained. Download OS here and how-to burning the image on SD card can be found here.
Let's do the necessary settings, install the softwares and libraries.



passwd                        # change password from 'pi'/'raspberry' to new one

date +%T -s "20:58:00"        # set time

dpkg --get-selections         # checking what we may need to have

sudo apt-get update           # get recommanded software updates

sudo apt-get install xrdp     # server for remote desktop protocol

sudo apt-get remove nano      # remove unnecessary sofwares ...

sudo apt-get install vfstpd   # secure and fast FTP server

sudo vi /etc/bash.bashrc      # write psg="ps -aux | grep" to use psg alias

!FTP 550 permission upload    # problem solving

!sudo vi /etc/vtftpsd.conf

!sudo service vsftpd restart

Use this one to know what happens on RPI because the programs are installed here logging in this file.


tail -f /var/log/messages           # always checking knowing problems

Installing Virtual Network Computing program (VNC) to handle RPI from remote.


sudo apt-get install tightvncserver # get the VNC server to get new X displays
!vncserver :1 -geometry 1280x800 -depth 16 -pixelformat rgb565: # start
!sudo chown pi /home/pi/.Xauthority # problem solving
!vncpasswd view-pass NONONO         # recover password
sudo apt-get install x11vnc         # get the real X displays
!startx&                            # start X desktop
!vncserver                          # start VNC
!x11vnc                             # start X11VNC
!# From now you can connect with vncviewer on 0 display to get real RPI display

Testing pendrive. I had no problem the automount worked well on X display and the a folder came up.


/kernel/sda/sda1                    # the path of automounted pendrve

On the net there is a lot of available webserver on different size and for different purposes. Because of RPI is not made of running heavy webservers I wanted to spare with the load and space (my SD card is only 4GB). And earlier I have decided that I want to create so kind of blog that does not need database and as it possible it avoids the dynamically elements. Decision to lightweight webservers. Comparsion of lightweight webservers. Here you can find a cool analysation of lightweight webservers. May it recommended from RPI community? Nginx (6,2000Kb on my SD card).


sudo apt-get install nginx         # get nginx webserver
sudo useradd www-data              # user grant to user of webserver(s)
sudo groupadd www-data             # group grant to user of webserver(s)
sudo usermod -g www-data www-data  # changing user group of user
!/usr/share/nginx/www/             # path to put the pages

Mplayer, setting sound

Playing films and music or just listening to radio, do the compulsory settings.


sudo apt-get update
sudo apt-get upgrade
sudo apt-get install mplayer mplayer-gui alsa-base alsa-utils pulseaudio mpg123
sudo usermod -aG video pi
sudo amixer cset numid=3          # http://elinux.org/R-Pi_Troubleshooting
mplayer -fs xy.avi                # fullscreen mplayer from consol
mplayer -ao alsa -playlist "http://88.151.102.84:8003/mp3.m3u" # FM online radio

Blogging motor

On this section I don’t want to waste the time to reason why it’s good keeping the things as simple as posible but one of the possible way to do it with static blog generator. My requirement was a quite high performance blog platform, track content changes easily, writing posts (using Markdown), publish them in easy format but still holding posts in logic structure like a blog. I wanted to eliminate the complex and large webservers (as I did it with nginx) so being on this way wanted to do it with blogging method as well. There is no need dynamic websites, frameworks systems (CMS), database request and other overheads, instead of them just using static HTML pages.
The other reason is when once I would like to move on or whatever editing the contain I just simple handle it. No database requests from several tables, no different technology chaos to put the contain in readable format, no dynamic pages, no annoying porting necesseries. Small size, python script, more than enough to my purposes.
A simpatic static generator: Mynt. Mynt supports custom date, tag-based archives, Markdown posts, Jinja templates and YAML front matter.
First I had some problem with different mynt versions and got python compile errors. Because I could not find the solution on forums, in IRC channel Anomareh the developer of mynt helped me to fix it. I was using mynt 0.2.2 instead of 0.2.3 with jinja 2.7.


