Showing posts with label gadget. Show all posts
Showing posts with label gadget. Show all posts

Saturday, March 16, 2019

Can Raspberry Pi boot from USB flash drive? And about how to do it guide.

Simple answer is 'yes, it can' but read on....
Or skip to the "So I will write summary first:" below.
Or skip to the "Raspberry Pi 3 B+ support USB boot.  How about Pi Zero W? Or other Pi?" below.

Not everyone is beginner, I think.

When people looking for how to guide for installing the OS(operating system), they were probably beginner or very first time trying to use Raspberry Pi. If that's the case, step by step guide might be very good choice.

But even so, it is better to explain general concept, I think.

If someone already knew some computer stuff, he or she probably doesn't need that step by step guide. Because Raspberry Pi is computer that means it is same concept.
For example, someone is Windows user like me and some Windows user knew if computer--motherboard support USB booting, Windows user can simply go to the CMOS setting and do boot from the USB stick.
So I'm thinking Raspberry Pi is computer so it might support USB boot, too.

So I'd like to know whether Raspberry Pi support USB boot or not. Or I might have to do something to get USB boot.
That's what I want to know, right?

So I will write summary first:

BCM2837-based Raspberry Pis which were all the Pi 3 models include compute module 3 and Pi 2 Model B v1.2, support USB host and Ethernet boot.

So if you have any of models with BCM2837, you can follow any general install OS guide (and install to the USB flash memory stick) which you might already knew.

And if you have other models include Pi Zero and Zero W, you need single file on your micro sd card and then it will boot from USB memory stick. So you can boot from USB memory stick and also need micro sd card with single file which I will explain below.

thought about boot from SD and then USB.

I am currently using the multiboot via berryboot.

And sometimes, I felt berryboot wasn't enough what I am trying to do. So I am thinking about like that.
3 or 4 OS on SD card and then 1 or 2 OS from USB flash memory.

So I was googling about it like this:
how do i install raspbian on usb memory

And I clicked below guide:

And read this part:
Important information
This tutorial is out-dated and has been updated here: ....
So I did clicked link which is below guide:

I have a Linux machine but most of my data--Raspberry Pi image file and etc, was on Windows which is my main computer.
So I clicked Windows version tutorial--below link.

I appreciate the detail guides. But when I am trying go through this guide it made me very confusing.
See this "Step 2 – Install Raspbian to the micro sd card"
And then "Note: If you’re using a Raspberry Pi 3+, you don’t need to do step 2. Jump straight to step 3."

"Step 3 – Install Raspbian to the USB Flash Drive"
The process is exactly the same as step 2, but this time we choose the USB flash drive as.....

And here--"If you're using a Raspberry Pi 3 Model B+, you can skip step 4."

"Step 4 – Prepare the Raspberry Pi for boot from USB"

"Step 5 – Boot Raspbian from USB Flash Drive"

I realised that it is exactly same step as install Raspbian on micro sd card.

I have Raspberry Pi 3 B+ and Pi Zero W. So I already knew how to installing any OS on micro sd card.

As you can see, it took very long time to figure out.
Unfortunately, I clicked very old guide--May 2013. That probably is the reason though.

Raspberry Pi 3 B+ support USB boot. How about Pi Zero W? Or other Pi?

I am thinking newer Pi can support boot from USB memory stick but how about Raspberry Pi Zero W which I also have.

So I googling about it and found this:

This question already reveal how to do the booting from USB stick.

Quoted from the question.
The older Raspberry Pi's (Pi 1, Pi 2 and Pi Zero) couldn't boot from a USB-device, but the Raspberry Pi 3 has support for it. The Pi and Pi 2 have semi-support for it (using an SD-card with a single bootfile).

So if I wanted to boot from USB stick in Pi 1 and 2, I can place single bootfile--which I don't know it yet.

And other people answered that Pi Zero W use older chip like Pi 1 and 2.

And then I found someone wrote about that single bootfile--bootcode.bin.
And pointed to the source:
Special bootcode.bin-only boot mode section in Raspberry Pi boot modes - raspberrypi/documentation
Quoted from above link:
USB host and Ethernet boot can be performed by BCM2837-based Raspberry Pis (these are all Pi 3 models, and some Pi 2Bs). In addition, all Raspberry Pi models can use a new bootcode.bin-only method to enable USB host and Ethernet booting.

Just format an SD card as FAT32 and copy on the latest bootcode.bin.

This is useful for the Raspberry Pi 1, 2, and Zero models, which are based on the BCM2835 and BCM2836 devices, and in situations where a Pi 3 fails to boot (the latest bootcode.bin includes additional bugfixes for the Pi 3, compared to the boot code burned into the BCM2837).

If you have a problem with a mass storage device still not working even with this bootcode.bin, then please add a new file 'timeout' to the SD card. This should extend the time it waits for the mass storage device to initialise to six seconds.

I'm not 100% for sure yet. But if Raspberry Pi use BCM2837, USB host and Ethernet boot will support.

