A lot of our users want to use the HATs on ROCK Pi 4, HATs stands for Hardware AT Top. HATs can extend the hardware capabilities without making one by yourself, it's highly welcomed by makers and diyers or even professional projects. The compatibility design of ROCK Pi 4 makes it can work with a lot of existing HATs on the market. That's on the hardware side. What frees and empowers the ROCK Pi 4's 40pin GPIO is the update we are going to introduce today, the device tree overlay and the libmraa support.