Monday, 26 October 2015

Removing "Whats New" app from Sony Xperia Android smartphones

Sony Xperia smartphones come with a number of Sony crapware, one of which is the "What's New" app that runs in the background and popup from time-to-time as a notification, which is just plain annoying for some of us. Worse, unlike the other crapware, this one cannot be disabled in "App Info" (the "Disable" button is greyed out).

After some research, I found a way to disable this app. First you need to have a working ADB in your system. The trickiest part is to install the correct ADB driver. I referred to this post for help. On my Win7 x64 system, the AdbDriverInstaller method worked for me.

If you don't have adb.exe yet, you need to get it into your system. The official way is to install the Android Platform SDK, but a minimal install of ADB can be found here.

Anyway, to verify that ADB is working properly (both EXE and driver), at the command prompt (with the device connected to the PC via USB cable), type:

adb devices

This should display something like:

List of devices attached
YT91152XZY      device

i.e. there must be at least one device attached.

So much for the prerequisite. The rest is simple. Simply execute the following commands:

adb shell
pm hide com.sonymobile.entrance

That's it!

Older posts on the web recommends pm block com.sonymobile.advancedwidget.entrance, which does not work anymore. So this is a note to myself (and others) to hopefully save some time in case I reset the phone and need to perform this step again in the future.

Monday, 1 June 2015

"System repair disc could not be created. The parameter is incorrect. (0x80070057)"

The simple answer to this error is I was using a CD-R disc instead of a DVD-R disc.

I got stuck for almost 30 minutes googling around and trying out all kinds of suggestions. Then after downloading ISO image and trying to burn it to the disc using ImgBurn, I got an error message in human language telling me the disc has incorrect format. Could be better, but I got the hint.

Developers, we need error messages that a human being of average intelligence can understand.

Sunday, 26 April 2015

Cleaning Roomba's front wheel

You learn something new everyday.

I have been using the Roomba for the past 5 years at least without realizing that the front wheel needed cleaning. I clean the side wheels and the brushes religiously, occasionally using the air compressor, but front wheel, nah.

That's until one of the Roombas started making a funny noise. When it runs, it would sound like it's going over a hump every second. I have heard that before when the bottom brushes are not properly fitted, but this time the problem is not that.

I finally traced it down to the front wheel. I noticed it does have quite a bit of hair stuck in the axle. After struggling on my own for awhile to figure out how to clean the damn thing properly, I turned to YouTube:


Turned out it was pretty easy. You just pull the wheel carrier right off with a bit of force, then pop the wheel off with a flat blade screwdriver. Then I found the culprit:

It's a tiny bead from my daughter's DIY necklace toy set, stuck right between the wheel and the carrier. Problem solved.

Of course, pull all that hair and debris off the front wheel axle makes for much cleaner operation overall. So one more thing to add to the Roomba cleaning checklist!

Friday, 9 May 2014

Strange problem on KVM VPS

This one for the X-Files.

I have been helping a client migrate his web server from one VPS to another because he needed more disk space. His previous VPS is based on Xen, and the migration is to a KVM-based VPS.

Everything was smooth-going at first. I installed Debian 7 x64, all the usual packages: nginx, php, mariadb etc. Easy. Configured and tested the setup. Easy.

Then I migrated his database and web server over and asked him to do some business-side testing. That was when we hit an unusual snag. His PayPal IPN wouldn't work.

At first, I traced the logs, thinking it was some kind of PHP code incompatibility. Nothing. The code will break at this point:

   $fp = fsockopen('ssl://', 443, $eno, $estr, 30);

and never return.

I was stumped. So I wrote a simple test program that retrieves the HTTP and the HTTPS version of Lo and behold, the HTTPS fetch breaks right at that point with:

    Illegal instruction

I looked up what that means and found that it is just another name for the good ol' core dump. Shocked, I ran the same code on the Xen VPS (running the same Debian 7 and PHP version) and the code ran OK.

A number of searches did not turn up anything useful on this problem. It doesn't seem anyone else has encountered this. Having run out of ideas, I reported the details back to my client and suggested that he migrate to a Xen-based VPS instead.

I hope one day I will find out what this was all about...

Bluetooth headsets: Samsung HM1700 vs Plantonics M25

I had been using a Samsung HM1700 headset for over a year now. Recently, the Plantonics M25 was on sale. It looks a lot smaller, lighter and sleeker than the Samsung HM1700, it supports A2DP, it has long battery life, so I bought one to have a try.

The thing about Bluetooth headset is that you can never tell how well it works for you from the specs. You have to live with it for a week or two before you can tell if the two of you are compatible, sorta like a roommate or girlfriend. So I lived with the M25 for a week.

