Compute Module 4 PoE Board

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Compute Module PoE Board

Compute Module IO Board with PoE Feature, Composite Breakout Board for Developing with Raspberry Pi CM4 / CM4L





This is an IO board for evaluating the Raspberry Pi CM4 or being integrated into end products. the board feature PoE function, it can be used for all variants of CM4.


1. DO NOT hot-plug any devices except the USB and HDMI.
2. Please check the fan voltage before connection, support 5V and 12V. The default connection is 5V and you can modify the FAN_VCC jump cap to switch.
3. Micro USB is used as a USB SLAVE interface to write images, not as an OTG interface.
4. Provide 5V 1.5A for CM4 to ensure that it is in normal use. Otherwise, there may be problems such as automatic shutdown, frequency reduction, and so on.
5. Onboard 4-ch USB 3.2 Gen1 connector by default.
6. When using the POE function, check whether the switch supports PoE for the 802.3af network standard.
7. When POE is required, connect the POE jumper cap to the EN position.
8: Two DISP interfaces cannot be used together by default.


Compute_Module 4 POE Board
Compute_Module 4
Compute Module 4 IO Board 5.png

What's on board


No. Component Description
1 CM4 connector Suitable for all variants of Compute Module 4
2 DC power port 7~36V DC wide range power supply, recommend 24W power adpater at least.
3 Gigabit Ethernet RJ45 with PoE support 10/100M auto-negotiation, for connecting router or switch with PoE function
4 USB SLAVE Interface Writing emmc for Compute Module 4
5 USB3.2 Interface 4 x USB 3.2 Gen1 interface for USB devices.
6 HDMI Interface Dual HDMI ports for dual 4K 30fps output.
7 RTC RTC battery holder.which can be connected to CR2032 battery. The real-time clock can be used to wake up, shut down, or reboot Compute Module 4.
8 CAM 2x MIPI CSI camera connectors.
9 DISP 2x MIPI DSI display connectors.
10 FAN Fan header, support PWM Fan.
11 FAN Power Select 5V or 12V voltage to drive the fan
12 IO-VREF/PoE selection IO-VREF: CM4 IO logic level: 3.3V or 1.8V
PoE: enable (EN) or disable (DIS)
13 40PIN GPIO header For connecting Raspberry Pi HATs
14 CAM0 and DISP0 I2C bus fit the jumpers when using CAM0 or DISP0
15 Misc configurations Special function pins
16 Dual LED indicators red: Raspberry Pi power indicator
green: Raspberry Pi operating status indicator
17 TF card slot (bottom side) Insert a Micro SD card with a pre-burnt system, to start up Compute Module 4 Lite

Special Function Pin Description


Name Description
1 PI BOOT Low level, Pi booted from USB SLAVE port
2 EEPROM WP Low level, prevents EEPROM from being overwritten
3 IP1/0 CM4 board MXL7704 AN1/0 pin
4 VADC COMP Composite video output
5 ETH IN ETH simultaneous signal
6 PI_EN Synchronized with PI_RUN signal
7 PI_GLOBAL_EN CM4 onboard MXL7704 power enable pin, disabled for low level
8 PI_RUN CM4 status indication, high means power on, force pull low to force restart CM4
9 WIFI_EN WIFI enable, low level disable, enabled when not connected
11 BT_EN Bluetooth enable, low disable, enabled when not connected


Do not plug or unplug any device while the base board is powered on.

Writing Image


  • Note: Please connect the fan before turning on the power of the baseboard and then complete the test. Please do not connect the fan after the baseboard is powered on, because the fan control chip has been powered on, otherwise, the chip will be burned!
  • Note: Before connecting, please confirm whether the rated voltage of the fan is consistent with the voltage connected to the fan.

Please note that DSI and CSI are prohibited when using RTC.
I2C-10 is used by default.

RTC (PCF85063a) on i2c-10, address is 0 x 51 (7-bit address)
FAN ( EMC2301 ) on i2c-10, address is 0 x 2f (7-bit address)

If you need to add it to your program instead of the kernel, you can refer to the C and Python demo reference click here


sudo nano /boot/config.txt
 #Add the following lines at the end
 #Add # in front of dtparam=audio=on
 #Save and exit, restart
 sudo reboot

How to use Hwclock

Synchronize system clock to hardware clock:

sudo hwclock -w

Synchronize hardware clock to system clock:

sudo hwclock -s
 #The network or the NTP needs to be closed, otherwise it will be changed back.

