Migrated!

I have decided to migrate blogging over to jekyll + github-pages. They can be found here.

Eclipse ADT: 'Unable to open sync connection!'

Sometimes, you get this wierd looking error on eclipse while working/developing on your phone.

[2010-10-12 09:36:48 - myapp] java.io.IOException: Unable to open sync connection!
[2010-10-12 09:36:48 - myapp] Launch canceled!

You have tried the following (but in vain!):
1. Disconnecting/connecting the USB cable.
2. Restarting eclipse.
3. Restarting adb daemon.
4. Restarting your computer!


Even after this if the problem persists. Just disable/enable 'USB debugging' on your phone.
This should most of the times solve this issue.

A short perl code to find union of 2 arrays in perl

Using slices on hash variable :)

sub array_union {
    my ($arrRef1, $arrRef2) = @_;
    my %hash;
    @hash{@$arrRef1} = undef;
    @hash{@$arrRef2} = undef;
    return keys %hash;
}

Upgrading CM7 on LG O2X

If you are planning to upgrade CM7 on your LG O2X, please make sure you have done the following!
Upgrade clockworkmod to a version >= 5. (You can do this from 'ROM Manager' itself)

ARFF file-reader in C++

Long time ago I had written a C++ library to parse ARFF files for one of my Machine-Learning projects. Today, I'm making the code open-source! Here's the link to the code hosted on github: https://github.com/teju85/ARFF. This also comes with doxygen documentation for the API exposed by this library and also has unit-tests (written using google-test) for CYA.

Iterator for templated STL containers in C++

I realized this today! The following code almost always will give compilation error.

std::vector::const_iterator itr;

And the compilation error (with g++ version 3.4.6) will be as vague as:

error: expected `;' before "itr"

The solution is to just do the following:

typename std::vector::const_iterator itr;

Getting (approx?) memory usage information on linux

Here's the code for doing so: (Tested on Ubuntu 10.10)

#include <unistd.h>
#include <stdio.h>
int processMemUsage() {
    int vm = 0;
    FILE* fp = fopen("/proc/self/stat", "r");
    if(fp == NULL) {
        return vm;
    }
    int dummy;
    char cmd[128], state[8];
    fscanf(fp, "%d%s%s%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d",
           &dummy, cmd, state, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy);
    unsigned long vmSize;
    fscanf(fp, "%lu", &vmSize);
    fclose(fp);
    vm = (int) (vmSize >> 10);
    return vm;
}

Hope this helps!

How to request 'super user' permission from your app?

NOTE: This blog assumes that you have installed Superuser application installed on your device! Also, I'm not responsible for any bricked devices!

Process p;
try {
    p = Runtime.getRuntime().exec("su");
}
catch(IOException e) {
    e.printStackTrace();
}

This will pop up a window from 'Superuser' application which will ask user to whether allow your app to be given 'su' permissions or not. Users can either 'Allow' or 'Deny' and also set 'Remember this option' on this window.

Hope this helps!

AdbCommandRejectedException!

Sometimes, adb goes crazy on my Win7. If I open 'ddms' (to view logcat messages), I wont see any messages at all! If I look into the 'Command Window', I see the above exception being raised in it. Apparently, the work-around this is to do the following:

1. Un-plug the USB cable.
2. Kill the adb-server (adb kill-server)
3. Start the adb-server (adb start-server)
4. Plug in the USB

 Hope this helps!

Camera shutter sound on CM7!

Due to legal issues in some countries (see this issue) cyanogenmod doesn't support any settings for enabling/disabling camera shutter sound (It is enabled by default!). However, there's a system property which one can set in order to turn off the shutter sound. But, unfortuantely for this you need to install android SDK on your system and plug USB cable to your phone and connect it to your PC. (Also, do not forget to 'enable USB debugging'!!).

  adb shell setprop persist.camera.shutter.disable 1

NOTE:

 I'm not responsible for any damages/law-suites caused (whatsoever), by disabling the shutter sound of your phone's camera!

Measuring read/write BW of sdcard(s) on your android phones

I needed a quantitative way to measure the performance of the sd-card on my LG Optimus 2X. Hence I wrote the tool 'sd-speed'. Currently, this tool is supported only on linux and windows platforms. The project is hosted on github at the following location: 'git@github.com:teju85/sd-speed.git'. I have released it with the WTFPL (do What The Fuck you want to Public License).