And I found all the Raspberry Pi specifications from Raspberry Pi - Wikipedia.
Screenshot of Wikipedia's Raspberry Pi Specifications section.
And as you can see, Pi 2 Model B v1.2 uses BCM2837. And all the Pi 3--3 Model A+, 3 Model B, B+ and Compute Model 3, lite, 3+.

So if you have Pi 2 Model B with v1.2, Pi 3 series and Compute Model 3 series, you can just install any OS on USB stick and remove micro SD card.

If you have other version include Pi Zero W, you can format the micro SD card and copy the bootcode.bin file.

Yes, I haven't tried it yet. But I think those are from the Raspberry Pi's official repository.
So I'm sure it will work.

Kali and Raspbian booted from USB flash drive.

I probably have to get more information about it so I just found this:
quoted from above link:
HawaiianPi wrote:
The Pi3 will check for a boot SD card first, before booting from a USB device. If no boot SD card is found in 5 seconds, then it looks for a boot USB device.

I think this is quite similar process as USB boot in PC--desktop and laptop computer.

When I read from above link, someone said some USB disk won't work. And I wasn't sure about it--If it's FAT32, why it shouldn't be.

But first I tried with quite old 8GB USB stick, it didn't work--Pi 3 B+ without micro SD card and Pi Zero W with single file on micro SD card.
So I thought I need to do something.

And I realised this could be compatibility issue. So I put my kind of new memory card read which can read SDXC format card, too.


As you can see that micro sd card slot is empty.
Kali lite booted from USB Flash memory stick in Raspberry Pi 3 B+.
That USB memory stick doesn't work with USB boot--I tried like 2+ os and also with Pi Zero W.

This time, I tried same USB memory card reader with Pi Zero W. And it worked well.
And I had to put single file in micro sd card.
Raspbian stretch booted from USB Flash memory stick in Raspberry Pi Zero W.

If you'd like to connect more than two USB stick, portable hard disk or SSD, things became quite complicated. Because Raspberry Pi doesn't know which USB drive to boot from.

So you have to search more about it.

I hope you did learn about the basic concept or process of USB boot in Raspberry Pi.

Friday, March 15, 2019

Adafruit's Portable 5 inch Monitor with HDMI DIY looked interesting. But in reality....

I've seen this video: Portable HDMI Display for Raspberry Pi - YouTube

And I thought it looks very nice and quite useful because it isn't only for the Raspberry Pi--I can use as my DSLR monitor or game console monitor as well--I have a Nintendo NES classic edition which is kind of portable console.
So I'd like to do this....

It's expensive than I expected.

But when I saw inside of it, it shouldn't be easy to do.
Building the portable monitor won't be easy, for sure--I haven't done soldering before. But it requires a lot of parts to buy, too.

And if I do this, I might learn a lot of things about Adafruit, for sure.

So I visited building guide wep page.
Overview | Portable 5in Monitor with HDMI | Adafruit Learning System

And I realised I don't only spend a lot of time, I need a lot of money to building it, too.

  • 5.0" 800x480 TFT Display $29.95
  • TFP401 HDMI Breakout $24.95
  • FPC Extension Board $4.50
  • Powerboost 1000C $19.95
  • 2500mAh Battery $14.95
  • Slide Switch $0.95
  • Tripod Screw Insert $1.50
  • Total: $96.75

I thought this is too expensive for me. I need other things like print 3D case and lots of tools to do this.

So when I go through their guide, I saw that it can powering up the screen through USB.
That means, I can simply use my smartphone powerbank.
So no need to buy Powerboost 1000C and 2500mAh Battery.
And I don't have 3D printer so I don't need slide switch and tripod screw insert, too.

So I need three parts--5 inch display, TFP401 HDMI breakout, FPC extension board.
So total $59.4.

Cheaper or even better alternative--Aliexpress.

That means I don't need to do this.
Because I can simply buy from cheap Chinese store in Aliexpress, like this:
This is screenshot of 5 inch capacitive lcd display from Livetime Store in Aliexpress.
5 inch Raspberry Pi 3 Model B+ Touch Screen 800*480 Capacitive LCD Display + HDMI Cable + USB Cable + CD for Raspberry Pi 3-in Demo Board Accessories on

This is 5 inch capacitive touch display. And it costs $38--include free international shipping.
This model was different driver board design than 5 inch resistive display so I couldn't find case for this model.
5 inch resistive display case costs $6 to $10 in Aliexpress.
I can buy 5 inch display with case for about $48.

So it's much cheaper and better(include touch panel) than Adafruit's.
I know this because I just ordered one from there. So I search the a lot of similar--5 inch lcd.

If I wanted to learn about Adafruit, I probably can invest that much time and money.
But now I'd like to more focus on Raspberry Pi--and programming.

So I will buy 5 inch capacitive touch display.

You can also buy other 5 inch screen from Aliexpress like this:

This is the screenshot of '5 inch lcd hdmi' search result in Aliexpress.
Buy 5 inch lcd hdmi and get free shipping on

This is the screenshot of '5 inch screen' search result in Aliexpress.
Buy 5 inch display and get free shipping on

When you are searching the lcd screen, it doesn't show up many items. But you can find store that specialize in Raspberry Pi or SBC(single board computer). So you probably have to check Raspberry Pi store one by one.

