IO Board for Raspberry Pi CM4 CM4 is a Raspberry Pi s computer module that is without the IO connectors. My job was to Design IO Board for the CM4 in a compact size with onboard 36v Power input support. it was challenging work but after the testing and prototyping of one design, we successfully completed it. The IO (Input Output) PCB supports HDMI Display Port, USB, Audio Output, USB C, and Power Input ports.