DIY Smart Door für 5 Euro (Android App - Part 3)

  • Posted on: 2 November 2016
  • By: robin

Die App hat genau 2 Aufgaben: Sie soll es ermöglichen die Tür aus der Ferne zu öffnen und uns über Klingel Events per Notification informieren. Das ist nicht viel Programmieraufwand, aber trotzdem interessant. Zum realisierung wird nämlich Firebase verwendet und die unter euch die Firebase für eine Android App noch nicht verwendet haben werden heute etwas lernen.

Die App:

DIY Smart Door für 5 Euro (Door Bell - Part 2)

  • Posted on: 30 October 2016
  • By: robin

Das ist Teil 2 des Smart Door Projektes. In diesem Teil geht es um das abgreifen des Klingelsignales. Wie bereits im 1. Teil, schauen wir uns zunächst die Kontakte der Platine an.  Beim Ritto Twinbus Wohntelefon 7630 finden wir diese auf


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.