5003 CM5 Router EN
Keywords
Raspberry Pi, CM5 Core board, WAN, LAN, Gigabit Ethernet, 5G, 4G, RPiOS, Ubuntu, USB3.0, Router, Switch, RTC, PWM, DSI, CSI, HDMI, OTG
I. Introduction
The CM5 Router Expansion Board is an extension board based on the Raspberry Pi CM5 core board, designed for multi-Ethernet-port applications. The expansion board features one 5G interface and reserves two CM4 4G LTE interfaces (supporting up to three built-in 4G modules in addition to 5G. If M.2 4G is used, this board can accommodate four built-in 4G LTE modules in total).
It features one native Gigabit Ethernet port, four Gigabit Ethernet ports expanded via a switch chip, one USB 3.0, four USB 2.0, one RTC, along with standard Raspberry Pi interfaces like CSI/DSI, HDMI, and a 40Pin GPIO.
The power supply of the CM5 Router extension board adopts a USB-C port, supporting both PD and QC power delivery, with PD handshake at 12V. The expansion board has an onboard 12V to 5V conversion circuit, so if the PD input is 12V3A, it can supply power to the expansion board at 5V5A or above. If only performing some routine operations and the total system current does not exceed 3A, you can also use the 5V3A USB-C OTG port for power (in this case, 5G will be unavailable). Use either of the two ports, but not both simultaneously.
The four Gigabit ports have independent IP addresses but reside on the same subnet, with the address pool being assigned by the upstream router. Any one of these four Gigabit ports can be connected to the upstream router to provide network access for the remaining three ports. If the upstream router is not connected, the Raspberry Pi OS and Ubuntu OS will not be able to obtain a valid IP address (they will be assigned a 169.254.xx.xx IP address, indicating only a physical Ethernet connection but no valid IP address).
II. Hardware Spec
1) 1*USB3.0 to M.2 B-KEY interface for 5G module (30*52mm), also compatible with 4G modules.
2) 1*Nano SIM card slot circuit with 4 onboard SMA antenna connectors.
3) 1*native Gigabit Ethernet port.
4) 4*Gigabit Ethernet ports, expanded via the RTL8111 chip over PCIe, and further extended using a switch chip.
5) 1*USB3.0-A HOST；
6) 4*USB2.0 HOST, including 2*USB-A ports and 2*1.25mm-4P connectors, which can be used for internal 4G expansion.
7) 1*standard HDMI port with 4K output support.
8) 1*RTC, 1.25mm-2P.
9) 1*CSI/DSI0 combo interface, 0.5mm-22P；
10) 4*LEDs: Power indicator LED, Raspberry Pi CM5 power indicator LED, ACT LED and 5G network registration LED.
11) 2*buttons: one is the power on/off button; the other is a 4-port Gigabit Ethernet switch reset button, designed for situations where a valid IP address cannot be obtained after inserting the network cable when the device has been powered on for some time.
12) 40PIN GPIO, 2.54mm-2*20P. Fully compatible with Raspberry Pi 5 pins.
13) 1*TF card slot, used for OS booting on CM5 core boards without eMMC (Version R1.2 does not support booting the OS from a TF card).
14) 1*BOOT jumper for flashing the CM5 core board with eMMC.
15) 1*OTG jumper.
16) 1*USB-C OTG port, serving as the OS flashing port for the eMMC core board. This port can also be used for 5V/3A power supply.
17) Power supply: USB-C port, supports PD and QC, handshakes at 12V.
18) Size: 111*135mm.
19) Optional aluminum alloy casing, sizes: 128*138 (155 with bracket) *31mm
(Description of the 4 Gigabit Ethernet reset port button: Press and release this button to reset these 4 Gigabit Ethernet ports. If the reset fails (i.e., the network fails to renew the IP), hold the button for over 5 seconds and release only when the network icon indicates disconnection.)
III. Flash OS
▶ We use the Raspberry Pi OS, the OS version is 2024-11-19-raspios-bookworm-arm64.img.xz.
You can download it in:
https://www.raspberrypi.com/software/operating-systems/#raspberry-pi-os-64-bit
For core boards with eMMC, the OS is flashed onto the eMMC. If the core board does not have eMMC, the OS is flashed onto the TF card or NVMe SSD (Note: Version R1.2 only supports core boards with eMMC).
Use a core board with eMMC. Before flashing the OS, please connect the power USB-C OTG port to the computer and short the BOOT jumper on the board:
Once the flashing process is complete, remove the two shorting cap, then power on again to start the OS.
