FPGAs (Field-Programmable Gate Arrays) are just now starting to gain traction in the maker community, but they remain a bit of a mystery to many people. It’s easy enough to understand what they do, which is create real hardware ICs (Integrated Circuits) based on your instructions. But actually figuring out how they do that, and how to program them, is quite the challenge. Mahesh Venkitachalam has been learning about FPGAs, and decided to use his new knowledge to make FPGA earrings for his wife’s birthday.
Each earring is a PCB and has a Lattice iCE40UP5k FPGA chip and a 8x8 grid of SMD (Surface Mount Device) LEDs. That grid of LEDs can be used to display scrolling letters, Conway’s Game of Life, or a simple blinking pattern. The only other components on the PCBs are a CR2032 coin cell battery holder, a voltage regulator for the FPGA, an SPI flash chip to store the bitstream for the FPGA, and an oscillator for the clock. The assembled PCB earrings are a tad big and heavy, but Mahesh says they’re similar to the kinds of earrings his wife already likes to wear.
To create these earrings, Mahesh enlisted the help of his friend and engineer Siva. Mahesh handled the big picture design work and programming, while Siva did the PCB design and assembly. One notable thing about the schematic is that it doesn’t include a shift register. Instead, to keep the BOM as small as possible, the LED matrix is connected directly to the FPGA’s pins. The PCB was designed as a 4-layer board in Altium Designer, along with a special pogo pin adapter for programming the FPGA. The finished earrings look fantastic, and are probably one of the most unique uses of an FPGA we’ve seen.