Here are the results of running my program on my 'external sd-card', 'internal sd-card' and on 'phone memory' respectively: (Phone: LG O2X, CM7)

External sd-card

$ ./sdCardSpeedTest.sh /mnt/sdcard
NOTE: Test might take about 5-10 min depending on your sd-card speed!
      Please be patient during this time...

Evaluating write-BW...
100000000 bytes transferred in 26.371 secs (3792044 bytes/sec)
100000000 bytes transferred in 19.656 secs (5087505 bytes/sec)
100000000 bytes transferred in 20.697 secs (4831618 bytes/sec)
100000000 bytes transferred in 20.086 secs (4978592 bytes/sec)
100000000 bytes transferred in 53.975 secs (1852709 bytes/sec)
100000000 bytes transferred in 28.934 secs (3456141 bytes/sec)
Write BandWidth: 3.81448 MBps

Evaluating read-BW...
100000000 bytes transferred in 18.844 secs (5306728 bytes/sec)
100000000 bytes transferred in 17.818 secs (5612302 bytes/sec)
100000000 bytes transferred in 17.331 secs (5770007 bytes/sec)
100000000 bytes transferred in 17.301 secs (5780012 bytes/sec)
100000000 bytes transferred in 17.306 secs (5778342 bytes/sec)
100000000 bytes transferred in 17.310 secs (5777007 bytes/sec)
Read BandWidth: 5.40803 MBps

Cleaning up all the temporary files...

Internal sd-card

$ ./sdCardSpeedTest.sh /mnt/emmc
NOTE: Test might take about 5-10 min depending on your sd-card speed!
      Please be patient during this time...

Evaluating write-BW...
100000000 bytes transferred in 9.372 secs (10670081 bytes/sec)
100000000 bytes transferred in 6.579 secs (15199878 bytes/sec)
100000000 bytes transferred in 6.252 secs (15994881 bytes/sec)
100000000 bytes transferred in 6.321 secs (15820281 bytes/sec)
100000000 bytes transferred in 6.532 secs (15309246 bytes/sec)
100000000 bytes transferred in 6.516 secs (15346838 bytes/sec)
Write BandWidth: 14.0415 MBps

Evaluating read-BW...
100000000 bytes transferred in 5.168 secs (19349845 bytes/sec)
100000000 bytes transferred in 5.038 secs (19849146 bytes/sec)
100000000 bytes transferred in 4.661 secs (21454623 bytes/sec)
100000000 bytes transferred in 4.671 secs (21408691 bytes/sec)
100000000 bytes transferred in 4.694 secs (21303792 bytes/sec)
100000000 bytes transferred in 4.693 secs (21308331 bytes/sec)
Read BandWidth: 19.8165 MBps

Cleaning up all the temporary files...

Phone memory

$ ./sdCardSpeedTest.sh /data/local
NOTE: Test might take about 5-10 min depending on your sd-card speed!
      Please be patient during this time...

Evaluating write-BW...
100000000 bytes transferred in 6.876 secs (14543339 bytes/sec)
100000000 bytes transferred in 8.566 secs (11674060 bytes/sec)
100000000 bytes transferred in 8.565 secs (11675423 bytes/sec)
100000000 bytes transferred in 6.783 secs (14742739 bytes/sec)
100000000 bytes transferred in 7.617 secs (13128528 bytes/sec)
100000000 bytes transferred in 8.168 secs (12242899 bytes/sec)
Write BandWidth: 12.3989 MBps

Evaluating read-BW...
100000000 bytes transferred in 5.537 secs (18060321 bytes/sec)
100000000 bytes transferred in 5.641 secs (17727353 bytes/sec)
100000000 bytes transferred in 5.274 secs (18960940 bytes/sec)
100000000 bytes transferred in 5.275 secs (18957345 bytes/sec)
100000000 bytes transferred in 5.268 secs (18982536 bytes/sec)
100000000 bytes transferred in 5.273 secs (18964536 bytes/sec)
Read BandWidth: 17.7468 MBps

Cleaning up all the temporary files...

I have compiled these results in a tabular format for quick comparison.

Location	Write BW (MBps)	Read BW (MBps)
External sd-card	3.81	5.41
Internal sd-card	14.04	19.82
Phone Memory	12.40	17.75

If you find any issues with this tool, do drop-in a comment here!

How did I 'almost' brick my phone (and recovered from it)?

