2013 C4S/CM4 4G Router EN
Keywords
Raspberry Pi, CM4 Core board, CM5 Core board, 4G LTE, Gigabit Ethernet, USB2.0, Soft Router, RPiOS, Ubuntu OS, OpenWrt
I. Introduction
C4S扩展板是一款基于树莓派CM4核心板设计的4G LTE路由器，板载千兆以太网和USB口，可以运行OpenWrt系统，4G做WAN，千兆以太网做LAN。
扩展板通过USB Type-C口5V3A供电，同时引出一路标准HDMI接口。4G LTE在树莓派OS、Ubuntu OS和Openwt系统下均免驱，即插即用，自动识别。
此扩展板同时也支持树莓派CM5核心板的所有版本。
II. Hardware Spec
1) 1*native Gigabit Ethernet port with an integrated transformer for enhanced electromagnetic performance.
2) 3*USB 2.0 Type-A ports.
3) 1*4G CAT4 LTE.
4) 1*Nano SIM slot.
5) 1*IPEX 1 connector for connecting 4G antenna.
6) 1*standard HDMI port (supports up to 4K resolution).
7) 1*TF card slot, used only for OS storage on CM4 core modules without eMMC.
8) 1*BOOT pin, 2.54mm 2-pin, for flashing OS to eMMC of core boards.
9) Power supply: 5V3A, USB Type-C, which also serves as the OS flashing port.
10) Size: 68*70mm.
11) Full aluminum alloy case.
12) PCB materials certified with UL and RoHS.
| CAT4 4G | |
| BAND | LTE FDD：B1/3/5/8
LTE TDD：B34/38/39/40/41 |
III. Flash OS
It was tested using Raspberry Pi OS, Ubuntu OS, and OpenWrt.
For core boards with eMMC, the OS is flashed onto the eMMC. For core boards without eMMC, the OS is flashed onto the TF card.
Using a core board with eMMC, the hardware operations are as follows:
Connect the USB Type-C port to the computer, and use a jumper cap to short the BOOT pins on the board:
For the flashing method, please refer to:
After the OS flashing is completed, remove the jumper cap and power on again to start the OS.
IV. Work with Raspberry Pi OS
The version of Raspberry Pi OS is: 2025-05-13-raspios-bookworm-arm64.img.xz.
You can download it in:
https://www.raspberrypi.com/software/operating-systems/#raspberry-pi-os-64-bit
4.1 USB port test
Onboard there are three USB 2.0 Type-A ports, connected to a wireless keyboard and mouse, a USB flash drive, and a USB card reader respectively, along with an additional USB 2.0 to CAT4 4G conversion interface.
Execute the commands lsusb and lsusb -t in the terminal. The output is as follows:
Bus 001 Device 003: CAT4 4G.
Bus 001 Device 004: USB2.0-A port (Wireless keyboard and mouse).
Bus 001 Device 005: USB2.0-A port (USB flash drive).
Bus 001 Device 006: USB2.0-A port (USB card reader).
USB devices are detected normally. No device number will appear if no external USB device is connected.
Bus 01 is a USB 2.0 interface with 480Mbps, and the operating mode is also normal.
4.2 Network test
4.2.1 Gigabit Ethernet test
Connect the Gigabit Ethernet to the upstream router. Execute ifconfig -a on the terminal. The displayed eth0 is the Gigabit Ethernet, while eth1 is the CAT4 4G:
We use the network speed testing tool iperf3 for speed tests.
Download iperf3 for Windows:
http://www.mcuzone.com/down/Software.asp?ID=10000634
Install iperf3 on Linux:
sudo apt-get install iperf3
Client mode is around 941Mbps:
Server mode is around 946Mbps:
Note: Gigabit Ethernet speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
4.2.2 4G LTE test
When executing the route command in the terminal, you can see that eth1 is listed first, which means the default internet connection is currently through CAT4 4G:
We pinged both the IP and the domain, and both were successful, indicating that the CAT4 4G is functioning properly:
If you need to operate 4G AT commands, please refer to the following link:
AT command operations for 4G modules
V. Work with Ubuntu OS
The version of Ubuntu OS is: ubuntu-25.04-preinstalled-desktop-arm64+raspi.img.xz.
You can download it in:
https://ubuntu.com/download/raspberry-pi
5.1 USB port test
Onboard there are three USB 2.0 Type-A ports, connected to a wireless keyboard and mouse, a USB flash drive, and a USB card reader respectively, along with an additional USB 2.0 to CAT4 4G conversion interface.
Execute the commands lsusb in the terminal. The output is as follows:
Bus 001 Device 003: CAT4 4G.
Bus 001 Device 004: USB2.0-A port (Wireless keyboard and mouse).
Bus 001 Device 005: USB2.0-A port (USB flash drive).
Bus 001 Device 006: USB2.0-A port (USB card reader).
USB devices are detected normally. No device number will appear if no external USB device is connected.