It looks hard to build but maybe not that much.

At first, I don't think it's easy thing to do. When I saw this link:
On/Off Switch | Portable 5in Monitor with HDMI | Adafruit Learning System
It doesn't seem to easy, does it?
But if you are thinking about portable project, I think it's worth the effort.

I saw the next page. And if I learn about soldering, I think I can do this.
TFP401 Driver | Portable 5in Monitor with HDMI | Adafruit Learning System

And next,
Display | Portable 5in Monitor with HDMI | Adafruit Learning System
This part need just connect and position the cable. After that, screen is working.

Next part is mounting to the case.

Overall, if I learn and practicing soldering, it shouldn't be so hard.

But I still don't have a 3D printer and I don't like spend that much money.
So I will buy from Aliexpress.

Many of web store like adafruit, elements14, sparkfun, pimoroni were probably based on USA or UK so shipping and currency is too expensive to my country--Korea.
And same kind of store in Korea was all imported from those countries so things were much more expensive.

That's why Aliexpress is the best choice--for me. And probably to you, too.

Monday, December 17, 2018

How the sixty dollar console-Nintendo classic mini, costing an arm and a leg?

Summary – Sad story of a sixty dollar console costing an arm and a leg.
quoted from one of Amazon user's Nintendo NES Classic Edition Console review:

I also found similar one from customer Q&A sections @ #Amazon's Super NES Classic item page
Q: Will we ever have a chance to buy this?...
A: willing to pay but when you make it impossible to get except rip-off-bay it makes it meaningless that....

Simply put - Nintendo didn't make enough products and they just kept trying to shutdown the productions because they wanted sell their other main line product like Nintendo Switch.

Here is evidence of what I said was probably true:
Despite the positive reception, journalists were confused about Nintendo's decision to discontinue the unit as announced in April 2017. Nintendo did not say at launch that the system was meant to be only a limited run, and its...
quoted from Reception section of NES Classic Edition - Wikipedia

Their products are selling so well but they were simply stop producing the product. Does it make sense to you?

NES Classic Edition

Nintendo NES Classic immediately sold out

The NES Classic immediately sold out when it was first released in November 2016, with resellers charging hundreds of dollars for the popular product.
quoted from Nintendo's NES Classic and SNES Classic are going out of production - The Verge

more details from Scalping and bootlegs section of NES Classic Edition - Wikipedia
This, coupled with the extremely high demand, prompted internet scalpers to buy as many as they could, so they could resell them with extreme price markups. In the US, prices were commonly set between $200 and $500, compared to its launch price of $59.99.

Sunday, June 17, 2018

answer--not physically destroy hdd, for erase data from a hard disk so no one can ever recover it.

Thinking about selling used hard drives.

Recently I bought external 2.5" hard disk drive because my external 2.5" hard drivers have low on free space. Copied all the data to new hard drive from old hard drives.
Now I have number of hard drivers--external 2.5" 500GB, 750GB and a few desktop PC 3.5" hard disks that no use. So I'm thinking about to sell it.

Before I'm selling, I needed to clean up the hard disk so no one can recover my personal data. I don't much have important data though--I have a lot of piece of writings and ideas. But I don't think people will understand what those a pieces of writing is for.
I know this because some of those ideas, I already wrote in my twitter or blogs but no one seems to understand what I am saying. So I don't much care about those.
But I have been learning photography so I have tons of photos which I'd like to erase it.

So I did googling and came across this--in Quora:
How do I erase data from a hard disk so no one can ever recover it? 

Why would you like to physically destroy hard disk which you spend a lot of money for?

Quite surprise to see so many answered with physically destroy the hard drive.

I thought -
Nowadays, everyone is sooo rich that everyone suggest to physically drilling, shredding the hard disk.
I'm not rich so I had to completely erase the data before selling.

I know the simple solution without physically destroying it.

I know how software works--because I was a programmer. So I know very easy and simple way. Download some software--bigger size will be better, useless documents or anything from the internet or your not important things like Netflix movie files. And delete all your data. And then copy the downloaded software, documents and all. And kept copy it(same files over and over--make folder to more easier--Windows will make new name for it like below screenshot) until hard disk became zero-ish byte of free space.
screenshot: overwrite files for make unrecoverable

So when the recovery software or professional try to store data from my hard drive, they will only recover those useless data.
It's THAT simple to permanently erase data.
Yes, it takes time. But it perfectly works.

Yes, someone answered what I suggested--overwrite data to remove personal data.
And someone saying that forensic analyse(or something) still can find a bit of information from there. Sure. That might be true.

That's why my solution makes more sense.

Because my personal data was already replaced by thousands, thousands and thousands of files.
That means forensic analyse take more, more and more time to figure out which bit of information connected to the which part of information. It's like thousands, thousands and thousands of jigsaw puzzles to figure out.
And it will be almost impossible because a lot of pieces were missing.

Loren Forslund answered very interesting one and I think it's very good method, too:
My method is using Ubuntu disks utility to break all partitions down and formatting the drive into one “FAT” partition. Now make 2 equal partitions and format them in EXT4 writing over the drive. Now break these partitions back to one NTFS partition over writing the disk. I’m sure if you had one million dollars worth of DOD equipment and 3 months of time you may get a scrap of something, but I doubt anything useful.