I use CM7 (nightly-74). When I heard that LG had released 0622 baseband version I couldn't resist to go back to stock ROM and try it out. :) And I did exactly that... However, somehow, during the update using the LG PCsuite, it said 'failed to communicate with phone' and asked me to remove battery, restart and plug in USB and start over again. When I tried that, after the LG boot-splash, I got this screen. :( And that's when I knew, I had screwed up my phone!

Then I went to modaco-forums to find that Paul had given a nice tutorial on how to flash your phone to the stock ROM (using nvflash). I successfully flashed the stock ROM. But little did I knew that worse was waiting when I would boot the phone. My baseband firmware was no more! Meaning my phone had become a wifi-tablet :(( Luckily, I found this thread in modaco-forums on how to flash baseband-firmware (using smartflash). Instructions were pretty simple and using this, at the end, I was able to get back my baseband to 0622 version :D (phewww!!)

Now, I just had to manually install CWM (ClockWorkrecovery Mod) version 4.0.0.5 and restore my CM7 (nightly-64) from the nandroid backups. Now I'm enjoying the nightly-74 on CM7 with the latest baseband firmware!

Manually installing clockworkmod (CWM) recovery on LG O2X

Strange as it seems, on my phone, 'ROM Manager' does not allow an upgrade to the CWM after 3.0.2.8. :( So, I wanted to install it manually. The steps I followed were from the one given by our very own Paul on modaco forums. However, I wanted to understand what exactly those 'install-clockworkmod-windows.bat' kind of scripts did. Here it is... (I used the windows batch file in order to install CWM)

# copy over the psneuter binary to your phone

> adb-windows push psneuter /data/local/psneuter

# give this binary on your phone, the executable permission> adb-windows shell chmod 4755 /data/local/psneuter

# run this exe, (psneuter exploit to gain root access)

# you wouldn't need it if your phone is already rooted(?)

> adb-windows shell /data/local/psneuter

# wait the device to come online (as the above exploit would have killed the adbd)

> adb-windows wait-for-device

# copy the CWM image over to your phone> adb-windows push clockworkmod.img /data/local/
 

# place this image over to the appropriate location?

> adb-windows shell dd if=/data/local/clockworkmod.img of=/dev/block/mmcblk0p7

Clockworkrecoverymod v3.0.2.8 bug! :(

Seems like this version does not properly restore the nandroid backups. I tried to restore using this version and the restore succeeded. However, during the bootup, (LG O2X) it used to hang on the second LG screen! The solution is to upgrade it to later version (latest verion 4.0.0.5) seems to work properly. I'll write a blog on how to manually upgrade CWM sooner...

Android adb “Unable to open sync connection!”

This happens sometimes on eclipse (or you can also experience with working on adb commandline). Unfortunately, the best known solution so far is to:

1. Unplug the USB cable.
2. Disable the USB debugging mode on the phone, and re-enable it.
3. Then re-plug the USB cable!

Courtesy: StackOverflow.

Using LG Optimus 2X under USB debugging mode on Ubuntu

If you want to develop/debug applications or even connect ddms/adb to your LG-O2X, you need to setup udev rules, in order for it to be detected by the OS. I'm assuming here that you have already installed android SDK for this purpose, if not please do so (google it!) before proceeding.

In order to do this, at first you need to open a terminal Applications->Accessories->Terminal. Then type in the following commands into your terminal. As soon as you enter the command below, you might be prompted for your password. Enter it to proceed with privileged access.

    gksudo gedit /etc/udev/rules.d/90-android.rules

In the text editor which opens, enter the following line:

BUS=="usb", SYSFS{idVendor}=="1004", OWNER="<userName>", GROUP="<groupName>"

Where: 

1. <userName> is your user name on this machine. Yes! this means that this setting only works you alone! 

2. <groupName> is the name of the group you belong to on this machine. 

3. 1004 is the vendor ID of LG (Courtesy: theandroidphone) 

4. (Google on how to get your username and groupname if you don't know!)

Save and close this file. Then type the following command on your terminal:

    gksudo service udev restart

After this is done, plug-in the USB cable of your phone (if it's already plugged in, remove and re-plug) and in your phone enable USB debugging by: Settings->Applications->Development->USB debugging.

Then type the following command to make sure your phone is getting detected:

    adb devices
You should see something like below in the terminal:

List of devices attached
XXXXXXXXXXXXXXXX    device

PS: All this information is from my PC running Ubuntu-10.10 (the Maverick Meerkat).

