Opus BT-C100 reverse polarity protection

I recently bought an Opus BT-C100, as unlike my other Lithium Ion chargers, has a discharge test feature. It also fairly quickly estimates internal resistance of the cell, which is a good health indicator.

Unfortunately due to A123 26650 cell being of upside down construction I released the magic smoke out of the Opus BT-C100 by reversing polarity. The smoke escaped through the battery holder slit.

Continue reading Opus BT-C100 reverse polarity protection

Dealing with data obfuscation in some Chinese dash cameras

This is post relates to the extracting GPS coordinates form Novatek based dash cameras.

About an year ago I was contacted by someone who tried to use my script on MP4 files generated by their camera, only to get garbage data out. It appeared that the camera was obfuscating the coordinates stored in MP4 (the speed and heading was recorded correctly). It was not a bug because provided player was decoding them correctly.

Continue reading Dealing with data obfuscation in some Chinese dash cameras

GT06E GPS Tracker Part 2: Establishing connection

This is a continuation from Part 1.

As of writing this I already had complete solution (as far as getting tracking data is concerned), a multi-process TCP server with a mysql database back-end.
The server code itself is not pretty thus I am cautious about sharing it at this stage (I will “open-source” it once I cleaned it up).

One caveat: my solution does not support batch mode (where the payload contain multiple concatenated location and other packets).

The assumption is that the reader is somewhat familiar with python and sockets.

Continue reading GT06E GPS Tracker Part 2: Establishing connection

Hate ads on your smart phone? Pi-hole it permanently!

Sorry about spammy headline ;).

Below I will describe how I got rid of ads on my android phone without rooting it.
It is very easy to get rid of ads on an android smart phone if you have root access. Unfortunately pesky manufacturers insist on declining warranty if the phone is rooted.
I will probably one day test this is in small claims court for a cheaper phone. I digress…

The requirements:

  • Some linux box/container/VM. In this post I used Ubuntu 16.04 LTS
  • Public IP on the box from above
  • Some linux/cli/unix experience

How does it work?

  1. Smart phone connects to the Linux box via OpenVPN
  2. Linux box is running Pi-hole which acts as a selective DNS server
  3. ???
  4. Proft!

Continue reading Hate ads on your smart phone? Pi-hole it permanently!

mod_python: 404 on *.py when trying to download the file

I had mod_python enabled and it would give me 404 on random python scripts in downloads directory (not cgi)…
Nothing in error log either!

Here is the fix:

put .htaccess file in the download directory with following contents:

<Files *.py>
    RemoveHandler .py
    AddType text/plain .py
    SetHandler none
    SetHandler default-handler
    Options -ExecCGI
</Files>

External Western Digital USB drives and why to avoid them

Today I encountered a dead Western Digital USB 2.5″ drive.
The drive in question is “WD 1TB Elements SE Portable Hard Drive USB 3.0” with WDBPCK0010BBK-01 part number.
Searching for the part number on WD site leads nowhere.

The error was:

 Buffer I/O error on dev sdb, logical block 0, async page read 

Continue reading External Western Digital USB drives and why to avoid them

HUSQVARNA rip-off pricing in NZ

So, I came across an interesting, but not surprising thing with Husqvarna MSRP prices in NZ compared to USA.

I recently looked at Husqvarna 445 and when googled for it, I got multiple MSRP prices (one for NZ, on for AU and another for USA).

Husqvarna 445 MSRP by country:
USA: 329.95 USD

AU: 899.00 AUD (~$690 USD)

NZ: 1019.00 NZD (~$745 USD)

According to NZ customs duty calculator using US MSRP price as base the fair MSRP price in NZ should have been $599 NZD (~$440 USD).

What is with the ~$150 USD price difference between NZ and Australia? According to Husqvarna Americans are twice better than Australians and more than twice better than Kiwis. They treat Kiwis like chumps that will buy thing at whatever prices Husqvarna feels like.

Guess what, from now on I will be avoiding the Husqvarna until these greedy corporate types will pull their heads out of their asses and set fair MSRP prices. In this global economy it is very stupid not to have standardised prices across the globe.

If I really wanted to buy one, no way in hell I would be buying it in NZ, as for about $150NZ I can get it shipped from the states.