WSAL18781 – Compute-Module-4/en

Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.

Summary

The official Raspberry Pi CM4 IO Board serves as a baseboard for the Compute Module 4. It consolidates interfaces on one side and is suitable both for development environments and for integration into end products via HATs and PCIe modules.

Related products at JW Tech

Technical overview

Official Raspberry Pi baseboard, compatible with the Compute Module 4 (CM4).
Interfaces are consolidated on one side; supports standard HATs and PCIe devices.
PCIe Gen 2 x 1 port accepts standard PCIe cards; demonstrated working with NVMe drives via a passive adapter.
PCIe interface does not support MSI-X; typical devices fall back to MSI.
USB 2.0 is disabled by default (power saving); enabling requires adding dtoverlay=dwc2,dr_mode=host to config.txt.
Newer OS images (after Oct 30, 2021) report 'config failed, hub doesn't have any ports! (err -19)' in OTG mode; fix by removing otg_mode=1 and adding the dwc2 overlay.
RTC (PCF85063A) resides on I2C-10 at address 0x51; fan controller (EMC2301) at 0x2f on the same bus.
Extended version only supports 12 V; the fan must be connected before powering on, otherwise the control chip may be damaged.
DSI display: default resolution 800×480; when using the official board, jumper J6 must be closed.
When using a DSI display, HDMI1 has no image output even if no DSI screen is connected; enabling two HDMI outputs requires removing the relevant configuration from config.txt.
CSI cameras: single-port cameras work only on CAM0; CAM1 alone is not possible; dual cameras require both ports simultaneously.
Older systems (Buster/Bullseye): CSI/DSI disabled by default; three I2C devices (I2C-10, I2C-11, I2C-0) are occupied; booting uses dtc compilation of dt-blob files.
Newer systems (Bookworm): camera overlays such as ov9281, imx219, imx477, etc.; test commands libcamera-hello / libcamera-jpeg / libcamera-vid.
All changes to config.txt require a reboot to take effect.

Commands and examples – verify before use:

sudo nano /boot/config.txt
dtparam=i2c_vc=on
dtoverlay=i2c-rtc,pcf85063a,i2c_csi_dsi
#dtparam=audio=on
sudo reboot
sudo hwclock -w
sudo hwclock -s
sudo hwclock --set --date="9/8/2021 16:45:05"
sudo hwclock -r
sudo hwclock --verbose
uname -a
dtoverlay=i2c-fan,emc2301,i2c_csi_dsi,midtemp=45000,maxtemp=65000
i2cdetect -y 10
dtoverlay=vc4-kms-dsi-7inch,dsi0
dtoverlay=vc4-kms-dsi-7inch,dsi1
dtoverlay=ov9281,cam0
dtoverlay=imx219,cam0
libcamera-hello --list-cameras
libcamera-hello -t 0
libcamera-jpeg -o test.jpg

Notes and version constraints

Fan connection only in powered-off state; connecting later may damage the control chip.
RTC battery must be properly connected and voltage-intact, otherwise inaccurate time values.
Camera CAM1 cannot be used alone; single-camera operation only via CAM0.
Using DSI disables HDMI1; to enable dual HDMI outputs, remove the DSI configuration.
Older kernel versions (< 6.1.31) do not support the EMC2301 fan driver.
All configuration changes require a reboot; forgetting this causes features not to work.
I2C address verification with i2cdetect -y 10; valid addresses show 'UU' instead of digits.
Connecting devices while powered on is prohibited; always connect first, then power on.

Source and revision record

Compute-Module-4 - Waveshare Wiki
Source revision: 103660
Captured: 2026-09-01T03:38:51+00:00
SHA-256: 35b65975beb83959b7e50227f13930b21eef00831b90d8170258fe6dc6794daf