Installing Cyanogenmod7 (Gingerbread build) on LG Optimus 2X

Even though the guidelines to do so are described nicely in the CyanogenMod wiki, there are small things this wiki forgets to mention, which caused me a lot of pain when I followed the steps mentioned in them. This blog is an attempt to make the process of installing cyanogenmod as smooth as possible. These were the steps I followed on my O2X (LG Optimus 2X) to successfully install Cyanogenmod ROM.

Step0. Terminology:
If you are new to the world of android-hacking or new to android, in general, make sure that you are familiar the terminologies mentioned in this wiki.

Step1. Pre-requisites:

Do make sure that you satisfy all these before proceeding!

1. Make sure that you have atleast 50% (to be on safer side, 75% :D) of battery charge remaining. This is highly important! If a low battery shuts down the installation process, then there's a very high chance that you are going to brick your phone!
2.  The Recovery Mode somehow doesn't mount the internal sd-card of your phone. So, you have to make sure that you have another external sd-card plugged-in of atleast 2GB in size (on a safer side).
3. If you have data like contacts, sms, call-log and such other stuffs, now's the time to get a backup of them (onto sd-card). Titanium Backup is a nice app for this purpose. Basically, all of the data on phone will be wiped-clean during this process. So, backup all those things on your phone, which you feel is important to you.
4. You need to download/install all of these tools/files on your PC, before proceeding further: (This tutorial assumes that you are working on a PC with Windows-OS running on it)
1. Install ADB. There's a very nice tutorial on how to install this tool. I recommend you to go through this link for more details. (Please do NOT perform the step4 mentioned the above tutorial link).
2. Download busybox: Download this zip and extract its contents.
3. Download psneuter: Download this zip and extract its contents.
4. Download Superuser apk: Download this apk file onto your PC.
5. LG USB drivers (v3.2.1): Download this exe and install it to your PC.
6. It will be handy if you can extract the contents of all the zip files above into a single directory.
5. Install ROM Manager on your phone: This is a very useful tool in booting to recovery mode and then installing ROM's of your choice.
6. CyanogenMod ROM: Go to this link and download the latest nightly OR if you want to play safe, you can download the nightly numbered 53, because that's the one I downloaded and it works fine for me :). Download it to your pc and then transfer to over to your phone's sdcard. DO remember to store this zip file in the root of your external-sdcard and name it as update.zip!
7. Google Apps: Default cyanogenmod ROMs do not have any google apps installed on them, so you would have to install them by yourself. You can download the zip file from here and then transfer it to the root of your external-sdcard and let's say that you name it as google.zip.

One small thing before you proceed, as soon as you boot into recovery mode, your phone goes into an eternal vibration mode. Don't panic. It's a bug in recovery mode and it will not affect the installation process.

Step2. Rooting:

You need to root the phone prior to installing cyanogenmod. Here are the steps you need to follow for this: (In step4, the commands appearing the first indentation level are the ones you will be typing on the command prompt and the ones in the second indentation level are the ones you will type inside the shell opened by 'adb'.)

1. In your phone, enable 'USB Debugging': Settings->Applications->Development->USB Debugging.
2. Connect your phone to this PC via USB cable.
3. On your PC, open command prompt and 'cd' into the directory where you had extracted all the files from the zip files downloaded.
4. In the command prompt type the the following commands:
1. adb push busybox /data/local/
2. adb push psneuter /data/local/
3. adb push su /data/local/
4. adb shell chmod 777 /data/local/busybox
5. adb shell chmod 777 /data/local/psneuter
6. adb shell
1. /data/local/psneuter
7. adb shell
1. mount -o remount,rw -t ext3 /dev/block/mmcblk0p25 /system
2. mkdir /system/xbin
3. /data/local/busybox cp /data/local/su /system/xbin/su
4. chown 0:0 /system/xbin/su
5. chmod 6755 /system/xbin/su
6. ln -s /system/xbin/su /system/bin/su
7. exit
8. adb push Superuser.apk /system/app/Superuser.apk
5. Reboot.
6. Your phone has been rooted.

Step3. Installing Cyanogenmod:

Note that when you are in recovery mode, you should use the volume up/down buttons to navigate the options on the screen. In order to select an option, press the power button.

