Posts

A closer look at the Got-It Bluetooth tags

Jan 8, 2020

Intro # When I first heard of the Got-it Bluetooth tags, I just had to order a preview set. Those are active Bluetooth Low Energy beacons, embedded into a thin and flexible sticker, including battery. The proposed use case is asset tracking in commercial settings. They are 28mm x 76mm x 0.75mm Battery life is supposed to be one year Waterproof, flexible A preview set containing 10 stickers costs 99$, they plan to get the price down to $1/sticker Some pictures provided by Got-It here How I received my labels: ...

How to buy a car in the US as a foreigner

May 3, 2019

When I went to the US last year on a J-1 visa, I had to figure out how to buy a car. I had never owned a car before, and I obviously did not have a US driver license. If you are thinking about buying a cheap car for a road trip in the US to save on rental costs, it is probably not worth it: buying a cheap beater car exposes you to the risk of it breaking down, which will then cost you a lot of money to fix it. ...

3D waterfall plot in WebGL

Jan 27, 2017

In 2016, I finally learned OpenGL. So I decided to ditch THREE.js and rewrite my old Waterfall-Plot project in pure WebGL. The only external Javascript library used is gl-matrix for matrix transformations. All the line offsetting (z-direction in time, y-direction for frequency magnitude) is now done directly in the shader. This makes the animation much smoother, as no THREE.js points/lines have to be created and destroyed anymore. It also allows more flexibility in color effects. ...

ETH supercomputing for beginners

Aug 25, 2015

Disclaimer: for this to work, you must be an ETH Zurich affiliated person and own a nethz-account . So, you wanna play around a bit with machine learning. Or run a crazy particle physics simulation. But you only have a lame Macbook. Your gaming rig would do the job, but its fans are spinning so loud your neighbors complained. Solution? Just use ETHs Euler general purpose super computer ! Even though they explicitely write that Euler is “not a supercomputer”, supercomputer just sounds cooler than “general purpose” computer. ...

Javascript 3D waterfall plot

Aug 18, 2015

For a long time, I wanted to try out WebGL. After some initial research, it became clear that it is not that simple to use WebGL without having prior experience with OpenGL. Thats why I settled with THREE.js . This library abstracts away all the WebGL things and gives you a nice 3D interface. I like the Joy Division Unknown Pleasures album cover. You can find something about its history here . ...

Wifi monitor on a Raspberry Pi

Aug 1, 2015

I had a Raspberry Pi and an old analog volt meter lying around. To finally do something “useful” with it, it was decided that our CoWorking Space needs a WiFi detector. Functionality in short: It captures WiFi packets from the air, and counts them. This then gets mapped to a scale from 0 to 10, and displayed on a rainbow-colored LED chart. Hardware # This runs on a Raspberry Pi Model B, although all the other models should work too. ...

Telegram CLI on Raspberry PI

May 11, 2015

Telegram is an (encrypted) messenger service which also offers an API. This makes it ideal for bots and automation. Here it is shown hot to set up telegram-cli on your Pi. Get a shell on your RasPi, I prefer to do this over SSH. You can also plug your RasPi to a screen and ann a keyboard. Build # sudo apt-get install -y git sudo apt-get install -y libreadline-dev libconfig-dev libssl-dev lua5. ...

Hack the spectrum - Hide images in Audio files

Jan 7, 2015

Intro # You have probably heard of the song [Equation] by Aphex Twin. It is known for having a scary face hidden in its frequency spectrum . So I asked myself, how can I do this by myself? It is possible using a bit of matlab and basic knowledge in signal processing. I choose a short mp3 track to modify: Cartoon (Interlude) by French House Artist SabastiAn. This is the image we’ll try to hide: ...

Painless way to install NumPy & Co. on OSX

Dec 1, 2014

When working with scientific data, NumPy, SciPy etc. are often used. They can be quite a pain in the ass to setup: many dependencies, some modules have to be compiled (which sometimes works…), so often PIP does not work out of the box. Also, the Apple Developer Command Line Tools have to be installed for this to use the compilers. The very simple solution to this is Anaconda , a Python distribution containing almost anything would ever want: NumPy , Skikit-Learn , and also file format libraries like H5Py . ...

Migrating Gitlab from MySQL to Postgres

Apr 23, 2014

Recently, I migrated Apovedas Gitlab installation from using MySQL as database server to PostgreSQL. Thats because until now, I have used the manual gitlab setup guides, and I now want to change this to use the automatic setup/provided packages, which all use postgres. Install Postgres and create the database # (Taken from the Gitlab installation manual ): sudo apt-get install -y postgresql postgresql-client libpq-dev # Login to PostgreSQL sudo -u postgres psql -d template1 # Create a user for GitLab. ...