People watched way too much TV shows--CSI kind of TV shows.

Especially this part:
I'm sure if you had one million dollars worth of DOD equipment and 3 months of time you may get a scrap of something, but I doubt anything useful.
 - People were watched way too much TV shows
 - and they were way too much talk about this theoretical ideas.

Let's talk about reality.
I told you that I bought a external 2.5" hard disk which has 4TB space--actual size is 3.63TB.
So I put all my old data to this new hard disk..
screenshot: my external hard disk drive's files and folders

Last time, I had a lot of software and documents from the internet. But when I started taking photos, I had to delete those files because nowadays DSLR or mirrorless camera need bigger space to backup.
And other reason is I can always go online to get those software again.  So I don't need to kept in my hard drive.

So in my case, 50% of files(153,598 / 2 = 76,799 files) were probably personal data. But each photo was like 7 to 24 mega bytes only. I have software, downloaded documents, audiobook from Librivox and games and those were far more bigger size than photos.

So even if I have 50 to 70% of files were personal data(because photos I took), 40 to 80% of space were filled with not personal data. That means 40 to 80% of 0.98 tera byte.

That means if forensic analyse find a bit of information, it will quite likely not my personal data. For example, 70% of space were not personal data means:
other not important things - 1,003.52 giga byte * 70% = 702.464 giga byte
my personal data - 1,003.52 giga byte * 30% = 301.056 giga byte
Because my personal data was only 30% chance to picked up by forensic analyse.

And there has more. I have thousands of photos but do you think all of my photos were all very important photos--which I probably use it in my blog.
Photography is my hobby so technically it wasn't very important data.

Even if so, reality is this:
How many professional photographers really use all of their photos they took, do you think?

And how many people do you think they use their hard drive only for their important data?
Even if that's the case, why do they need 1 to 4 tera bytes of hard disk?

I have important documents but most of my documents(which I kept it in text file format--smaller than Word file format.) takes only a few kilo byte.
So I'm sure that a few giga bytes of hard disk should be enough for their personal--important data.

Reality of un-delete kind of software.

How I know this? Because about 10 or 15 years ago, I tried to recover my important data from un-delete kind of software with no success.
I can see the files with so many other files. But I can't recover it because it was already half destroyed--some new files already overwritten some part of those files.

You've known this, too. Good example is 'corrupted file'. Did you recover that corrupted file?

Reality is this:
Even if that forensic analyse find a bit of byte, what can you do with that part of byte?

It was 10 or 15 years ago experience so I have to check. And found this:
Recovering Deleted Files After Formatting: Is it Possible? | Deleted File RecoveryThere are many debates regarding the possibilities of recovering deleted files among computer scientists. All evidence points to the fact that in order to recover files deleted from recycle bin, or any other part of the operating system, they must not have been written over.

In order to recover a deleted file every sector that included data for that file must be in it’s original condition. Overwriting any part of this file with new data will cause corruption.

As you can see, this professional(??) data recovery company saying things were far different than what many people answered in Quora.
Professional data recovery company saying that they can't recover if it's already written over.
But many people in Quora saying that you can recover it--because you can find a piece of information with forensic analyse(or something). So you must do physically destroy hard drive--drilling, shredding, burning and among other physical way.

See the difference.

Even if you recover the part of file, you probably can't read--because of corrupted. But what many people in Quora saying is it can read--recover it.
* If you seen CSI kind of TV show, they can always recover it, don't they?
Yes, you can recover the random data. But do you think that random data is worth a million dollars with spent a few months or a year of work?

That's why I completely agree with what Loren Forslund said:
I'm sure if you had one million dollars worth of DOD equipment and 3 months of time you may get a scrap of something, but I doubt anything useful.

Reality is extremely different than what people were saying in internet, unfortunately.
This is how people kept getting more wrong ideas.

P.S. I found permanent file delete software:
They also explain same thing--overwrite to make unrecoverable.

Wednesday, March 29, 2017

This is the reality---how Apple fanboy dominated this world. - Reality of web storage service.

I've got photos from friend--

screenshot from Best Of Quora facebook page

I didn't even read whole thing because I know the cost of web storage.

So I wrote in my facebook timeline:
This is the reality---how Apple fanboy dominated this world.
Do you know how much does it cost for 5giga byte storage for internet?
Do you know even give you free for about 200 times more size--1 tera byte of hard disk? Of course, they will display the advertisement but it was soo small that you will not even notice it.
Are you living in stone age that you think 5 giga byte of storage were some kind of miracle size?
Go and learn how internet became nowadays.

It wasn't really unlimited storage. And it wasn't started like that.

I was quite strange that Google give unlimited storage because there has limit. What I know is it will reduce the size, that's why I've got only 15 giga byte which isn't free at first, if I'm not mistaken.

Google advertised when you buy the android phone, you will get 15 giga byte of web storage.
I thought that 15 giga byte of web storage was really big about 3 to 5(??) years ago. But actually it wasn't.
Because I'm sharing with all of my google services like email, google docs, drives, photos, videos and even here--my blog service.

