RPi Compute Module 4 (CM4) IO Board

Note: This is the IO board for the newly launched Raspberry Pi Compute Module 4.

Note: The Compute Module is not included, please choose your preferred CM4 from here:

• Raspberry Pi Compute Module 4 WITH Wireless - Pick RAM and eMMC Size
• Raspberry Pi Compute Module 4 WITHOUT Wireless - Pick RAM and eMMC Size

Note: Check out these bundles:

RPi CM4 IO Board Bundle for CM4 with eMMC	RPi CM4 IO Board Bundle for CM4 Lite

With the launch of Raspberry Pi 4 Model B (1GB, 2GB, 4GB) last year (2019) and the 8GB RAM version in May this year (2020), everyone has been asking for Compute Module 4. Now, the waiting is over.

Compute Module 4 is official launched on 19th October 2020 with the same or better spec, and there are 32 variants of the module to choose from. Since there are quite significant upgrades on Compute Module 4 compares to its predecessor (CM3 or CM3+), you will need a new IO board for it. This is the IO board designed by the Raspberry Pi team specifically for CM4:

The Raspberry Pi CM4 IO board is designed for the development of products using the Raspberry Pi Compute Module 4. In some situations, the CM4 IO board can be used directly in products. The CM4 IO board contains many of the interfaces that the Raspberry Pi 4B has, for general usage you should refer to Raspberry Pi 4B documentation. The significant difference to a Raspberry Pi 4B is the addition of a PCIe x1 socket. The CM4 IO board can be used as a reference design for examples of how to interface to the Raspberry Pi Compute Module 4.

This CM4 IO board supports all variants of the CM4 board, including the Lite version (without onboard eMMC). The CM4 should be stacked on the CM4 IO board's two connectors:

Two 100-pin high-density sockets for the CM4

After CM4 is stacked on the IO board

CM4 IO board breakouts quite some extra peripheral ports if we compared it with Raspberry Pi 4 Model B:

• 2 x DSI display port - The DSI connectors are 22-way 0.5mm pitch to pitch. These connectors are the same as the existing CMIO board but different from the Raspberry Pi 4 Model B.
• 2 x CSI camera input port - The CSI connectors are 22-way 0.5mm pitch to pitch. These connectors are the same as the existing CMIO board but different from the Raspberry Pi 4 Model B. Now you can get an extra camera input on the CM4 IO board. The CSI connectors are compatible with the Raspberry Pi Zero CSI connector, so the FFC/FPC cable can be utilized for the camera module interface on the CM4 IO board.
  • 15cm Raspberry Pi Zero CSI FFC/FPC cable
  • 30cm Raspberry Pi Zero CSI FFC/FPC cable
• 1 x PCIe Gen 2 socket - Accepts standard computer PCIe cards. Will require a suitable OS driver for the PCIe card. The PCIe interface on Raspberry Pi 4B is used for the USB 3.0 interface via the VLI805 XHCI controller. If you need USB3.0 on CM4 IO, an external XHCI controller is needed.
  • Currently, the CM4 bootloader DOES NOT support NVMe drives.
  • PCIe interface DOES NOT support MSI-X. Typically PCIe devices will fall back to MSI.
• 1 x Cooling Fan connector - Support standard +12VDC cooling fan with PWM drive and tacho output. An EMC2301 controls the fan via I2C.
• 1 x RTC with Coin Cell Socket - A PCF85063AT RTC is able to wake CM4 from the previous shutdown via alarm output. If an alarm goes off during normal operation, the CM4 will be reset. This can be used as a watchdog timer if required.
• 1 x DC Barrel Jack - A DC Barrel Jack with 5.5mm*2.1mm, +12VDC as the main power supply unit. There is a 12V to 5V DC-DC converter to power the CM4. The +12VDC is also fed the +12V PCIe slot, the cooling fan.
• 1 x USB Micro B Slave port - There is a USB Micro B port for CM4 to be updated via rpiboot. When a USB cable is inserted into this port, the USB hub on the CM4 IO board is automatically disabled, the USB 2.0 on CM4 becomes a USB device (slave).
• 1 x MicroSD card socket - This is only meant for CM4 Lite as it does not come with onboard eMMC memory for Operating System and will require external memory to boot. Although the Raspberry Pi 4B has a microSD card socket, the CM4 IO board comes with a push-push type socket :)

Dual DSI and Dual CSI connectors on CM4 IO board

Note: The CSI on the CM4 IO board is compatible with the Raspberry Pi Zero CSI connector, so you can utilize the FFC/FPC cable for Raspberry Pi Zero to interface with the camera module.

Note: However, the DSI port on CM4 IO Board is NOT COMPATIBLE with the FFC cable for RPi Zero.

Note: If you get the CM4 with eMMC, this video and blog post by Jeff Geerling is helpful for you to flash the eMMC with the OS that you want:

Features and Spec:

• Specially designed for CM4 from the Raspberry Pi team
• Accepts the complete range of CM4 modules, all 32 variants:
  • Raspberry Pi Compute Module 4 WITH Wireless - Pick RAM and eMMC Size
  • Raspberry Pi Compute Module 4 WITHOUT Wireless - Pick RAM and eMMC Size
• External +12VDC PSU, through DC Barrel Jack 5.5mm*2.1mm
• 2 x Full-size HDMI 2.0 connectors
• Gigabit Ethernet RJ45 with POE support
• 2 x USB 2.0 Socket, with the header for two more sockets
• USB Micro B socket for updating the CM4's onboard eMMC
• MicroSD Card socket for CM4Lite modules, Push-Push socket
• PCIe Gen 2 x 1 socket
• Standard Cooling Fan connector, support PWM and Tacho feedback
• External power connector ( +5, +12VDC)
• 2 x MIPI DSI display FPC connectors ( 22pin 0.5mm pitch cable)
• 2 x MIPI CSI-2 camera FPC connectors ( 22pin 0.5mm pitch cable)
  • It is compatible with the Raspberry Pi Zero CSI connector, so please get the FFC/FPC cable for Raspberry Pi Zero if you do not have one.
• Raspberry Pi HAT connector, the standard 40-pin GPIO, and the PoE 4-pin header
• RTC with Battery socket and ability to wake up CM4
• Various jumpers to disable features e.g Wireless, EEPROM writing
• Compliance: For a full list of local and regional product approvals, please visit: raspberrypi.org
• Dimension: 160mm x 90mm

• 1 x Raspberry Pi Compute Module 4 IO Board

• CM4 IO Board Product Brief
• CM4 IO board datasheet
• Raspberry Pi Compute Module 4 IO Board KiCAD files, you might need to install the latest nightly build KiCAD version to get the full features on the CM4 IOB KiCAD files.
• How to flash Raspberry Pi OS onto the Compute Module 4 eMMC with usbboot, by Jeff Geerling with video
• Compute Module 4 datasheet
• BCM2711 (Processor SoC) Peripherals
• Raspberry Pi Getting Started by raspberrypi.org
• Raspberry Pi Projects and tutorials