Rob K1WAW was trying to sharpen his Morse code skills and wanted to use an Iambic Keyer. He built this prototype which connects the left and right paddle of the telegraph key to pins on the MSP430 Launchpad, which is programmed to produce the dot/dashes and output it to a speaker at an audio tone of 781.25Hz. (There’s an RC filter and a transistor connected to audio output.)
The code and comments are found in this post.
Via Four-Three-Oh!