See. Actually it wasn't big. Because each product has 3 to 5 giga byte which is almost same as any other service.
For example, wordpress which is same as blogger here, give 3 giga byte of storage. You can read details here-Adding Storage Space — Support —
Other example, dropbox which is same as google drive, give 2 giga byte of storage. You can read details here-How much does Dropbox cost? - Dropbox Help - Dropbox
Onedrive which is same as google drive, give 5 giga byte of storage. You can read details here-Microsoft OneDrive Plans

People--even internet technology news writer, actually don't know why google give 15 giga byte. And they think google gave it for free because it was big.

Some of us know 15 giga byte was actually not big. So does Google.

Unlimited storage but compressed image--that means image quality will loss.

So Google offer the unlimited storage with limited photo size. I probably confused about this but if I'm not mistaken, they reduce the size more than half size if it was even 13 mega pixel. That's why I choose upload photos with original quality. I choose that almost year ago, I think.

Google Photos: Unlimited storage for free, with a few gotchas @ June 1, 2015 By Todd Ogasawara
Google Photo gives you unlimited storage space if you are willing to limit photo resolution to 16 megapixels and video resolution to 1080p. You do have the option to store at higher resolutions, but the storage counts against your Google Drive quota.

But it's not only photo resolution. It will compressed image, too.

Choose the upload size of your photos and videos - Google Photos Help
Photos are compressed to save space. If a photo is larger than 16MP, it will be resized to 16MP.

Or if you can buy a Google Pixel phone, you will get unlimited storage without those limitation. You can read here - Google is giving free, unlimited original-quality photo and video backups with the Pixel phones @ Oct 4, 2016 by Lauren Goode

Wait a sec. So Google only offer that much!?

Facebook, almost everyone using nowadays, right?
I've never seen any limitation of photos. People kept uploading it, don't they?
Yes, reduced photo quality(like Google does or more) and size but they gave almost(??) unlimited size, don't they?

How about Instagram?
Do I heard any limitation about photo uploading?
Yes, reduced photo quality(it wasn't much, I think. More for the size, I guess) and size. But they gave almost(??) unlimited storage, don't they?

How about which I mentioned very earlier.
Yes, they offer 1 tera byte of storage.

Do you think do I have to find out all the other websites about the offer? It's enough, right?

See the title of this article. "This is the reality--how Apple fanboy dominated this world."
That's why who has best answer. And choose that--Apple fanatic side of story, for the best of quora.

P.S. Slightly different but almost same story - Illogical idea ruled internet--especially social networking sites. @ March 17, 2017 - my other blog.

P.S. (at April 3, 2019): I found this question at - Why does Google offer unlimited storage for photos via Google Photos app? What's in it for Google?
So many answers include what I mentioned here.
Interesting thing is nobody talked about facebook or instagram. Because I'm sure they know about the websites and very likely using the websites. But they don't even know facebook and instagram gave unlimited photo storage like Google does--I'm sure some of their friends uploaded thousands and thousands of photos.

Wednesday, May 25, 2016

Nexus 7 2013 Marshmallow, won't allow to install app--apk file.

If you are looking for solution in forums, they will probably ask 'why you need install app without Google play store' or 'are you trying to install cracked app--illegally unlocked copyright version app'.

I tell you why I need this.
I bought secondhand Nexus 7 2013 (second generation) tablet for my sister so I don't want to do all the things like google log-in process and wasting my limited internet resources (I don't have unlimited internet access.) for downloading apps and sync the app data,
for just testing the tablet.

I just wanted to install some apps like movie play app, photo viewer app, music player app, camera app and some 3d-ish game app or copy some video file so I can check whether this secondhand tablet will work properly or not.

So I just need to install two to four apps to testing the tablet.

Here is the tablet's version info:
Nexus 7 and Android 6.0.1
Screenshot of Settings -> About tablet in Nexus 7

check 'Unknown Sources' in settings for install apk files

If you searched web for 'how to install app (apk file) in Nexus 7', you will find solution like this
Settings -> Security -> turn on 'Unknown sources'
Screenshot of Settings -> Security in Nexus 7

but this doesn't work. Because tablet still don't allow to installing the app.

Screenshot of Settings -> Storage -> Internal Storage
Screenshot of Settings -> Storage in Nexus 7

'Explore' to install the apk file.
But you will get message like this:
'Cannot open file'.
When you trying to install the apk file, you will get error message like this.

How to transfer apk file in Nexus 7.

Many of Android smartphone and tablet probably will have MicroSD memory card slot so most cases you can copy files easily. And not only that.
They will probably have USB-OTG function which you can simply put the usb memory card to the smartphone or tablet via USB-OTG cable.

But Nexus 7 don't have memory card slot. So what you can do is send file via bluetooth or NFC. Or use internet or connect PC with usb cable.

But it looked like apk file won't allow to do transfer via bluetooth or NFC. So you can do it via internet or connect PC with usb cable.

So I use send-anywhere websites to transfer apk file:
trying to send file via

and then use download app to install apk file but I've got same error 'Cannot open file'.
'Downloads' app to install apk file but same error - can't open file

I can transfer to the apk file but can't install it.