sudo apt-get install nedit            # get text editor with highlightings
sudo apt-get install git
sudo apt-get install python-dev
sudo apt-get install python-pip
sudo pip install mynt                 # get static site generator

Static address for global access

Okey! We got webserver, blogging platform and so static HTML pages. Open the door and make it available from internet. If you want to use free DNS, register at on of the free dynamic DNS service and get a simpatic domain name. I’ve used this one: http://freedns.afraid.org.
Install ddclient client used to update dynamic DNS entries for accounts on Dynamic DNS Network Services' free DNS service. When it is done and the settings are correct, go to settings menu of your router (e.g: 192.168.1.1) and create an open port (do port forwarding) that allow a connection in to your home network from the Internet. To get to know your external IP and port using RPI, here is a site (port 80 for webserver).
More details about the port forwarding at specific router check this site.


sudo apt-get install ddclient         # get ddclient
sudo vi /etc/ddclient.conf            # protocol=dyndns1, server=freedns.afraid.org, login and password
sudo vi /etc/default/ddclient         # run_deamon="true", run_ipup="true"

Commands make sense

Some commands I was using during the installation process, they may be helpful.


mynt --version                        # current version of mynt
mynt init ~/src                       # initializing new site
mynt watch -f src/ res/               # automatic regeneration after site modification
du -ch                                # current files total in readble format (Kb, Mb, etc.)
df -h                                 # filesystem disk space usage in readable format
shutdown -r now                       # restart rpi
shutdown -h now                       # halt rpi
/opt/vc/bin/vcgencmd measure_temp     # GPU temperatur
/sys/class/thermal/thermal_zone0/temp # CPU temperatur (is the first two digit)
sudo apt-get install vnstat           # network traffic, vnstat --dumpdb
sudo cat /var/log/nginx/access.log    # nginx log about visitors
netstat -t -u                         # TCP and UDP connections

Experience

My RPI has been running for 3 months without problems. Sometime I’ve checked and cleaned the dust around the box that was until now the maintenancing. The webserver is also working well but of course it is not sized to heavy-load. I think to get the passive coolers was also a good idea. Sometime I’ve checked the temperatur of chips (or just touched them with finger) and after a film watching, of course an active using it was really hot with the passiv coolers as well. What’s else would be without them?!

To powering RPI I use a typical Samsung charger and had never problem with that. (On forums it can be read about some cheap and after made charger which is not workign appropiate e.g.: problems reading pendrive or not powering the RPI.)

Useful links

Playing videos with L32D400 Samsung TV

2013-09-15T15:14:00Z

Last weekends I’ve played with my Raspberry PI and looked for descriptions to switch on/off the TV through HDMI using CEC technology. Unfortunately our Samsung TV is not provided CEC so had to give up my project but during reading forums I found a very interesting feature of Samsung TV.

On our Samsung TV (model type: LE32D400) the function to play videos is denied but only in software way. So when you get into the menu you can not see any icon to play videos. I’ve just set the type of TV to LD451 in service menu and voila I can play the video files.
How to do it: turn off the TV in stand by and with the key sequence INFO + MENU + MUTE + STANDBY + OK (from remote in quite fast order) to get in the service menu to change the parameter MODEL to LD451. Now press RETURN key (from remote) and turn off the TV again. Press on CONTENT (from remote) or just put a pendrive in USB contains e.g. avi files it’s automatically come up the possible of playing videos.

I’ve tested the media player only with AVI and MVK files they are just working fine. Tried to play videos with subtitles SRT and SUB but the media player could not played them. The media player can do the ordinary functions (search forward and backward, stop, pause and jump to exact time). But after jumping to exact time or searching forward there is sometime lagging at playing or the sound going away for some seconds. It may occur by weak buffering so I do not recommend to use search function but otherwise the media player is really useful. And here is a link to the forum may you find more information.

