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WSAL21666 – CM4-ETH-RS485-BASE-B/en

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Version vom 6. September 2026, 08:03 Uhr von JWTechPublisher (Diskussion | Beiträge) (Freigegebene technische Dokumentation veröffentlicht; Text-only und noindex)
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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 CM4-ETH-RS485-BASE-B is an expansion board for the Raspberry Pi Compute Module 4. It provides two Ethernet ports (one Gigabit RJ45 and one USB-based 100M Ethernet), four isolated RS485 interfaces, two CSI camera ports, HDMI output, and various configuration options via jumpers and config.txt.

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Technical overview

  • Expansion board for Raspberry Pi Compute Module 4; supports 7–36 V DC power or 5 V via Type-C
  • Four isolated RS485 interfaces with 5.08 mm pitch; mode switching via 0R resistors (full-auto/semi-auto)
  • Two Ethernet ports: ETHERNET0 (Gigabit RJ45) and ETHERNET1 (USB-based 100M Ethernet)
  • Two MIPI CSI camera ports (CAM0/CAM1); single cameras work only on CAM0
  • HDMI0 output supports 4K@30fps
  • RTC connection via I2C (address 0x51, bus i2c-10); requires dtparam=i2c_vc=on in config.txt
  • Fan connector: 4-wire, 5V fans only, PWM control via GPIO18 without speed sensing
  • Encryption chip ATSHA204 present, disabled by default
  • USB2.0 disabled by default; enable via dtoverlay=dwc2,dr_mode=host in config.txt
  • Boot switch: ON = boot over USB Type-C (programming), OFF = boot from eMMC/Micro-SD

Commands and examples – verify before use:  

sudo nano /boot/config.txt
dtoverlay=dwc2,dr_mode=host
sudo nano /boot/config.txt
dtoverlay=uart3
dtoverlay=uart4
dtoverlay=uart5
sudo raspi-config
# Interface Options -> Serial Port -> Yes
dtparam=i2c_vc=on
#dtparam=audio=on
sudo wget https://files.waveshare.com/upload/4/42/PCF85063_code.7z
7z x PCF85063_code.7z -O./
cd PCF85063_code/c
sudo make clean && sudo make -j 8 && sudo ./main
cd python/example
sudo python3 main.py
wget https://files.waveshare.com/upload/d/d1/CM4-ETH-RS485-BASE-B-Example.zip
unzip CM4-ETH-RS485-BASE-B-Example.zip -d ./CM4-ETH-RS485-BASE-B-Example
cd CM4-ETH-RS485-BASE-B-Example/FAN/python
sudo python3 FAN.py
sudo raspivid -t 0 -cs 0
sudo rpi-update

Notes and version constraints

  • Do not plug or unplug devices while powered on, except USB and HDMI
  • Verify fan voltage before connecting – only 5V fans are supported
  • When flashing the image via Type-C, do not connect other devices to ensure stable power
  • CM4 requires 5V/2A during normal operation; otherwise automatic shutdowns or clock throttling may occur
  • Switching RS485 modes requires physically changing the 0R resistors on the back side
  • DSI displays are not available on this board – only HDMI0
  • Single cameras work only on the CAM0 port
  • RTC I2C detection can fail if dtparam=audio=on is blocking it or if dt-blob.bin is faulty

Source and revision record

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