If you want to do something like connect a LED driver today, give SMBUS a try! It's basically I2C bus with some limitations, and a lot of motherboards bring it

If you want to do something like connect a LED driver today, give SMBUS a try! It's basically I2C bus with some limitations, and a lot of motherboards bring it out right via convenient headers. In general, I2C bus is a great way to interface with computers: it's needs only 2 wires, can be easily connected even to 8-bit MCU, and it has great development experience: start with $10 USB-I2C bridge (like CP2112) for development, then connect final device via internal SMBus connector or via unused monitor port. Linux comes with all the drivers, so there is no need to write kernel code. (You can also do USB, but this is annoying to implement from scratch, without any libraries. And USB-Serial bridge might be taken over by ModemManager and various embedded IDEs.)