So that does not work any more (i assume the Linux kernel was changed in some respect). That's why i chose the boring way of using an arduino, which has the advantage, that it now can be run from any Linux computer, although the raspberry pi can still be used in longterm installations.
connect the Arduino. install the sketch from the Git repository onto the arduino. connect the rgb band to pin 7 and the powersupply. You are now connected. Try the console manager in arduino, set the speed to 4900 baud and send the string "rgbx". It should now have a red, a green and a blue glowing led. everything is set up
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Step 3
cd src
run the software. Although there might be a compiled version included recompile it with javac -sourcedirectory ../../....... ///
and execute with java com.asdf....Main > /dev/ttyUsb
Now the gui can be used to create turingmashines and run them.
however the raspberry pi can do pwm, due to hardware features, and i found a softwoare (no linked in), that uses direct memory aces (dma) to magically toggle the pin without the ALU (the part of the CPU, that does most of the calculation and program execution work) involved.
I can't understand how it works (it writes directly to memory and has to run as root as a consequence), but it works well. what more could I wish for.
I thought that ws2812 strips couldn't be controlled by Pis as they can't supply a 400khz clock signal to keep them in sync? I thought they were only control able by non-os machines.
it appers to not work annymore with new cernels, i might look into it