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Dirk Grappendorf
grappendorf.net
grappendorf.net
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Smarkant - Convert your IKEA Bekant table into a smart IoT device

This work extends the IKEA-Hackant project from Robin Reiter, who reverse engineered the controller board of an IKEA Bekant motorized adjustable table.

In my project i connected an ESP-12F module (ESP8266) to the Arduino which gives us WiFi and quite some processing power to add additional IoT functions
to the Bekant table. I've implemented an Alexa Skill, which when activated with a voice command, calls an AWS Lamda function which in turn sends a REST message to the AWS IoT backend. This backend then sends an message to our controller which finally moves the table.

http://www.grappendorf.net/projects/smarkant.html

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This is a wake-up light that simulates the sunrise by gradually increasing the brightness of its LED light during a configurable period of time before the alarm time.These wake-up lights are produced by a number of manufacturers, but here i'm building my own with a Raspberry Pi, a handfull of electronic components, the programming language Elixir and Nerves, an Elixir framework for developing software for embedded systems.

This project explores how Elixir/Erlang OTP and Nerves can be used to develop robust and thoroughly tested embedded systems. The project description consists of three parts: part one explains the circuit diagram and the physical construction, part two talks about the architecture of the firmware software and in part three i explain how we can implement automated tests that verify our software specification.

https://www.grappendorf.net/projects/sunrise-alarm-clock/

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This is a wake-up light that simulates the sunrise by gradually increasing the brightness of its LED light during a configurable period of time before the alarm time.These wake-up lights are produced by a number of manufacturers, but here i'm building my own with a Raspberry Pi, a handfull of electronic components, the programming language Elixir and Nerves, an Elixir framework for developing software for embedded systems.

https://www.grappendorf.net/projects/sunrise-alarm-clock/

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This is a wake-up light that simulates the sunrise by gradually increasing the brightness of its LED light during a configurable period of time before the alarm time.These wake-up lights are produced by a number of manufacturers, but here i'm building my own with a Raspberry Pi, a handfull of electronic components, the programming language Elixir and Nerves, an Elixir framework for developing software for embedded systems.

https://www.grappendorf.net/projects/sunrise-alarm-clock/

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Elixir/Nerves, Pi Zero and Edimax EW-7811UN WiFi

This tutorial shows you how to solder a USB WiFi
dongle directly onto the Raspberry Pi Zero board and how to enable the Kernel driver in a custom Elixir/Nerves system image:

http://www.grappendorf.net/tutorials/nerves-pizero-edimax.html


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Control a 2-port KVM switch via HTTP over WLAN with an ESP8266
http://www.grappendorf.net/projects/wlan-kvm-switch.html

Recently I bought a small and inexpensive 2-port KVM (DVI/USB) switch that I installed with the intention to switch between my Linux and Windows workstations. Marketing promises that I could switch by pressing Scroll-Lock or Ctrl on my keyboard two times. The sad reality is: this only works if the currently active workstation is the Windows one (WTF!?).

This article briefly describes how you can add an ESP8266 module to a KVM switch, which allows toggling between the two computers by sending a REST/JSON request via WLAN. You can then define global keyboard shortcuts that simply call httpie to send the toggle request to the switch.
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Control a 2-port KVM switch via HTTP over WLAN with an ESP8266
http://www.grappendorf.net/projects/wlan-kvm-switch.html

Recently I bought a small and inexpensive 2-port KVM (DVI/USB) switch that I installed with the intention to switch between my Linux and Windows workstations. Marketing promises that I could switch by pressing Scroll-Lock or Ctrl on my keyboard two times. The sad reality is: this only works if the currently active workstation is the Windows one (WTF!?).

This article briefly describes how you can add an ESP8266 module to a KVM switch, which allows toggling between the two computers by sending a REST/JSON request via WLAN. You can then define global keyboard shortcuts that simply call httpie to send the toggle request to the switch.
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Yet another Arduino-based signal tower (aka stack light) that can be used to display the status of anything that requires immediate maintenance in case of a failure (I'm using it as a continuous integration status indicator for our agile software development team).

The article linked down below describes the construction of this signal tower with a WLAN interface and a simple HTTP REST API. 

http://www.grappendorf.net/projects/signal-tower.html
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Yet another Arduino-based signal tower (aka stack light) that can be used to display the status of anything that requires immediate maintenance in case of a failure (I'm using it as a continuous integration status indicator for our agile software development team).

The article linked down below describes the construction of this signal tower with a WLAN interface and a simple HTTP REST API. 

http://www.grappendorf.net/projects/signal-tower.html
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I finally finished my 6502 CPU retro computer system.

http://www.grappendorf.net/projects/6502-home-computer

https://github.com/grappendorf/homecomputer-6502

The 8-bit MOS 6502 CPU was used in many popular home computers of the 1970s and 1980s like the Commodore 64 or the Apple II.

This project started with some basic circuit designs on a breadboard, went on with the production of a PCB, the development of firmware software, and finally finished with a custom designed 3D printed case.

I have published a short seventeen part article on my website that illustrates the complete development process.

All the schematics, PCB design files, and the source code are released under open source licenses on Github. The repository also includes various versions of these files, so that you can retrace my development progress.
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