Add lots more outputs to a microcontroller system with chainable shift registers. These chips take a serial input (SPI) of 1 byte (8 bits) and then output those digital bits onto 8 pins. You can chain them together so putting three in a row with the serial output of one plugged into the serial input of another to make 3 x 8 = 24 digital outputs. You can chain pretty much as many as you want. This makes it easy to control a lot of outputs like LEDs from only 3 digital microcontroller pins. https://elecena.pl/product/17497879/74hc595-shift-register-3-pack 2021-04-06 https://elecena.pl/product/17497879/74hc595-shift-register-3-pack 2022-03-14