Samsung HM1700

  • Long battery life
  • Great reception
  • Bigger and heavier
  • Ear loop is not as comfortable
Plantonics M25

  • Long battery life
  • Sleeker, smaller and lighter
  • Ear loop is fitting and comfortable
  • Too many A2DP dropouts for my liking. By that, I mean the A2DP stream will drop out for a second or two being picking up again. This happens when I turn or bend my body, pick up a tool etc. It happens with the HM1700 too, but much less frequently.
So it seems like I will be sticking with the HM1700 for now and returning the M25. Let's hope something better comes along later at the same price point.

Friday, 14 February 2014

Bitcoin - Figures on transaction cost

Here are some figures on transaction costs in cross-border transactions.

Currently the de-facto reference currency in cross-border transactions is the USD.

A recent purchase of USD186 using the credit card resulted in the following line items in AUD:
  • AUD (from USD) - $202.00
  • Currency conversion assessment fee: $0.40
  • International transaction fee: $3.00
  • Cross border assessment fee: $1.60
Ignoring the spread used in the currency conversion, the transaction cost is about 2.5%. The actual transaction cost taking the spread into account is probably about 3+%

A recent purchase of USD700 using PayPal incurred a fee of $23 (buyer or seller pays). The transaction cost is a whooping 3.3%. I happened to have some USD in my account, so I didn't need to perform currency conversion. PayPal's spread in forex rate is notoriously poor compared to other avenues.

A purchase of 1.45BTC (approximately USD1085 at that time) incurred a transaction fee of 0.0002BTC, which is negligible. Speed rivals that of PayPal. Again, I happened to have some BTC lying around, otherwise conversion from fiat to BTC will incur additional charges, typically in the 2% range.

So if BTC (or some other crypto-currency) replaces USD as the de-facto reference currency for transaction, it should drastically lower the transaction cost. However, the price volatility of BTC is one factor that prevents this from happening. BTC needs to be relatively stable against other currencies before it will be widely adopted for cross-border transactions.

Friday, 7 February 2014

Bitcoin - Micropayment system for the Internet?

I have been dabbling with crypto-currencies, specifically Bitcoin and Litecoin, over the past 12 months. Everything from mining to e-commerce to currency exchange. I think I "get" the magic of the whole idea now.

For better or for worse, crypto-currencies drastically reduces the friction of money flow. You probably won't be able to find another means of moving money at a lower transaction cost, especially when small amounts are involved.

In addition, the speed of transfer is excellent for a distributed system. With Bitcoin, it takes a few minutes. With Litecoin, it takes a couple of seconds. The low transaction fee and fast transfer speed respect no geographical boundaries. It applies whether you are moving money within the same country, or between two countries on opposite ends of the Earth. Which probably freaked more than a few legislators out.

Plus this is a distributed system with no central authority to slow things down or screw things up. PayPal is fast, but try talking to the people who have had their PayPal accounts frozen at a whim and had to jump through hoops to unfreeze their account, sometimes without success. Also, PayPal's transaction fees are notoriously high (Visa/Mastercard's fees are even higher) and they have to impose random rules required by the powers-that-be of the countries they operate it. For example, in certain countries, PayPal now charges a fee for transferring money between two individuals regardless of amount, even though PayPal started out as an easy way for people to email small sums of money to one another!

It is therefore clear that crypto-currencies like Bitcoin have unique features to offer over existing systems, so it is not entirely frivolous. It has the potential to solve problems such as micropayment on the Internet, which until now has not taken off due to the high transaction cost and lack of standard, so we pay for content with our privacy via online ads. If one of the crypto-currency becomes de-facto standard, it should be quite straightforward to have a browser that will automatically tip the author when content is accessed, made worthwhile due to the low transaction fee.

Which is not to say there aren't teething issues to be resolved. The idea of keeping all the transactions that ever existed in a monolithic blockchain makes it huge, and it is unclear whether such a system can accommodate micro-transactions of this scale without also raising the transaction fee. But there are ideas such as making the blockchain itself distribtued, which should eventually make its way into the mainstream.

There is also currently a heated debate between inflationary versus deflationary crypto-currency. Quite a few crypto-currency are intentionally deflationary, and standard economic theory tells us that people will tend to hoard deflationary currencies, which is probably what is driving the massive speculative activity behind Bitcoin right now. For a crypto-currency to be used instead of hoarded, it probably needs to be mildly inflationary. And some kind of clever algorithm to dynamically adjust the rate of inflation based on economic activity would be nice!

Still, like other P2P technologies, I think the cat is out of the bag and there is no turning back the clock. The concept of distributed crypto-currency is here to stay and it will only evolve at the speed of software. Eventually, I think most, if not all, of the kinks will be ironed out, one or more standards will emerge, and there will be widespread adoption by netizens. The next few years will be interesting to watch in this space...