1. Open the 'ROM Manager' application on your phone.
2. Tap on 'Flash ClockworkMod Recovery'.
3. Select LG Optimus 2X in the menu that pops up.
4. You will get a 'Superuser Request' prompt. Select 'Remember' and then 'Allow'.
5. As soon as the flash is complete, you'll see a 'Successfully flashed ClockworkMod Recovery!' dialog box. Tap OK.
6. ClockworkMod Recovery should be installed on your phone.
7. Tap on 'Backup Current ROM' in order to backup your current ROM (which is, in most cases, the manufacturer supplied, stock ROM).
8. 'Reboot into Recovery'.
9. Select the option 'Wipe data/factory reset'.
10. Select the option 'Wipe cache partition'.
11. Select the option 'install zip from sdcard' and then select 'apply /sdcard/update.zip'.
12. Select the option 'reboot system now'. 
13. Now, your phone should boot into the Cyanogenmod ROM!

After this, if, you need to install the google-apps using google.zip:

1. Open the 'ROM Manager' and select 'Reboot into Recovery'.
2. Select the option 'install zip from sdcard' and then select 'choose zip from sdcard'.
3. Select the 'google.zip'.
4. Now, after your phone boots up, you'll be taken through series of asking you to confirm what are all the apps you want to be installed. Select the ones you need and you're done!

Lemme know how the info in this blog worked for you! Feedback on whether this content was useful to you would also help. : )

Happy modding!

Java API for Bitly webservice

I wrote a Java API for Bitly webservice (details about this webservice can be found here). It provides a easy interface to the output of the webservice, by parsing the JSON format and storing the values in the corresponding variables inside an appropriate 'BitlyResponse' object. This could be a very useful API for accessing url-shortening services from inside java apps (could be for android as well!). You can find the jar file and the relevant code at the following github repo: git@github.com:teju85/BitlyAPI.git

PS: There's no restriction on the using this library, provided you acknowledge the use of this API in your application. :)

CorrDim: a fast correlation dimension evaluator

After going through this blog written by Bill Maier, I thought why not I give a shot in writing a C++ program to find the correlation dimension and figure out its performance. 'CorrDim' is the result of this. This has some of the most common maps already available within the project folder viz: Logistic map, Tent map and Henon map. Also, adding a map of your choice is a piece of cake, thanks to virtual inheritance. Go through the 'README' file available in the source code to know more on how build and extend this to include more maps. This program supports 2 modes of correlation dimension evaluation:

1. Fast but huge memory: In this mode, the distance matrix will be evaluated apriori so that the subsequent lookups are faster. However, this requires huge memory, especially if the number of elements considered is huge.
2. 'Relatively' fast but consumes little memory: In this mode, the distance matrix will be evaluated on-the-fly, during the evaluation of the correlation dimension, thus requiring very little memory.

The choice of the mode depends on: If you absolutely cannot sacrifice even a little performance, then you should use the normal version. But for all practical purposes, it is recommended that you use the low-memory version.

Profiling:

Here are the results from profiling this program [Results are on a Dell-Latitude E6400, with Ubuntu 10.10 installed and on LogisticMap.]...

Memory Profiling:

Run-time profiling:

As you can see, the LowMemory version of this program gives a significant reduction in memory footprint compared to its counterpart. At the same time, the performance loss is also not that noticeable.

I have hosted this project (open-source'd with GPL) on github at: git@github.com:teju85/CorrDim.git.

Replacing tabs with spaces in eclipse

Tabs are evil! They are interpreted differently by different editors. So, it is always better to setup your editor to replace tabs with a constant number of spaces. IMO, 4 spaces will be visually appealing. While working with eclipse, here's how to set this property: (assuming eclipse version "Helios Service Release 2")

Window -> Preferences -> Java -> Code Style -> Formatter -> New

Give your profile a name, something like 'Eclipse [only-spaces]' and inherit all the basic settings from the 'Eclipse [built-in]' profile. (You can choose to inherit from whichever other profile of your interest or you can directly edit one of your favorite profiles. For me, the built-in profile was sufficient). Also make sure that 'Open the edit dialog now' is checked in and then press 'Ok'.

In the dialog box which opens, select Indentation -> Tab policy -> Spaces only.

Set the 'Indentation size' and 'Tab size' to 4. (meaning 4 spaces, as I mentioned in the beginning).

Press Apply to save all your settings and from here onwards, eclipse will put spaces instead of tabs for the indentation!

The reason I created a new profile is because one can keep re-using this in all your future projects and also has the ability to export your profiles when you want to use this profile on some other machine!