Blinkenlights

Blinkenlights has a very silly history, even by my standards. It starts with me, crewing at a LARP, thinking "this prop we made on the spot would be a lot more interesting if it had some flashing lights". So when I got home, I wrote a bunch of OK-ish Arduino code for doing exactly that, along with the appropriate hardware to run the code (an AliExpress Arduino Nano clone and some LEDs). I also wrote some code to let me use a second AVR-based device as a programmer for the AVR doing the actual blinking. The idea was that you'd be able to program the lights without me needing to bring my entire laptop to LARP.

Then I took a not-very-brief diversion to write my own AVR assembler in Forth, for no reason other than for fun (writeup on that Soon™). When I finished that, I came back and rewrote Blinkenlights in assembly, and managed to get it down to about 0.5% CPU usage (as in, the CPU was spending more than 99% of the time asleep). I was also able to increase the PWM resolution to 10 bits (rather than 8) because I wasn't going via the Arduino library routines. This means it looks nicer at low brightnes, because of the whole lin-log brightness perception thing.

And THEN it collided with another thing I'd been meaning to do for ages - computer controlled fairy lights. I bought a battery-powered set from Aldi years ago and never did anything with it until recently. The process started with some surgery: I cut the light string off the battery box, then desoldered the wires between the actual battery holder and the little control board, then pulled out the control board. So then I was left with a probably slightly waterproof (but I wouldn't trust it) battery box and a string of lights.

The original set took 3 AA batteries, nominally 4.5V. However, because of how LEDs work, trying to run it directly off 4.5V or 5V causes a huge voltage drop, down to about 2 or 3V. This is where I stalled out a bit, because I didn't have any DC-DC converters in my parts bin, and uni work was starting to ramp up. Hopefully I'll get some time over Christmas to put a parts order in and actually put something together.

The Blinkenlights connection is fairly obvious here. I have some software for controlling lights, and I have some lights I want to control. The hardware to connect them should be pretty simple - a buck converter and a MOSFET should do the trick - but I'll inevitably run into some analog weirdness along the way. Watch this space.