Only way to install the app is use android app development tool ADB.

I already install the Android Development Tool on my PC and this article became quite long so I will not explain how to get and use the tool.

You can follow one of these articles:

You don't need install whole Android Development Tool to get ADB file. You can find only ADB file and Android USB Driver for Windows(or possibly your system already have it).

You need to turn on 'USB debugging' option in 'Developer Options'. That means it must turn on 'Developer Options' via clicking 7 times in Settings -> About tablet -> Build Number.
* detail guide is here How to enable developer settings on Android 4.2 | Android Central

Connect tablet to PC and then Window+R to type 'cmd' to enter 'Command Prompt' console mode.
install apk file in Nexus 7 via ADB tools - Windows

Make things easier, copy the apk file in the same directory as ADB file is in, and change apk filename short like this because Windows Command Prompt won't easy to handle long filename.
For example here is 'adb install es.apk'.

Finally, install the apk file via ADB from PC.

So it should better install File Explorer app like ES File Explorer. Because this app will allow to install apk file like this:

install app from ES File Explorer in Nexus 7

install app from ES File Explorer in Nexus 7

installed app from ES File Explorer in Nexus 7

If you need more detail guide about use ADB, you can do similar like this: [GUIDE] How to install APK Files on your Nexus Player | xda-developers forum
This guide is for Nexus Player but most of Android smartphone and tablets were all the same.

P.S. I'm quite confusing because I did this many times with variety of Android smartphone and tablet. But many times, I just sent apk file via bluetooth and installed easily with turn on 'Unknown sources'. Not like this.
So this is probably Marshmallow problem. Or Google probably blocked 'Unknown sources' option.

Tuesday, May 24, 2016

How to switch or select OS(operating system) in Teclast X98 dual boot tablet.

I bought secondhand Teclast X98 Air ii and I couldn't find any way to enter Windows OS(operating system).

So I googled it and I found that

to enter OS selection screen in Teclast dual boot tablet.
'Volume Up' button + 'Power' button will enter the OS selection screen.

How to switch or select OS(Operating System) in Teclast dual boot tablet.

Easy way to do this is first press 'volume up' button and then press 'Power' button.

How about other dual boot tablet?

Many other tablets like Chuwi, Cube has dedicated Windows application and Android system app so you can use this application or app to change to desired OS.

And Teclast X98 Air 3G also had this app. But Teclast X98 Air ii doesn't have this app--maybe there has but my tablet doesn't have.

If you have Teclast X98 Air 3G and would like to install os-switch app, you can check this link:

Details about OS selection process in Teclast dual boot tablet.

When you enter the OS selection screen,
Teclast X98 Air ii - OS selection (Android, Windows) screen

you can either choose from top left corner check-box:
  • boot up OS without OS selection screen
  • or boot up OS with OS selection screen in 10 seconds.

Teclast X98 Air ii dualboot tablet- OS selection (Android, Windows) screen explained

So if you remove that tick in check-box, you won't see this OS selection screen. So if you need to change OS, you have to Volume Up and Power button together to see this screen.

And choose whatever OS (Android or Windows) you desire, and touch 'choose OS' button.

When you changed OS, you will see message like this:
Teclast X98 Air ii - when the os selection was changed.

Thursday, May 19, 2016

Teclast X98 Air ii, dual boot tablet - how to change memory size for android.

Is it possible without reinstalling the system?

Answer looks like 'no' at the moment.

I am trying to reduce the Android memory size and increase the Windows hard disk size.
What I have found so far, I can delete whole Android system or delete whole Windows system.
It looks like quite hard(or impossible) to reduce the Android size because Android uses 7+ partition which you can see the below photo.

So it should better to install one by one--Windows 8.1 and then Android. Or vice versa. During installation, I think it can allocate partition size--I haven't found out yet so it was just my guessing.

First, how much space on the 64GB hard drive is assigned to Android and Windows?

I bought secondhand x98 air ii 64gb so I'm not sure about whether it is factory setup or not.
But mine was 39gb(include 5gb for windows recovery) for Windows and other remains--22gb(it seems) for Android.

Here is partition allocation table from Windows' disk management.
Teclast X98 Air ii 64gb - default partition allocation - Windows 8.1's disk management

Here is Android's memory size from storage menu in settings.
Teclast X98 Air ii 64gb - default Android memory size - Storage menu in Settings.

Second, what is the optimal partition size for Android and Windows?

I think there hasn't any optimal partition size because it's all depend on usage.
I don't like installing so many apps on Android and Windows. So in my case, 8gb is surely enough for my Android--I have a 16gb android tablet and half was empty so I can manage with that size. And I can put data(ebooks, songs, videos, etc) on micro-sd memory.
And I don't need big memory on Windows but sometimes, some software need big size--mostly games, so I'd like to have more space on Windows.

I'm thinking about upgrade to Android 5.0 from 4.4.4. So during that process, I hope to reduce the partition size.

This is one guide that delete Android and then those Android's memory allocate to Windows so without reinstalling the os--operating system.