Set the hardware clock time:

sudo hwclock --set --date="9/8/2021 16:45:05"

View hardware clock:

sudo hwclock -r

Display version information:

sudo hwclock --verbose


When powered on, the fan will spin for 1 second, then stop for 2 seconds, and then spin again, this is a normal phenomenon
There is no official configuration method for the fan currently, there is a third-party configuration method:
This method is published by a third party, and we are not responsible for any problems!

sudo apt-get install dkms 
mkdir -p ~/src
cd ~/src
git clone
cd cm4io-fan
sudo chmod 777
sudo  ./

#If an error message appears: Your kernel headers for kernel 5.XX.XX-v7l+ cannot be found at
#After rebooting the device, you can execute it:

#The following is the description of config.txt
Name:   cm4io-fan
Info:   Raspberry Pi Compute Module 4 IO Board fan controller
Load:   dtoverlay=cm4io-fan,<param>[=<val>]
Params: minrpm             RPM target for the fan when the SoC is below 
                            mintemp (default 3500)
        maxrpm              RPM target for the fan when the SoC is above
                            maxtemp (default 5500)
        midtemp             Temperature (in millicelcius) at which the fan
                            begins to speed up (default 50000)
        midtemp_hyst        Temperature delta (in millicelcius) below mintemp
                            at which the fan will drop to minrpm (default 2000)
        maxtemp             Temperature (in millicelcius) at which the fan 
                            will be held at maxrpm (default 70000)
        maxtemp_hyst        Temperature delta (in millicelcius) below maxtemp
                            at which the fan begins to slow down (default 2000)

Or directly refer to the following:


The fan will start to accelerate when temperature is higher than 45 degrees Celsius, and will up to the highest speed when higher than 50 degrees Celsius.


Configuration file

CSI and DSI are disabled by default. When using the camera and DSI, it will occupy three I2C devices: I2C-10, I2C-11, and I2C-0.

  • Open a terminal and run the following commands:
sudo apt-get install p7zip-full -y
7z x CM4_dt_blob.7z -O./CM4_dt_blob
sudo chmod 777 -R CM4_dt_blob
cd CM4_dt_blob/
# If using two cameras and DSI1 execute
sudo dtc -I dts -O dtb -o /boot/dt-blob.bin dt-blob-disp1-double_cam.dts
# In the use of any DSI, HDMI1 no image output, even if you do not connect the DSI screen as long as the corresponding file compiled, that HDMI1 no output
# If you need to restore, delete the corresponding dt-blob.bin can be: sudo rm -rf /boot/dt-blob.bin 
#Execution is complete, power off and restart CM4

New Version (Bullseye)

Camera Config

  1. Execute the following commands to edit "/boot/config.txt" file.
    sudo nano /boot/config.txt
  2. Block or remove the automatic camera detection statement:
  3. Add the driver of the camera you are using, here I take IMX219 as an example and connect it to CAM0, and attach the adapter.
  4. Model CAM0 Set Sentence CAM1 Set Sentence
    OV9281 dtoverlay=ov9281,cam0 dtoverlay=ov9281,cam1
    IMX290/IMX327 dtoverlay=imx290,clock-frequency=37125000,cam0 dtoverlay=imx290,clock-frequency=37125000,cam1
    IMX378 dtoverlay=imx378,cam0 dtoverlay=imx378,cam1
    IMX219 dtoverlay=imx219,cam0 dtoverlay=imx219,cam1
    IMX477 dtoverlay=imx477,cam0 dtoverlay=imx477,cam1
    IMX708 dtoverlay=imx708,cam0 dtoverlay=imx708,cam1
    • If you are using the official Raspberry Pi camera and only one camera is connected, there is no need to set the config file.
    • CM4-NANO - only CAM0 is used, so you only need to add "dtoverlay=imx219,cam0".

    5. Ctrl+x to exit the editor.
    6. Reboot the Raspberry Pi.

    sudo reboot

Camera Test

  1. Enter the camera detection command, you can see that the camera is detected by now.
    libcamera-hello --list-cameras


  2. Display the camera screen on the desktop.
  3. libcamera-hello -t
  4. Taking photos.
    libcamera-jpeg -o test.jpg
  5. Record a video of 10s.
    libcamera-vid -t 10000 -o test.h264
  6. Other Commands
    Check whether the camera is detected:
    libcamera-hello --list-cameras

    Open the corresponding cameras:

    libcamera-hello  --camera 1
    libcamera-hello  --camera 0

    Take a photo:

    libcamera-jpeg -o test.jpg
    #Add --camera to specify a camera 

Old Version (Buster)

Camera Config

    1. Execute the following command to enter the Raspberry Pi configuration.
    sudo raspi-config

    2. Choose Interfacing Options and enter.
    3. Choose Camera:
    4. Choose to enable the camera interface.
    5. The system prompts as follows:
    6. Back to the main interface, select Finish.
    7. Reboot the system.

    Camera Test

    raspistill -o image.jpg
    • Test the recording function:
    raspivid -o video.h264 -t 10000
      • Where -t 10000 means recording for 10 seconds, users can adjust according to their own needs.
      • Please refer to CSI.



3D Drawing

Demo codes




a) Check if dtparam -audio -on is blocked in /boot/config.txt.
b) Check if the /boot/dt-blob.bin file exists, if it does, please delete it.



Technical Support

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