My Work in February

DIY: 7 Segment Display

My work on the do it yourself 7-segment-display with two digits at the moment. It is a matrix of some led’s which are driven by a hardware board. The driver consists of two shift registers and some cords.

Seven Segment Display

Obviously there is a software part required to make useful things. However this project is still in an early stage and I will deliver some code and build instructions on my GitHub repository soon.

Actually I was looking for a cheap display big enough to fit my needs but I failed and constructed my own one in the size of 297x210 mm per digit. Costs are less then 5 Euros.

Web Application

Kitchen: Web App & Database

Recent work on my kitchen app. Since I started the project in june last year a lot of has changed. Some fixes and improvements are still required but I considerer this app in a good development state. Also, some tests would harden the project for the future and a better, responsive user interface would be awesome too. There is still some work and usually it is more then it seems to be at the moment. Due to lack of translation you can only visit a preview in german language. As mentioned earlier I publish only sources at the moment.


Airrohr: Measuring air pollution

A project to measure air pollution using the ESP8266 controller and SDS011 particle sensor. Background of the project is to motivate people building there own hardware and sending local air pollution data to a centralized place. At the end you get an overview on a map. Interestingly the project is designed to give all people without background knowladge the possibility to participate. Just follow the introduction.

That worked well but doesn’t fit my needs. I want to share the wireless hardware with a second project and have to modify the firmware. The project suggests using the NodeMCU firmware on the ESP8266 controller but it doesn’t. The original airrohr firmware is not scripted in lua. It is more a native application with some Arduino foo. This was a bit annoying because I ensured in advance to have the tools building the latest NodeMCU firmware. Now I decided to script my own measurement software using lua. But this is a story for the next article.

DIY: 7-Segment Display

Seven Segment Display

Reactions to Meltdown and Spectre

Meltdown and Spectre

A recent illustration* by CommitStrip got the point. Some researchers discovered a huge leak in the hardware which is accompaning our daily life. Many products are effected. This is a collection of some reactions and voices until now:



  • Intel: Intel Management Engine Critical Firmware Update (Intel-SA-00086)



  • TU Graz: Researchers discover serious security vulnerabilities
  • Alan Cox: Advice
  • LLVM: Introduce the “retpoline” x86 mitigation technique
  • Steinar H. Gunderson: Loose threads about Spectre mitigation


  • Anders Fogh: Behind the scenes of a bug collision
  • Raspberry Pi: Why Raspberry Pi isn’t vulnerable to Spectre or Meltdown
  • Apple: About speculative execution vulnerabilities in ARM-based and Intel CPUs
  • Amazon: Processor Speculative Execution Research Disclosure


In addition my laptop has reached the end of life and is no longer supported by the manufacturer and it looks like there are many systems they have the same problem. Many people don’t even know they have a problem. We all can only apply software patches if they’re reaching us. Holders of most smartphones just bought a buggy device. The dream of multi-user-tasking devices got disruptions. Actually, the whole idea of memory protection based on the hardware protection mechanism which separates the kernel space from the userspace.

If you’re still confused by the events which are shaking the IT world so much and do not understand why action is required maybe the XKCD can help.

*) Published with friendly permissions on a non-commercial blog.

Meltdown and Spectre are examples of what happens when we reason about security in the context of that abstraction, and then encounter minor discrepancies between the abstraction and reality.

Eben Upton

Papercraft Car

Papercraft Car

This is the design of a papercraft car based on a atmega microcontroller.


  • Automatic lights system
  • Forward ultrasonic radar
  • Inertial navigation system
  • Serial debug output
  • In-system programming

Future improvements:

CAN bus or I2C bus to exchange information between all the car components. A more robust and good looking design. The posibility to give wireless instuctions. All this this will increase the size of the car too.