* Koko Pudja's guide: How to delete Android and merge partitions in Windows for more space
Same tutorial but with photos to help much easy to follow.

I think this guide is apply to all the dual boot tablet such as Chuwi, Teclast, (Onda, Cube?) which had two operating system, Windows and Android.

Thursday, October 2, 2014

You are glad to limit your imagination!?

You shouldn't limit your imagination. But you are happy to limit your imagination to 3.5 to 10 inch iPhone, smartphone or tabletPC screen.

Wednesday, May 28, 2014 will shutdown.

This is what I wrote to my twitter account.

#Springpad Interesting idea and it could better. But painful to use & horribly slow. Managing the text is that hard?!

If you'd like to know what I mean, you can simply install #Ted text editor in #playstore. And then run it. & run the #Springpad. compare it.

They had some interesting ideas and it went well.

But they took same mistake path like poor performance in fundamentally important thing. However you try to change, is basically text editor. So if it lose competency in fundamental thing, people won't try to use it much.

It means company will lose their customers.

Saturday, January 25, 2014

Many gadget lovers are living in their own small world.

What a ridiculous idea. If I'm not doing in wedding photography, I am not a professional photographer?

Get out of your narrow-minded world.
He or she was talking like looking down photographers who don't use mention the product. People use product their needs, not by your choice.

No wonder there has movie call the 'The Matrix'.

Friday, September 27, 2013

I don't want to lose all my data when Android phone's pattern was locked with no internet connection.

I didn't use this phone for a while so I have forgotten the pattern. So I was trying to remember it but failed several times.
And I've got this message.
'Too many pattern attempts' in Android phone. Because I totally forgot the pattern.
'Too many pattern attempts' in Android phone. Because I totally forgot the pattern.

And I googled it and I found the way but I turned off the internet so I can't unlock it with my google account.

So I googled it again and I found the way which requires factory reset. But problem is factory reset means erase all my data which I don't like to do.

No internet connection. I can't turn wifi on when Android gadget's pattern was locked.

And finally I found the way that doesn't need to factory reset.

Here is the article:

Unlock an Android Device without Internet Access – Using ADB commands @ February 28, 2013 by chethakau

Here is what I tweeted about it:

#Unlock an #Android Device without Internet Access – Using #ADB commands by chethakau
5:58 PM – 23 Sep 13
I can do factory reset but don't want to lose all my data. Problem is phone's wifi was off and without sim card so no internet connection.
6:18 PM – 23 Sep 13

There has some requirements for to do these steps so you should read that article before do it.

Anyway, now I can use my phone again so thank you, chethakau.

P.S. My previous blog is in wordpress but I have to move to here. So I'm sorry about the confusion.

Wednesday, September 25, 2013

Why Google Chromebook doesn't much attract?

I am using the catch website which can keep personal memos and notes. Mostly, I am using this app from Android phone.

And I just thought that this app might have Chrome browser's app so I can make notes without internet connection, I thought.

This is a screen shot of catch app in Google Chrome's webstore.

What this app does is just open the website of catch. Nothing more.

So this is an app or just a bookmark?

I know some people might need bookmark as app but if Chromebook can't use with internet connection, how can you sell the product to the country with not-so-good internet connection and people who living in outside city-I don't think most country has very good internet infrastructure in countryside.

Oh, I forgot to mention that not only catch app did this.

I have seen a number of apps did this, too. And even google apps.

Anyway, that's why I wrote review with this comment:
Nowadays, bookmark became app. How clever!

Thursday, May 12, 2011

How that place was beautiful? I can't see it.

It could be sarcasm but I don't see how that place was beautiful.

Mobypicture user Ancilla Tilia uploaded photo with this: Our shooting location Oudewater is so beautiful!

I can imagine that house looked pretty but I have absolutely no idea how beautiful that was. Because I've never been there.

Because it doesn't have any natural and real color in it.

So I had to googling about it: oudewater – google image.

And I found this photo which was almost same site: Havenstraat, Oudewater by JohanBakker

I couldn't know why is beautiful until I found a real photo of place
* This old link doesn't work but you can simply find wikipedia's photo from here.

Can't you see the problem with iPhone?

Friday, April 22, 2011

That's why Nokia was far more useful than iPhone.

I saw a photo from
Here is the one:

photo taken from Rick Bayless’s mobypicture

It doesn't look that nice. I mean I don't think I will go to eat that one. Because it doesn't look tasty.

That photo uploaded from Twittelator Pro – iPhone App so it probably taken with iPhone.

So here is mine that taken with Nokia 5800 XpressMusic.

It was side dish for drinking beer.
But I am sure that this one looks tastier than above one.

I didn't edit anything from that photo. Because I don't even know how to use Photoshop program.

If you want to showing the photo about your work, I really would suggest to use Nokia phone.

Friday, April 15, 2011

Cherry blossom in Sinchungyo, Daegu – comparison shot for Nokia N97 mini vs. Motorola Milestone

Nokia N97 mini has 5 Megapixel with Carl Zeiss optics and autofocus and dual LED flash.
Milestone has 5 Megapixel with autofocus and dual LED flash.
So Carl Zeiss optics was only different thing.
But you can so easily find the differences from the photo.

