NVIDIA and libfreenect2: How to fix undefined reference to ‘clReleaseDevice’ and ‘clRetainDevice’

Because AMD and Nvidia provide different versions of the OpenCL header, the following error can occur compiling a program using libfreenect2 and a Nvidia GPU.

/usr/local/lib/libfreenect2.so: undefined reference to `clReleaseDevice'
/usr/local/lib/libfreenect2.so: undefined reference to `clRetainDevice'

This error can be fixed by installing:

sudo apt-get install ocl-icd-opencl-dev

After the installation, the undefined reference should be fixed.

RaspberryPi: Autoconnect to WLAN (WPA2)

In most applications in robotic it’s necessary to get rid of the ethernet cable to move the raspberry free and battery powered. Luckily the Raspberry PI supports a variety of USB-WLAN-Sticks like the TP-Link TL-WN821N. In this tutorial I describe how you setup the WLAN connection that the RPi auto connects to your WLAN after you switch on the power.
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