# Raspberry Pi CM4 IO Board > Official reference carrier board for the Raspberry Pi Compute Module 4. Exposes dual HDMI 2.0, Gigabit Ethernet, 2× USB 2.0, PCIe x1, dual camera/display FPC, microSD slot (for CM4 Lite), RTC, HAT headers, and barrel-jack power. ## Quick Facts - **Brand:** Raspberry Pi - **Board Type:** dev-board - **Price:** ~$35 - **Product Readiness:** consumer - **CPU:** none (no onboard MCU; requires CM4 module) - **CPU Architecture:** N/A (carrier board) - **CPU Cores:** N/A - **RAM:** N/A (provided by CM4) - **Flash:** N/A (provided by CM4) - **Power:** +12V barrel jack or +5V (external) - **Operating Voltage:** 3.3V / 5V (from CM4 module) - **Antenna:** none (antenna on CM4 module) - **SD Card:** microSD (for CM4 Lite variants) ## Connectivity - **Wifi:** false (provided by CM4 module if WiFi variant) - **Bluetooth:** false (provided by CM4 module if WiFi variant) - **Zigbee:** false - **Ethernet:** Gigabit Ethernet (RJ45, PoE-capable with HAT) ## Open Source - **Firmware:** Yes - **Schematics:** Yes - **PCB Layout:** Yes ## Certifications RoHS, CE ## Compatible Firmware raspberry-pi-os, ubuntu, home-assistant-os ## Use Cases - iot-gateway - digital-signage - industrial-automation - smart-home ## Components - **CM4 Module Connector** (io-expander): Dual 100-pin Hirose DF40 board-to-board connectors accepting Raspberry Pi Compute Module 4. — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-shop.adafruit.com%2Fproduct-files%2F4787%2F4787_cm4io-datasheet.pdf&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) ## Protocols - **I2C**: SDA: GPIO2, SCL: GPIO3 - **SPI**: MOSI: GPIO10, MISO: GPIO9, SCK: GPIO11, CE0: GPIO8, CE1: GPIO7 - **UART**: TX: GPIO14, RX: GPIO15 - **I2S**: CLK: GPIO18, FS: GPIO19, DIN: GPIO20, DOUT: GPIO21 - **GPIO**: - **PCIe**: - **USB**: - **HDMI**: - **CSI**: - **DSI**: - **Ethernet**: ## GPIO Map | Pin | Name | Type | Functions | |-----|------|------|-----------| | GPIO2 | SDA1 — I2C1 Data (physical pin 3) | I2C | i2c, digital-input, digital-output | | GPIO3 | SCL1 — I2C1 Clock (physical pin 5) | I2C | i2c, digital-input, digital-output | | GPIO4 | GPIO4 — General Purpose (physical pin 7) | — | digital-input, digital-output | | GPIO5 | GPIO5 — General Purpose (physical pin 29) | — | digital-input, digital-output | | GPIO6 | GPIO6 — General Purpose (physical pin 31) | — | digital-input, digital-output | | GPIO7 | CE1 — SPI0 Chip Enable 1 (physical pin 26) | SPI | spi, digital-input, digital-output | | GPIO8 | CE0 — SPI0 Chip Enable 0 (physical pin 24) | SPI | spi, digital-input, digital-output | | GPIO9 | MISO — SPI0 MISO (physical pin 21) | SPI | spi, digital-input, digital-output | | GPIO10 | MOSI — SPI0 MOSI (physical pin 19) | SPI | spi, digital-input, digital-output | | GPIO11 | SCK — SPI0 Clock (physical pin 23) | SPI | spi, digital-input, digital-output | | GPIO12 | PWM0 — Hardware PWM (physical pin 32) | — | digital-input, digital-output, pwm | | GPIO13 | PWM1 — Hardware PWM (physical pin 33) | — | digital-input, digital-output, pwm | | GPIO14 | UART0 TX — UART Transmit (physical pin 8) | UART | uart, digital-input, digital-output | | GPIO15 | UART0 RX — UART Receive (physical pin 10) | UART | uart, digital-input, digital-output | | GPIO17 | GPIO17 — General Purpose (physical pin 11) | — | digital-input, digital-output | | GPIO18 | GPIO18 — PCM CLK / PWM0 (physical pin 12) | — | digital-input, digital-output, pwm | | GPIO19 | GPIO19 — PCM FS / PWM1 (physical pin 35) | — | digital-input, digital-output, pwm | | GPIO20 | GPIO20 — PCM DIN (physical pin 38) | — | digital-input, digital-output | | GPIO21 | GPIO21 — PCM DOUT (physical pin 40) | — | digital-input, digital-output | | GPIO22 | GPIO22 — General Purpose (physical pin 15) | — | digital-input, digital-output | | GPIO23 | GPIO23 — General Purpose (physical pin 16) | — | digital-input, digital-output | | GPIO24 | GPIO24 — General Purpose (physical pin 18) | — | digital-input, digital-output | | GPIO25 | GPIO25 — General Purpose (physical pin 22) | — | digital-input, digital-output | | GPIO26 | GPIO26 — General Purpose (physical pin 37) | — | digital-input, digital-output | | GPIO27 | GPIO27 — General Purpose (physical pin 13) | — | digital-input, digital-output | ## Available Software - **[raspberry-pi-os]()** (open-source) - **[ubuntu]()** (open-source) - **[home-assistant-os]()** (open-source) ## Description ## 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. ## Where to Buy - [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4787&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) — 35 ## Resources - [product page](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4787&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) - [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F4787&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) - [documentation](https://openhardware.directory/r?to=https%3A%2F%2Fwww.raspberrypi.com%2Fproducts%2Fcompute-module-4%2F%3FresellerType%3Dhome&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) - [datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fcdn-shop.adafruit.com%2Fproduct-files%2F4787%2F4787_cm4io-datasheet.pdf&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) - [github](https://openhardware.directory/r?to=https%3A%2F%2Fgithub.com%2Fraspberrypi&ref=openhardware.directory&product=raspberry-pi-cm4-io-board&source=md-export) ## Tags `raspberry-pi`, `cm4`, `io-board`, `carrier-board`, `pcie`, `hdmi`, `gigabit-ethernet`, `hat` ## Images ![Raspberry Pi CM4 IO Board](https://nbg1.your-objectstorage.com/openhardware-directory/entities/raspberry-pi-cm4-io-board/28e880d67729.jpg) ![Raspberry Pi CM4 IO Board](https://nbg1.your-objectstorage.com/openhardware-directory/entities/raspberry-pi-cm4-io-board/be400ec5bc55.jpg) --- [View full device page](https://openhardware.directory/devices/raspberry-pi-cm4-io-board)