Uncertain Binary Thoughts

Weekend Project

Ankur Shrivastava — Wed, 10 Mar 2010 19:52:34 +0000

In Dec 2009 at foss.in at the maemo stall i saw a guy control a small toy car through accelerometer on his N900, i thought of replicating that but it just remained in my mind, so last Saturday i finally decided to implement it and went straight to a toy store and bought a toy RF car, one hour of hacking and i was able to control the small car through by phone (Nokia E61i) here is the video of it working.

the concept is simple, i send commands through my phone over wifi to my laptop which controls the car remote, controlling a toy car remote is very easy with a Parallel port and few transistors but laptops don’t have parallel ports, so i used a micro-controller in between to sort that out, so now micro controller controls the car remote by acting on signals received over UART from laptop.
the working is Phone —(WiFi)—>Laptop —(USB/UART)—> Micro controller —(Relays)—> Car Remote —(RF)—> Toy Car
will post details with code sometime later

strange thing in python

Ankur Shrivastava — Wed, 10 Feb 2010 12:52:17 +0000

i recently noticed this anyone has a proper explanation for this

for literals i get this
>>> def a(): ... b = [] ... c = {} ... >>> import dis >>> dis.dis(a) 2 0 BUILD_LIST 0 3 STORE_FAST 0 (b)
3 6 BUILD_MAP 0 9 STORE_FAST 1 (c) 12 LOAD_CONST 0 (None) 15 RETURN_VALUE

but for constructors i get this
>>> def a(): ... b = list() ... c = dict() ... >>> dis.dis(a) 2 0 LOAD_GLOBAL 0 (list) 3 CALL_FUNCTION 0 6 STORE_FAST 0 (b)
3 9 LOAD_GLOBAL 1 (dict) 12 CALL_FUNCTION 0 15 STORE_FAST 1 (c) 18 LOAD_CONST 0 (None) 21 RETURN_VALUE
i mean why the difference, i was thinking {} and dict() do the same thing, shouldn’t they?

Begining Python workshop

Ankur Shrivastava — Tue, 26 Jan 2010 21:09:33 +0000

LUG Manipal python workshop poster

LUG Manipal is organising a workshop on python, Workshop is aimed at people interested in beginning programming with python.No programming experience required.

Details are ->
Time: 5:30 pm
Place: NLH 103
Date: 29th JAN to 3rd FEB

PS :- Slides for the workshop are available Begining Python Slides

Mobi Vision 2.0 Slides

Ankur Shrivastava — Thu, 15 Oct 2009 12:30:55 +0000

First and Second Phase for MobiVision 2.0 is long over, and we can call it a workshop well done, the slides are here

Mobi Vision 2.0

View more documents from Ankur Shrivastava.

Getting started with pthread

Ankur Shrivastava — Thu, 24 Sep 2009 19:38:34 +0000

Recently i have started coding in C a lot and what i came across from a lot of people is that doing Threading in C is very hard, is it really like that? here is a simple Pthread program that should clear that up

get it here

in the above program i have just created 2 threads and passed thr1 ( = 1 ) and thr2 ( = 2 ) values as parameters the function void * thread ( void * ptr ) is executes as a separate thread, we create two thread objects thread1 and thread2, and start threads using pthread_create function passing thread object, function pointer and parameters as arguments, here NULL specifies default attributes for the thread, we can change this by passing pthread_attr_t structure instead of NULL.
we wait for the threads to finish using the pthread_join function
One major problem that is faced by most of the people is of using a library which is not a thread safe library, so you need to be careful about the libraries you use in your program, if not sure about a particular library being thread safe, just assume it not to be thread safe

PS – No updates from a long time as i dont have a proper net connection ….

A simple python socket chat example

Ankur Shrivastava — Wed, 29 Jul 2009 19:08:34 +0000

i was trying to explain sockets to one of my friend and this is what i used, the code should be self explanatory, this is a very simple application of sockets…

download here

How Manipal got its first Linux (fedora) server

Ankur Shrivastava — Thu, 25 Jun 2009 17:38:16 +0000

It all started with a failing Student’s Teacher Feedback System, designed by few fourth year students of my college, in oct-nov 2008 the system was not able to scale and everything was reverted back to paper, it was then when i was contacted by a teacher from my Department ( Information and Communication Technology ), regarding if i can improve it.

i asked DJ if he wants to join me and after few weeks of coding there it was Manipal university’s first (working) Feedback System, when the point of hosting it came, i was surprised to find Manipal University has no Linux servers, i mean come on no Linux what are you people click sys admins, then we decided to setup our own server in the department, thus giving Manipal university its first Linux ( fedora 10 ) server.

currently it just hosts the Feedback System, but we are planning to use it as local ( internal ) fedora repository mirror, we need permission from the WiFi provider ION because almost all the students use only WiFi and not LAN, last time we tried we were denied by saying ” You are a threat to our network “, lets see how it goes this time. we will also require people to manage it but i think this can be handled very well by LUG Manipal, some pics

Fedora 10 server in Manipal

PS – i am looking for a way to convince them that setting up a mirror will be helpful for them as well as students can anyone suggest me how to go about it??

