What is b9 board?

As an AI language model, I assume that you are referring to the BeagleBone Black Rev B9 board.

The BeagleBone Black Rev B9 is a small, affordable, and open-source computer board designed to bridge the gap between microcontrollers and full-size PCs. It features an ARM Cortex-A8 microprocessor, 512MB of DDR3 RAM, and 4GB of eMMC storage. The board also includes Ethernet connectivity, HDMI output, USB ports, and support for a variety of expansion boards.

The BeagleBone Black Rev B9 is particularly popular in the DIY electronics community, where it is used for applications such as robotics, home automation, and Internet of Things (IoT) projects. It runs the Linux operating system and supports a variety of programming languages, including Python, C, and JavaScript.

Overall, the BeagleBone Black Rev B9 is a versatile and powerful board that offers a lot of value for its relatively low price.