Monthly Archives: October 2012

Hellschreiber

What do you get when you mix a cheap MSP430 development board with a simple oscillator circuit and blend in a handful of code from various sources? Hellschreiber- a radio transmission mode invented in the 1920s.

image

MSP430 Launchpad and Oscillator

The screenshot above shows the signal as transmitted across my bench – a distance of about 50cm. The text being transmitted is “G7UVW / QTH / JO01BN / QRPP / Hellschreiber”. The slanting of the text is due to the drift in frequency between the transmitter and receiving radio and also timing errors in the transmitting code.

Game of life

Conway’s Game of Life is a mathematics puzzle / toy / serious bit of research that I mess with from time to time; usually when I get a new computer and want to see how fast it is compared to older ones. I wrote a basic GoL simulation for the Sinclair Spectrum back in the early 90s.

In the last few days there have been a smattering of posts on Twitter that have sparked my interest in the GoL again. First was Charles Stross linking to a GoL simulation simulated in Gol, which amazed me. I knew that type of simulation in GoL would be possible, because GoL is a Universal Turing Machine, I’d just never seen anything that complicated done in GoL.

The second spark was a post by Mark VandeWettering with a FFT based GoL simulation. His post includes example code, so I gave it a try. The output is a bunch of PGM image files, to convert these to video to see how the simulation progressed I used ImageMagick and ffmpeg.

#First off, convert the pgm files to something ffmpeg can handle
$ for f in *pgm ; do convert -quality 100 $f `basename $f ppm`.png; done

#Then set ffmpeg loose on the new images to make a video
$ ffmpeg -r 10 -b 1800 -i frame.%04d.pgm.png out.mp4

This is the resulting video – it wasn’t a particularly interesting output from the sim. If I keep playing with GoL I may post something more appealing.