I somehow forgot about a cool project I made over a year ago! I guess dental school got in the way of my productivity. It's a little ironic how the last post was about something I made a year ago screwing up, and this one is about something I made a year ago turning out well! Anyhow, the world's only battery powered microcontroller based handheld prime number generator I made last year (documented here, here, and here) got some new exposure this morning when it was posted on HackADay.com!
I'm absolutely amazed by how much I learned back in the days when I was working with electronics in the weeks before I began dental school. Perhaps it's also ironic that my learning decreased dramatically once I resumed graduate school... To give you an idea of how early in my electronics exploration this project was, look at the wires... they're made from phone cord! I had no wire at my apartment, so I had to scavenge it from whatever I could find, and I ended-up buying a 50ft phone cord at Wall-Mart (super-cheap I'd imagine) and harvesting the colored wires inside.
The code is a joke. There's no reason for this thing to generate numbers rapidly, so I used the absolute-slowest method for detecting primes possible. The schematic is a joke too. There's hardly enough current to ignite those LEDs! Notice how the video had to be filmed in a dark room. Ironically enough also, the crystal isn't even being used! It's just for show! I'm confident I never changed the ATTiny2313's fuse bits to rely on th external crystal, so it's probably running on the 4MHz internal RC oscillator (perhaps with the /8 fuse set by default, so 500kHz?)