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WSAL20157 – Compute Module 4 PoE Board (B)/en

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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 Waveshare Compute Module 4 PoE Board (B) is an industrial IO baseboard for the Raspberry Pi Compute Module 4. It provides PoE power supply per IEEE 802.3af, four USB 2.0 ports, two HDMI outputs, RS485/RS232 serial interfaces, an RTC module and fan control. The CM4 itself is not included in the delivery scope.

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Technical overview

  • The board supports all variants of the Compute Module 4 via its MXL socket.
  • Power can be supplied either via PoE (802.3af) or through the USB-C input at 5 V / 2.5 A.
  • Four USB 2.0 ports are present; they are disabled by default and must be enabled in config.txt.
  • Two HDMI outputs support 4K@30fps each; when DSI is active, the second HDMI output is blocked.
  • RS485 features 600 W lightning protection, surge protection and 15 kV ESD protection; an optional 120 Ω balancing resistor is selectable via jumper.
  • RS232 is protected against surge and ESD using a TVS diode.
  • The RTC unit uses a PCF85063ATL on I2C bus 10 at address 0x51.
  • The fan controller EMC2301 is also on I2C-10 at address 0x2f; fan supply voltage is switchable between 5 V and 12 V via the FAN_VCC jumper.
  • A PCIe Gen 2 ×1 slot is available for expansion cards.
  • The micro SD card slot allows booting CM4 Lite variants; the BOOT switch determines whether the system boots from USB-C or from eMMC/SD.

Commands and examples – verify before use:  

sudo nano /boot/firmware/config.txt
dtoverlay=dwc2,dr_mode=host
dtoverlay=uart3
dtoverlay=uart5
sudo nano /boot/config.txt
dtparam=i2c_vc=on
dtoverlay=i2c-rtc,pcf85063a,i2c_csi_dsi
#dtparam=audio=on
sudo hwclock -w
sudo hwclock -s
sudo hwclock --set --date="9/8/2021 16:45:05"
sudo hwclock -r
sudo hwclock --verbose
wget https://files.waveshare.com/upload/7/75/CM4_dt_blob_Source.zip
unzip -o CM4_dt_blob_Source.zip -d ./CM4_dt_blob_Source
sudo chmod 777 -R CM4_dt_blob_Source
cd CM4_dt_blob_Source/
sudo dtc -I dts -O dtb -o /boot/dt-blob.bin dt-blob-disp0-double_cam.dts
sudo dtc -I dts -O dtb -o /boot/dt-blob.bin dt-blob-disp1-double_cam.dts
reboot

Notes and version constraints

  • The CM4 is not included in the delivery scope – it must be procured separately.
  • Activating DSI automatically blocks one of the two HDMI outputs; this applies even if no DSI display is connected.
  • Fan supply voltage must be verified before powering on; plugging in a fan after power-on may destroy the control chip.
  • PoE requires a switch supporting the 802.3af standard; the PoE jumper must be set to EN.
  • When using the USB-C input for flashing, no other power source should be connected simultaneously.
  • Without sufficient power (5 V / 2 A), automatic shutdowns or clock throttling may occur.
  • The third-party fan-control solution (cm4io-fan) is not officially released; Waveshare disclaims responsibility for any issues arising from it.
  • RTC functionality requires disabling DSI and CSI, as both use I2C-10.

Source and revision record

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