For the flashing method, please refer to:
IV. Work with Raspberry Pi OS
4.1 Test USB ports
4.1.1 USB port detection test
Plug the USB device into the USB port of the expansion board, execute the command lsusb in the terminal:
The device identification is all normal.
Note: If there are no external devices connected to the USB ports, the corresponding device numbers will not appear—only the USB hub will be shown. The entry "Bus 005 Device 006" appears here because a wireless keyboard and mouse are connected. If no devices were connected, this number would not be displayed.
Then execute lsusb -t to check if the USB port's working mode is normal:
Bus 02: USB 3.0 port, 5000M.
Bus 04: USB 3.0 port, 5000M.
Bus 05: USB 2.0 port, 480M.
4.1.2 Testing USB3.0 read/write speed:
Insert a USB hard drive enclosure into the USB 3.0-A port of the expansion board, boot the OS, and copy a large file between this hard drive and the eMMC. The file is a single ZIP file with a size of 4.22 GB (33.75 Gb). The test results are as follows:
| Data transfer direction | Time(s) | Transmission speed |
| SSD->eMMC | 35.50s | 0.95Gbps |
| eMMC->SSD | 23.18s | 1.46Gbps |
Note: The read/write speed of the USB 3.0 port is affected by various factors such as SSD quality, interface status, and file storage conditions on the SSD. The above test results are for reference only and do not serve as final parameters for the actual product.
4.2 Ethernet port test
4.2.1 Ethernet port detection test
Connect the native Gigabit Ethernet port to the upstream router, then use any one of the four Gigabit Ethernet ports to link to the upstream router.
Then execute ifconfig -a in the terminal, and the result is as follows:
4.2.2 Ethernet port speed test
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
▶ Test the speed of the native Gigabit Ethernet port:
Client mode is around 936Mbps:
Server mode is around 948Mbps:
Note: Network speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
▶ Test the speed of four Gigabit Ethernet ports:
Connect any two of the four Gigabit Ethernet ports to a PC and an upstream router respectively, then use iperf3 to test the speed between the expansion board's Ethernet port and the PC's Ethernet port:
The Gigabit Ethernet port reaches about 939Mbps when in client mode:
The Gigabit Ethernet port reaches about 947Mbps when in server mode:
Note: Network speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
▶ Test the speed of four Gigabit Ethernet ports by connecting them to downstream devices:
Connect as shown below:
Both the PC and the Raspberry Pi 5 can obtain IP addresses assigned by the upstream router through their Ethernet ports to access the internet.
Use iperf3 to test the speed between the PC and the Raspberry Pi 5.
Using Raspberry Pi 5 as the client and a PC as the server, the speed reaches around 937Mbps:
Using a PC as the client and Raspberry Pi 5 as the server, the speed reaches around 948Mbps:
Note: Network speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
4.3 5G module test
The 5G module provided by our company comes pre-configured out of the factory. Under the official Raspberry Pi OS, it is driver-free and dial-up-free, with auto-identification and plug-and-play functionality. If the user purchases the 5G module themselves, they will need to configure it on their own; otherwise, it cannot be used directly.
This document uses the RM520N-GL module as an example for testing.
4.3.1 5G module detection test
We connect the native Gigabit Ethernet port and any of the four Gigabit Ethernet ports into the upstream router, connect the built-in WiFi of the CM5 core board to the upstream router, install the 5G module, and insert the SIM card:
Then execute ifconfig -a in the terminal, and the result is as follows:
Now, eth0 (native Gigabit port), eth1 (4-port Gigabit interface), usb0 (RM520N-GL 5G module), and wlan0 (CM5's built-in WiFi) have all successfully acquired IP addresses.
Execute the route command to view the routing table. Now usb0 is ranked first (with the smallest Metric value), the OS defaults to 5G priority, meaning the internet connection is currently through the 5G module.
Now we can successfully ping both the IP and domain, confirming the 5G module is working correctly:
Open https://www.speedtest.cn/ to run a speed test, with the following results:
Note: Network speed tests are affected by the network environment and testing methods. Please refer to the actual speed, as this test is for reference only.
4.3.2 Modification of Network Priority
Last section, we examined the routing table. The OS defaults to using the 5G network for internet access.