Execute the commands lsusb -t in the terminal. The output is as follows:
Bus 001 is a USB 2.0 interface with 480Mbps, and the operating mode is also normal.
5.2 Network test
5.2.1 Gigabit Ethernet test
In the Ubuntu OS, the net-tools software needs to be installed. The procedure is as follows:
Execute in the terminal:
sudo apt install net-tools
Connect the Gigabit Ethernet to the upstream router. Execute ifconfig -a on the terminal. The displayed eth0 is the Gigabit Ethernet, while network adapter starting with "enx" indicate 4G LTE:
We use the network speed testing tool iperf3 for speed tests.
Download iperf3 for Windows:
http://www.mcuzone.com/down/Software.asp?ID=10000634
Install iperf3 on Linux:
sudo apt-get install iperf3
Client mode is around 941Mbps:
Server mode is around 946Mbps:
Note: Gigabit Ethernet speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
5.2.2 4G LTE test
When executing the route command in the terminal, you can see that enx000c29a39b6d is listed first, which means the default internet connection is currently through CAT4 4G:
We pinged both the IP and the domain, and both were successful, indicating that the CAT4 4G is functioning properly:
The method for executing AT commands for CAT4 4G on Ubuntu OS is the same as on Raspberry Pi OS.
VI. Work with OpenWrt
The OpenWrt is compiled by our company, and the version is: openwrt-bcm27xx-bcm2711-rpi-4-squashfs-sysupgrade-linux-6.6.73-20250324-7925.img.gz
The C4S expansion board can be configured with Gigabit Ethernet as LAN and CAT4 4G as WAN.
6.1 Preparation
OpenWrt defaults to using the Gigabit Ethernet of the expansion board as the LAN. Connect the Gigabit Ethernet to the PC, go to Windows Settings, find Network & Internet, and open the connected network under Ethernet to view the default gateway IP address. This address is the access address for the OpenWrt's configuration page. As shown in the figure, the tested address in this article is 192.168.1.1.
Then open a web browser, enter 192.168.1.1 to access the OpenWrt. The default username is root, and the default password is password:
6.2 Configure 4G module as WAN
Click on "Services - Terminal," then log in to the terminal. The default username is root, and the password is password:
Execute ifconfig -a, and the result is as follows:
Here, eth1 is for 4G but has not obtained an IP address, which is normal.
Click "Network - Interfaces" - "Add new interface...":
Configure as shown in the figure, where the "Name" can be customized, and then click the "Create Interface" button:
In the "Firewall Settings", set "Create / Assign firewall-zone" to "wan", then click "Save":
Save and return to the previous page, then click "Save & Apply":
So we have configured the 4G as a WAN port. Wait a moment, and you will see the extended the 4G obtain an IP address:
Then we go back to the terminal and execute ifconfig -a, and the result is as follows:
You can see that eth1 has obtained an IP address.
We pinged both the IP and the domain, and both were successful, indicating that the CAT4 4G is functioning properly:
At this point, the properties of the PC network card connected to the Gigabit Ethernet (LAN port) of the C4S expansion board show internet connectivity:
Therefore, the PC can access the internet. At this point, we have completed the setup of the soft router.
VII. The compatibility test of the CM5 core board
▶ Raspberry Pi OS and Ubuntu OS:
The version of Raspberry Pi OS is: 2025-05-13-raspios-bookworm-arm64.img.xz
The version of Ubuntu OS is: ubuntu-25.10-preinstalled-desktop-arm64+raspi.img.xz
| Boot | Supports all versions of the CM5 core board. | |||
| Device Name | HDMI output | USB2.0-A ports | 4G LTE | Gigabit Ethernet |
| Compatible or not? | √ | √ | √ | √ |
| Note: √ = compatible, × = incompatible. | ||||
Note: The version ubuntu-25.04-preinstalled-desktop-arm64+raspi.img.xz fails to boot or crashes when opening software on the CM5 compute module.
▶ OpenWrt:
The OpenWrt is compiled by our company, and the version is: openwrt-bcm27xx-bcm2712-rpi-5-squashfs-sysupgrade-lean-linux-6.12.43-qmodem-20250828.img.gz
| Boot | Supports all versions of the CM5 core board. | |
| Device Name | 4G LTE | Gigabit Ethernet |
| Compatible or not? | √ | √ |
| Note: √ = compatible, × = incompatible. | ||
Note: In the config.txt file of the CM5's OpenWrt, change dtoverlay=dwc2,dr_mode=peripheral to dtoverlay=dwc2,dr_mode=host, otherwise the 4G module on this expansion board will not be recognized.
▶ Test date: October 20, 2025.
Contact Us
QQ：8204136
Email: mcuzone@vip.qq.com
Tel: +86(0)13957118045
If there are any omissions, errors, or infringements on this page, please contact us through the above methods. Thank you!
Copyright 2004-2025 Wildchip