one time [Lambert the Maker] When he saw the Arduboy, he knew it would be the perfect thing to remix into a business card with an 8×8 LED matrix instead of an OLED screen. [Lambert] I already have a PCB business card for work, but it doesn't seem to be of any use, so this snake card is for my personal information.
The brains behind this operation is an STM32F0, and programming the LEDs required a bit of ingenuity. According to the datasheet, the maximum current that can flow through a particular GPIO pin is 30 mA. The LEDs are running at 20 mA through a limiting resistor, so the code only switches on one LED at a time, making sure the previous one is off. The whole screen is updated every 125 ms, with a persistence of vision effect to make the animation look good.
In the short video after the break you can see a preview, followed by short videos of versions 1 and 2. The prototype was built in 2020, when Board House only offered green PCBs in its assembly services. Fast forward to 2024, and Board House is now offering colors other than green.
Version 2 is actually thinner than a credit card and has tiny buttons instead of a Cap Sense pad for input. [Lambert] It also adds a floating ADC pin that acts as a random number generator, placing the apple in a new position every time the game is powered on.