If you don’t want to use 5G for internet access and prefer to prioritize other networks (such as the native Gigabit Ethernet port, the 4-port Gigabit Ethernet, or the built-in WiFi on the CM5 core board), you can execute the command:
sudo ip route del default && sudo route add -net default netmask 0.0.0.0 gw 192.168.8.1
Explanation of these two commands (separated by '&&'):
sudo ip route del default: Remove the default route from the routing table.
sudo route add -net default netmask 0.0.0.0 gw 192.168.8.1: Add the gateway of the upstream router as a new default route (ensure to use the actual gateway address).
After completing the execution, execute the route command to view the routing table. The current default route is the gateway of the upstream router (Rank eth1 first by Metric value):
This way, the network will default to using the upstream router. If you need to switch back to defaulting to the 5G network, please restart the OS.
Note: After a reboot, the routing table resets. To ensure the network continues to use the upstream router as the default route post-restart, you'll need to execute sudo ip route del default && sudo route add -net default netmask 0.0.0.0 gw 192.168.8.1 again.
If you need to customize metric values, that is, to arbitrarily adjust the priority of each network connection, you will need to install the ifmetric software:
sudo apt install ifmetric
After the installation is complete, you can modify the metric value of the network card. For example, the original routing table was displayed as follows:
Now if we want wlan0 to be the first in the routing table, we can execute:
sudo ifmetric wlan0 99
99 is the metric value, which can be customized as long as it remains the smallest among all metric values in the routing table.
After the execution is completed, execute the route command to view the routing table. The current default route is the gateway of the wireless network wlan0, meaning the wireless network card takes the first priority:
This will set wireless network as the default internet connection.
Note: After a reboot, the routing table resets. To ensure the network continues to use the wireless network as the default route post-restart, you'll need to execute ssudo ifmetric wlan0 99 again.
4.5.3 AT command operation
Use lsusb to check the USB devices. The part marked with a red box is the 5G module:
Record the ID value of the 5G module: 2c7c 0801
Use the following command to open the ttyUSB serial port, where the value after echo is the ID recorded above:
sudo modprobe option
sudo sh -c 'echo 2c7c 0801 > /sys/bus/usb-serial/drivers/option1/new_id'
After executing the above two commands, proceed with ls /dev/ttyUSB*.
You should now see four ttyUSB0-3 devices under dev:
Then open the specific serial port (AT command serial port) using a serial port tool.
Install minicom:
sudo apt-get install minicom
Then open the AT command serial port using minicom:
sudo minicom -D /dev/ttyUSB2
(Note: The choice of which serial port to use should be based on the ability to input and run AT commands after entering this port, ensuring that the display is not garbled and the results do not jump erratically.)
The first time you enter an AT command, there may be no echo. If you then input the command at and press Enter, and it returns "OK," it indicates that everything is working properly. If you need to check the echo, please type the command: ate1, then press Enter. After that, you can continue to type other commands and see the inputs.
Common AT commands:
1. Check the echo:
ate1
The first time you enter an AT command, there may be no echo. If you then input the command at and press Enter, and it returns "OK," it indicates that everything is working properly. If you need to check the echo, please type the command: ate1, then press Enter. After that, you can continue to type other commands and see the inputs.
2. Check if the SIM card is detected:
at+cpin?
Return ready to indicate the card has been recognized, if return error, you need to check the hardware.
3. Check antenna signal quality:
at+QRSRQ
| RSRQ | Coverage
strength level |
Notes |
| RSRQ > -10dB | 1 | The signal strength is excellent, suitable for high-speed data transmission and high-quality voice calls. |
| -10dB ≤ RSRQ ≤ -15dB | 2 | The signal strength is good, suitable for most data transmissions and voice calls. |
| -15dB ≤ RSRQ ≤ -20dB | 3 | The signal strength is fair, suitable for low-speed data transmission and low-quality voice calls. |
| RSRQ < -20dB | 4 | The signal strength is very poor, which may result in slower data transmission speeds or connection drops. |
4. Check network registration status:
at+cops?
Normally, it should return the network supporter's code: 7 or 11, where 7 represents 4G, and 11 represents 5G.
Note: The above command at+QRSRQ should not include a question mark, while the other two commands require a question mark.
5. View the SIM card's IMEI code:
at+cgsn
6. Reset 5G module (Sometimes, if you reinsert the SIM card, hot swapping may not work; in such cases, you can use this reset command to reset the module.):
at+reset
7. Disable radio frequency:
at+cfun=0
Enable radio frequency:
at+cfun=1
The two commands mentioned above can be used in pairs to allow the module to re-register with the network without restarting the 5G module.