It was late afternoon so Milestone probably couldn’t get the enough light.

Cherry blossom in Sinchungyo, Daegu by Nokia N97 mini

Cherry blossom in Sinchungyo, Daegu by Motorola Milestone

Cherry blossom in Sinchungyo, Daegu by Nokia N97 mini

Cherry blossom in Sinchungyo, Daegu by Motorola Milestone

Tuesday, October 12, 2010

What Nokia N8's video recording makes so special?

I have written many things in my Korean blog and then I thought about doing the video podcasting.
But I didn't have video camera so I have search for the advice from the web.

Microphone U87
Image via Wikipedia

Importance of audio

Here is what I found:

Selecting The Right Video Camera For Your Video Podcast @ October 28, 2006 By Scott Bourne
No matter how good your camera is, no matter how pretty you are, no matter how great your script, it's the audio that will make or break your video podcast.

Quite surprising, isn't it?'s Chamunks @ May 5, 2007 ask the question about video camera for podcast and jpmack answered it with importance of audio.
Here is what he said:
For video podcasting, video quality is not a big issue, audio is.

MacMost Now 121: Video Podcasting Secrets by Gary Rosenzweig @ August 15, 2008 He makes a few suggestions and one of them is "Use a good mic".
And Daniel commented in this article that
Get a Good MiCROPHONE! Even the coolest shows can be hard to hear sometimes.

But not many people recognized that audio is important. Becuase if people knew about this, people must know about benefit of Nokia N8's two mics.

People tend to believe rapid improvement on technology so these old findings weren't that important.
And not many people are doing the video podcast so people don't think it was really important.

But professional podcaster or cameraman must know this. That's why I found that kind of findings from the web.

One of my secret ingredient for speech.

Whenever I gave a speech for group of people, one of thing that help me to succeed speech is a very loud voice. So the audience can hear clearly what I am saying.
I know there has many other factors, too.

Let's think about it this way. If you gave very good speech but some of the people in group couldn't hear what you were saying, it was pointless, wasn't it?

So when I gave speech, I was trying to raise my voice. But recording the video will decrease volume of my voice and then I can get just acceptable volume in youtube video.

Here is link of my youtube video. It was Korean language. But you can still hear the volume of my voice.

Nokia N8's two mics make so different than any other.

Here is video from BesteProduct.

Nokia N8 vs iPhone 4 video test

I am not going to talk about here for video quality because 720p HD video was quite good enough for web video or casual use.

But you can certainly notice the audio. Nokia N8 have front and back microphone so it really helped what people were saying in the video. (It wasn't English so I couldn't understand though.)

Jay Montano also said
Compared to Nokia N8, iPhone 4 audio recording is absolutely PANTS.

about this video in Video: Split Screen Nokia N8 versus iPhone 4 video (and audio) test @ October 7, 2010

In that article, ruhtinas was linked good example of audio quality from ilmojk‘s youtube video.

Nokia N8 HD Skädäm-Katujen kuningatar

Here is one more good example.

Nokia N8 Camera test – U2 Roma 10.2010

In entrambi i casi non abbiamo utilizzato nessuna patch che porti foto a massima qualità o video a 30FPS.
[google translated: In both cases we did not use any patches that bring the highest quality photos or videos at 30FPS.]
It means audio wasn't edited, I think.

Last two videos were low light or night recording so video quality wasn't that great but audio makes video more watchable and enjoyable.

So Nokia N8's two microphones make so special in video recording.
This is the reason I could say Nokia N8 was exceptional. I haven't even hands on N8 though.

Saturday, October 2, 2010

Nokia N8 was shipping and this is new promo ad

Nokia N8 started shipping yesterday. But it will take some time to reach end-user. <-- Old link doesn't work.

So if you are waiting for Nokia N8 or wanted to know about Nokia N8, you can see this promotional video. <-- Old youtube doesn't exist anymore.

This video showing well about what Nokia N8 can do.

Wednesday, April 30, 2008 moving forward in the gadget business

When I was trying to check the's homepage, I saw the letter from the CEO for restocked the Kindle which is wireless reading device.

Kindle image via Wikipedia

If you know how unusual that put the CEO's letter in the their very first page. Have a look at this.
Picture taken from at 2:15 29th April 2008.

If you think it is just digital gadget such as smartphone and iPhone, you should better think about it again.
Because, device was not the issues here.

What this letter mentioned is that they added 25,000 additional books, blogs, magazines, and newspapers which bringing the total to more than 115,000. A hundred fifteen thousands.
I will just briefly tell you about the history of ebook viewer. Almost none of portable gadget succeed in the market, before E-ink came out. E ink screen is most comfortable for human eyes-I haven't seen it yet but a lot of people talked about that way.- and feel like paper because it is one of electronic paper technology.
So it is possible technology to make new big market.

Whenever I thought about it, I felt that was just online version of bookstore. I know their main business was not selling the book any more so they became online shopping mall long time ago.
So they don't have to sell the actual books in the future because they can sell the ebook.

I know it still need a lot of time but it will happen someday.
Kindle product –

p.s. I skipped a lot of details so some day I will write more about it.