Removing windows viruses from pen drives/HDD

Ankur Shrivastava — Mon, 15 Jun 2009 12:05:42 +0000

last week i gave my 250GB HDD to one of my friend and when i got it back it was filled with viruses, it was that virus which creates .exe inside every , since there were a lot of folders in the HDD ( it was 200GB full ) it was practically impossible for me to go and delete every virus in there, so i decided to make a simple script to remove these viruses here it is

Download here

PS – please be careful if you have windows programs they can also get deleted

Creating your own service like tinyurl

Ankur Shrivastava — Sun, 24 May 2009 09:45:56 +0000

Few weeks ago i came across this article on Techcrunch which says tinyurl is worth $46Million (of course before twitter started using bit.ly as default) which made me think how hard is it to make a simple service like tinyurl and i figured out its not hard. so i used apache’s mod_rewrite to rewrite the url and forward the code to a php script ( url.php ) which will then search for the url in database and take the use to the original url and for shorting, url it is inserted into a table with a auto increment primary key and the key is converted to base36 which contains [a-z] and [0-9], making the short code…

First create a database say ’shorturl’CREATE TABLE IF NOT EXISTS `shorturl` ( `id` int(11) NOT NULL AUTO_INCREMENT, `url` varchar(300) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
then create file .htaccess where you want your url to be and writeRewriteEngine On RewriteCond %{REQUEST_URI} \/([0-9a-z]*)$ [NC] RewriteRule ^(.*) url.php?url=%1 [L]

and to create the url we will use a simple file say create.php
Url Shortner ob_start(); $host=""; //host $dbuser=""; // database username $dbpass=""; // database password $db=""; //database name $con = mysql_connect($host,$dbuser,$dbpass); mysql_select_db("url",$con); if (!isset($_POST['shorten'])) { echo "

`Enter the url to shorten`

";

}

else

{

if (isset($_POST['url']))

{

$url=" ".mysql_real_escape_string($_POST['url']);

if (strpos($url,"http://") or strpos($url,"https://") or strpos($url,"ftp://"))

{

$url=mysql_real_escape_string($_POST['url']);

}

else

{

$url="http://".mysql_real_escape_string($_POST['url']);

}

$q="select * from url where url='{$url}'";

$res = mysql_query($q,$con);

$row=mysql_fetch_row($res);

if (!$row)

{

$query="insert into url set url='{$url}'";

$res = mysql_query($query,$con);

}

$query1="select id from url where url='{$url}' limit 1";

$res=mysql_query($query1,$con);

$row=mysql_fetch_row($res);

echo "shortened url is http://yoursite.com/".base_convert($row[0],10,36);

}

}

ob_end_flush();

?>

then our url.php file




ob_start();

$host=""; //host

$dbuser=""; // database username

$dbpass=""; // database password

$db=""; //database name

$con = mysql_connect($host,$dbuser,$dbpass);

mysql_select_db($db,$con);

if (isset($_GET['url']))

{

$query="select * from url where id ='".base_convert(mysql_real_escape_string($_GET['url']),36,10)."'";

$res = mysql_query($query,$con);

$row=mysql_fetch_row($res);

header("Location: ".$row[1]);

}

ob_end_flush();

?>

Download here

Get updates of completed torrents via SMS

Ankur Shrivastava — Mon, 06 Apr 2009 12:13:16 +0000

This Sunday when i was giving DBUS a look and thinking about all the cool things possible with it, one of my friend came asking how can he control his torrents from anywhere and i thought controlling is ok, do you want SMS updates??, i fired up qdbusviewer and there it was a simple way to get sms notifications of finished torrents using well twitter and ktorrent, so here are the steps
1) setup your cell phone to recieve SMS updates in twitter,
2) get one more twitter account lets say ktorrent, follow ktorrent and turn device updates on,
3) now save the script below say as torrenttwit.py
4) now enter this ktorrent account username and password in the script below,
5) start ktorrent if not already started, now run the script by typing “python torrenttwit.py”

import dbus,base64,urllib2,urllib
from dbus.mainloop.glib import DBusGMainLoop

DBusGMainLoop(set_as_default=True)
username="username"
password="password"

def tweet(msg):
        request = urllib2.Request('http://twitter.com/statuses/update.json')
        request.add_header('Authorization', 'Basic %s' % base64.encodestring('%s:%s' % (username,password))[:-1])
        request.add_data(urllib.urlencode({'status': msg.encode('utf-8')}))
        opener = urllib2.build_opener()
        req= opener.open(request)

s = dbus.SessionBus()
kt = s.get_object("org.ktorrent.ktorrent","/core")

def update(k):
        torrent = s.get_object("org.ktorrent.ktorrent","/torrent/"+k)
        name = torrent.get_dbus_method("name","org.ktorrent.torrent")
        tweet("ktorrent: finished " +name())

kt.connect_to_signal("finished",update)

import gobject
loop = gobject.MainLoop()
loop.run()

you are done, now whenever a torrent finishes the script will twit and you will receive an SMS update
enjoy