Simple showing of file processing in Perl

2013-09-06T10:48:00Z

Today I had to create script in Perl that processing quite long textbased files and convert new ones. Because sometime it takes long time I wanted to give some information to the script-user how many percent is executed of input file by script. I wanted a simple solution (and do not take the implementation more than 20 minutes including the googling) so just update the percentage on terminal window always in the same line.
Damn simple but informative!


#!/usr/local/bin/perl
..
my $InpFil = $ARGV[0];
my $g_num_of_lines = `wc -l <$InpFile`; #the number of lines in input file   
my $g_cur_of_lines = 0;                 #current line during processing
my $g_cur = 0;
..
open (IN, $InpFile);
while(){
    ...
    ...
    displayPercent();
}
close(IN);
...
...
sub displayPercent{

  if(eof(IN)){
    print "Processing is done.\n";
  }else{

    #percent calculation and round numbers to be remained on the same place   
    $g_cur = sprintf("%.2f", ($g_cur_of_lines++ / $g_num_of_lines)*100); 

    #refreshing and '\r' get to start of current line
    print "$g_cur %\r";

  }
}

2038 structure time_t in C

2013-08-22T18:22:00Z

Today on my workplace when I was looking for some details about the well-known time_t and other data structure conversion came across this problem. I won’t say I have never heard about it or even would be a daily problem but as I am checking our systems in that year 2038 some percent of companies and so one part of programmer society will get a fix job to prepare the old running systems and programs for change. What kind of change? Here is a plain article from the Informationweek portal. Or more details on Wikipedia site.

25 years from today, January 19, 2038, at 03:14:08 UTC, an odd thing will happen to some of the no doubt very large number of computing devices in our world: an old, well-known and well-understood bug will cause their calculation of time to fail. The problem springs from the use of a 32-bit signed integer to store a time value, as a number of seconds since 00:00:00 UTC on Thursday, 1 January 1970, a practice begun in early UNIX systems with the standard C library data structure time_t. On January 19, 2038, at 03:14:08 UTC that integer will overflow, as demonstrated in this animated GIF:

This problem is also actually cool. When you want to earn money now (or maybe a little bit later) it is a possible chance to launch out on an enterprise that specialize to fix this kind of problem. No risk, the problem will come up. Honestly I must say before the year of 2000 was also a good chance for computer specialist to announce that our computers and programs are prepared yet for the next millenium so way get more extra fees in the pockets. I can still remember before the year of 2000 when just got a new desktop machine on that was a little glued stamp it announced proudly ‘Y2K safety’. More about Y2K.

And of course I've almost forgotten to give a new tag to article as disaster. I do not think so that it will be one (like Y2K when it had much smoke little fire, at least for the perfectly ordinary people). But I am curious yet which film studio will be the first one that announce a film around this theme when the computers crash so destroy our ordinary life.

Playing experiment with Ngram Viewer

2013-08-16T19:10:00Z

Today a daily-news portal recommended a not so known Google service the Ngram Viewer. In fact I have never heard about that before but suddenly I have been really curious to play with that some minutes. The service is about to chart the yearly count of selected words or phrases as found in more than 5.2 million books digitized by Google Inc. Ngram name refers to n-gram that is a finite sequence of n items from a given sequence of text (e.g.: it can be words, phrases or text-parts). This way it’s possible to generate talkative diagrams in the requested year-range just the keywords must be choosen clever way.

What’s telling the books about things in last years?! Let’s do a little experiment with Ngram Viewer and check the result of generated diagrams with a slight sense of humour.

Typewriter and computer. After the invention..

Tamagotchi and tetris. The ‘tetris’ word as latin word was found in set of publications in the last century but after today’s called classic Tetris game showed up. Later the crazy spreading of Tamagotchi the Japan digital pet.

Capslock and numlock. Depending on the spelling..but which one is the more popular?!

Transistor vs. chip. All in due time.

Horse and car. After the invention..

First post

2013-08-16T14:22:00Z

Be this the first post and giving new tags to tag cloud. Nothing else.