This is the magic sauce in our 7-segment and matrix backpacks, now available in breadboard-friendly breakout board format. The HT16K33 is a neat little chip that has the ability to drive a multiplexed 16x8 matrix (that's 128 individual LEDs). The communication protocol is I2C so it uses only 2 pins, and you can have up to 8 selectable I2C addresses so thats a total of 8 matrices, each one ...