JavaFX and Pong

Ankur Shrivastava — Sun, 01 Mar 2009 17:38:03 +0000

There was a workshop conducted by engineers form SUN in our college regarding JavaFX, which went quite well. I was planning to start with JavaFX but as there was no Official release of any Linux SDK, it kept me back but this semester i had to install Windows because of my University which wants me to use Visual Studio for my mini project this semester, so as i had Windows (unwillingly) on my system i planned to go and attend this JavaFX workshop.
From what i have learned in these two days, JavaFX looks promising for developing Rich Internet Applications, the language is somewhat a mixture of JavaScript and Java. With Type Inference , Audio/Video support etc making it very easy to use and create applications with.
In the workshop after every thing was over we were asked to make a simple application in JavaFX, so here is my code for a Simple pong game in JavaFX
the resolution is set to 1440×900 you can change it to your resolution in the code

if you cannot see the code see here

PS – as i dont normally boot into windows i dont think that i will do anything in it soon, i am waiting for Linux JDK to be released…….

Using Apple Keyboard in Linux (Fedora)

Ankur Shrivastava — Wed, 18 Feb 2009 19:23:30 +0000

My Apple Keyboard

Few Days Ago i received my Apple Keyboard and i am enjoying typing on it, but having to hold down the Fn key then tap one of the F-keys to get F-keys working was irritating.
a simple solution to get it working just add this to your /etc/rc.local file



echo 2 > /sys/module/hid_apple/parameters/fnmode

and F-keys will start to work properly, enjoy

Update :- update for recent kernels,

ION proxy login problem

Ankur Shrivastava — Sun, 15 Feb 2009 19:59:10 +0000

a few days ago ION (WiFi provider in Manipal University) started an ISA based proxy using NTLM authentication, which according to them was a client install!!! some people were facing problem with it, like their browsers were asking for authentication (login) again and again, and repositories were not working on Linux.
So here is a simple screencast with solution for this problem it works great in Linux (esp. Fedora) i have also included configuring yum here, if someone wants to use apt-get (debian/ubuntu) they can do

export http_proxy=http://127.0.0.1:5865

Ok coming to the main point, go and download http://sourceforge.net/projects/ntlmaps/ and then watch the video here
People on windows can install python from here and then follow the steps
ION proxy problem solved
Note:- If You face any problem please post back here….
PS:- every thing in Text form coming soon… (i am lazy)

HowTo MPD with Pulse audio

Ankur Shrivastava — Fri, 13 Feb 2009 17:52:23 +0000

A Little background, i just shifted to mpd from Amarok 2.0 somewhy i dont seem to like Amarok 2 but thats a different story, For those who dont know MPD s a flexible, powerful, server-side application for playing music. which runs as a daemon and has a lot of front ends for it, Sonata being a popular one.
now coming to the point i use Fedora 10 and it has Pulseaudio by default, now the problem is i some time get “NO Read Permission” in Sonata and then mpd would stop working, in mpd.log file i will find “Error opening ALSA device “hw:0,0″: Device or resource busy” error, which means this is an pulseaudio permission issue, to solve it we need to change the mpd.conf (/etc/mpd.conf) to
audio_output { type "pulse" name "My Device" device "hw:0,0" # optional format "44100:16:2" # optional }
then we need to add
load-module module-native-protocol-tcp auth-anonymous=1
to /etc/pulse/default.pa which gives everybody permission to use pulseaudio and thats it.

LUG Manipal’s Python Workshop

Ankur Shrivastava — Mon, 26 Jan 2009 07:56:13 +0000

Python Workshop Poster

LUG Manipal is organising a workshop on Python, which is a dynamic object-oriented programming language that can be used for many kinds of software development. It runs on Windows, Linux/Unix, Mac OS X, OS/2, Amiga, Palm Handhelds, and Nokia mobile phones. It comes with extensive standard libraries, and can be learned in a few days.
The workshop requires no prerequisites, even knowledge of C is not required, it is aimed at people interested in beginning programming with Python.
There is no charge for the workshop and no registration is required, everyone is invited.
People using Windows are requested to Install the Following Software before coming to the workshop
1) Python 2.6.1 from here
2) Notepad++ from here

Note: These will also be distributed on the first day of the workshop, If you are not able to install/download them you can get them there…