4.4 RTC test
The expansion board can be used directly in the Raspberry Pi OS when connected to the RTC battery, as shown below:
After the OS starts, execute the following in the terminal:
ls /dev/r*
You can see the RTC device:
The command to display the current system time is date;
The command to write the system time to the RTC is sudo hwclock -w;
The command to read the system time from the RTC is sudo hwclock -r.
As shown below:
If the RTC battery is correctly connected at this time, the RTC will continue to keep accurate time after power loss. If the RTC battery is not properly connected, the time will reset to the default (January 1, 1970) after power loss.
4.5 PWM fan test
Installing the monitoring tool s-tui:
sudo apt install s-tui
Then, run s-tui in the Raspberry Pi terminal, and you can observe the changes in fan speed in the monitoring window.
If you need to customize the fan speed and operating temperature range, please open the terminal and execute the following commands:
sudo nano /boot/firmware/config.txt
Insert the following lines at the end of the file:
dtparam=cooling_fan=on
dtparam=fan_temp0=50000,fan_temp0_hyst=5000,fan_temp0_speed=255
Among them:
fan_temp0=50000, where 50000 represents the temperature, here it is 50°C.
fan_temp0_hyst=5000, where 5000 denotes the hysteresis temperature, here it is 5°C.
fan_temp0_speed=255, where 255 indicates the fan speed, with the maximum being 255.
You can input multiple temperature ranges and their corresponding fan speeds, with each segment on a separate line, differentiated by unique numbering (e.g., 1., 2., 3., etc.):
dtparam=fan_temp1=36000,fan_temp1_hyst=5000,fan_temp1_speed=128
4.6 DSI test
The official two LCD screens for Raspberry Pi: the 1st-gen LCD has a resolution of 800×480, while the 2nd-gen LCD has a resolution of 1280×720. Both screens require additional power supply.
4.6.1 Testing the Raspberry Pi 1st-Gen LCD Display
Connect the 7-inch screen's cable to the CSI/DSI 0 port on the expansion board, then power up the OS. After the OS starts, open the terminal and execute the following commands.
sudo nano /boot/firmware/config.txt
Insert the following lines at the end of the file:
dtoverlay=vc4-kms-dsi-7inch,dsi0
After saving and restarting the OS, you can use the Raspberry Pi 7-inch touchscreen:
4.6.2 Testing the Raspberry Pi 2nd-Gen LCD Display
Connect the Raspberry Pi 2nd-Gen LCD to CSI/DSI 0, power on the expansion board. Open the terminal and execute the following commands:
sudo nano /boot/firmware/config.txt
Insert the following lines at the end of the file:
dtoverlay=vc4-kms-dsi-ili9881-7inch,dsi0
After saving and restarting the OS, you can use the Raspberry Pi 7-inch touchscreen.
Notes
Note1: If both the HDMI display and the 7-inch touchscreen are connected simultaneously, the 7-inch touchscreen may become the secondary screen. Simply power off the system, disconnect the HDMI display, and restart; the 7-inch touchscreen will then function as the primary display.
Note2: The added command actually enables the second display, meaning a dual-screen setup. Whether the second screen's hardware is installed or not, the system may still recognize it as a dual-display configuration. If you use PrtScn (Print Screen) to take a screenshot, it may capture both screens. In some cases, this could even cause the system to fail to boot. Therefore, if you don’t need this screen, it is recommended to remove or comment out this line in config.txt.
4.7 CSI test
The camera used for testing here is the OV5647, and the port is CSI/DSI 0. Once the OS is running, open the terminal and execute the following commands:
sudo nano /boot/firmware/config.txt
Insert the following lines at the end of the file:
dtoverlay=ov5647,cam0
Configure based on your actual model during use. Save and restart the OS, then you can use the OV5647 camera.
Execute the following command in the terminal after reboot:
ls /dev/video*
You will then see the video0 device listed:
Execute libcamera-hello --camera 0 in the terminal to open the corresponding camera for preview:
If a photo is required, please eexcute:
libcamera-jpeg -o test.jpg
The photos are saved in the /home/mcuzone directory (i.e., the user's home directory). The photo effects are as follows:
4.8 4G module test
4.8.1 Connect 4G module
The onboard USB 1.25mm-4P port can be connected to our company's matching CM4 4G mini module:
In this document, the testing module uses CAT4 4G. When executing lsusb in the terminal, the display is as follows, with the red box indicating the 4G module:
Execute ifconfig -a, and the output is as follows:
eth2 is Cat4 4G and has obtained an IP address.
