Raspberry Pi CM4 IO Board

Overview

The Raspberry Pi CM4 IO Board is Raspberry Pi's official reference carrier board for the Compute Module 4. It is a development and prototyping platform designed to make all CM4 connectivity accessible without requiring a custom carrier board, serving both as a reference design for engineers and as a functional standalone system for developers. The CM4 module itself is not included and must be purchased separately.

The IO Board exposes the full capability of the CM4's high-density connectors through familiar, standard-sized ports. Two full-size HDMI 2.0 connectors support dual independent 4K display output. A Gigabit Ethernet RJ45 port provides wired networking with optional PoE via a standard HAT. Two USB 2.0 Type-A ports handle peripherals, with a header adding two more. A Micro-USB port provides access to the CM4's USB boot mode for programming the onboard eMMC of non-Lite variants.

Expansion options are broad: a single-lane PCIe Gen 2 x1 slot enables NVMe SSDs, Coral TPUs, or other PCIe cards via a standard M.2 adapter or PCIe edge connector. Two 22-pin FPC connectors provide dual MIPI CSI-2 camera interfaces and two 22-pin FPC connectors provide dual MIPI DSI display interfaces. A standard 40-pin Raspberry Pi HAT header maintains backward compatibility with the entire HAT ecosystem. A microSD slot serves CM4 Lite variants (those without eMMC).

Board-level features include a hardware real-time clock with battery socket, a standard fan connector, and jumpers for disabling the CM4's wireless module or enabling EEPROM write access. KiCad source files for the IO Board are published by Raspberry Pi for use as a reference when designing custom carrier boards.