robin's blog

HowTo: Raspberry start command on startup with tmux

  • Posted on: 27 October 2016
  • By: robin
autostart command as specific user

What you want is to automatically start a script or programm when your raspberry pi boots. And you want so specify a user which is executing the process. Even better, you want to start it in a tmux session because this allows you to attach to the session and see whats going on. You are awesome. But you don't know how to do it ? Simply follow this simple steps:


1. Create a bash script file (e.g. with: touch tmux_start).

2. Add the following lines to this file (e.g. nano

Retrofit2 + RxJava: "Unable to create call adapter for rx.Observable"

  • Posted on: 28 July 2016
  • By: robin
If you have trouble with Retrofit2 and RxJava you should doublecheck you Retrofit setup. To be honest I write the blogpost because it happend to me and I did not found a good answer on google.
A really common exception that you get when when Retrofit2 is missing the right call adapter is this:
Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: Unable to create call adapter for rx.Observable<java.util.ArrayList<java.util.ArrayList<java.lang.String>>>

Android Lesson Learned: Drawable vector is ignoring color (svg shown black)

  • Posted on: 24 June 2016
  • By: robin

What you need to know when you want to support versions older than L and want to use vector (svg) drawables is that you cannot use the @color thing to pick your color. You need to take the oldfashion way with #HEXCODE. If you don't this will lead to black vector graphics on all devices running something older than L.

How to build an Electric Skateboard - Part 1 Research

  • Posted on: 12 June 2016
  • By: robin
electric skateboard

I think, 2 years ago I heard the first time about electric skateboards and I immediately wanted one. But at this time there where no good parts for mounting the motor(s). All electric stakeboards that you can buy are at least 900 Euro. I want that cheaper.

This week I even stumbled upon a Longboard at TK MAXX (or TJ MAXX) for just 70 €. Essential for this project ;-)

So I will do some reasearch and buy parts for my electric skateboard.

Magic Mirror - Turn off screen --> save energy

  • Posted on: 6 May 2016
  • By: robin

My Smart Mirror is running 24h a day. I unplug the screen at night but well that really impractical. From our server-dashboard at work (3 HD TV displaying server load, memory, cpu usage etc.) i knew that it is possible to turn off the screen programmically on the raspberry pi. I wrote a short python script which allows you to shut down the screen by calling a url. I had in mine.1. The one that I already presented2.