Execute the route command, and you will see eth2 listed first, thus prioritizing internet access via the 4G network:
Both the IP and domain name are successfully pinged at this stage, confirming that the 4G module is working correctly:
The AT command operation method for the 4G module is the same as that for the 5G module. Please refer to Section 4.3. However, the AT command for checking antenna signal quality is different, which is at+csq. The meaning of the return value is as follows:
Return values between 26 and 31 indicate a good signal, with 31 representing a full signal strength; return values between 20 and 25 indicate a barely acceptable signal; return values below 20 indicate a poor signal or that the antenna might not be connected.
4.8.2 Connect other 4G modules
Our company's Qualcomm 4G/Qualcomm 4G-GPS and NL668-EU/EAU/AM 4G modules are auto-identification as USB devices in the Raspberry Pi OS, just like the 5G modules. The onboard 1.25mm-4p USB port is connected to the 4G module, while the M.2 B-KEY slot remains connected to the RM520N-GL module. The OS will automatically prioritize the order, with 5G taking precedence by default, as shown in the following example:
Execute ifconfig -a, and the output is as follows:
Onboard 1.25mm-4p USB connector for Qualcomm 4G/Qualcomm 4G-GPS and NL668-EU/EAU/AM 4G modules, M.2 B-KEY for ZTE CAT4/ZTE CAT4-EU 4G modules, as shown below:
Execute ifconfig -a, and the output is as follows:
This expansion board can support up to four 4G modules simultaneously, as shown in the following example:
4.8.3 Modify the 4G IP address
If the default 4G IP address assigned at the factory conflicts with the IP address being used by the user, or if there is a need to modify the IP address, you can change the 4G module's IP.
CAT4 4G：
Execute the AT command:
AT+ROUTEIP=<newip>
Note: only addresses in the format of 192.168.x.1 are supported. If you set AT+ROUTEIP=192.168.3.1, the final IP address obtained will be 192.168.3.100. After making the changes, you need to power off and restart the OS.
Query current IP: AT+ROUTEIP?, it returns two values, the first one is the old IP, and the second one is the new IP.
Test command: AT+ROUTEIP=?
Qualcomm 4G/Qualcomm 4G-GPS/NL668-EU/NL668-EAU/NL668-AM, ZTE CAT4 4G:
Set the 4G module's IP to directly obtain a public IP. Please execute the AT command:
Set the IP to public: AT+GTIPPASS=1
Set the IP to private: AT+GTIPPASS=0
Check whether the current IP is a public or private IP: AT+GTIPPASS?
After modifying the IP, a power cycle reboot is required for the changes to take effect.
4.9 Button test
CM5 Router expansion board comes with a button that functions as a power switch. When the device is on, pressing the button once will bring up the shutdown menu:
Press the button again to power off immediately.
Power on by pressing the button once while in the shutdown state (requires power connection).
Note: The power button function requires system-level support. While Raspberry Pi OS and Ubuntu enable it by default, the current OpenWrt version lacks this feature.
V. Work with OpenWrt
The OpenWrt used for testing in this document was compiled by Mcuzone, and the version is: openwrt-bcm27xx-bcm2712-rpi-5-squashfs-sysupgrade-linux-6.6.67-20250105.img.gz。
This document uses the RM520N-GL module as an example. By default, the OS configures the 5G module as the WAN port, while the native Gigabit Ethernet port on the expansion board is configured as the LAN port. The four Gigabit Ethernet ports remain unconfigured.
Additionally, you can also use the iStoreOS.
The version is: istoreos-24.10.1-2025052311-raspberrypi-rpi5-squashfs.img.gz
Download address:
https://fw.koolcenter.com/iStoreOS/rpi5/
5.1 Preparation
Connect the native Gigabit Ethernet to the PC's network port. After the OS boots up, go to Windows Settings, find Network & Internet, and open the connected network under Ethernet to view the default gateway IP address. It is the address for the OpenWrt's configuration page. As shown in the figure, the tested address in this article is 192.168.198.1.
Then open a web browser, enter 192.168.198.1 to access the OpenWrt. The default username is root, and the default password is password:
5.2 Configure the LAN port and wired WAN port
Now we need to configure the four Gigabit Ethernet ports as LAN ports and set the native Gigabit Ethernet port as the WAN port.
Click "Services - Terminal" to log in to the OpenWrt terminal. The username is root, and the password is the OpenWrt's "router password" (default: no password).
Execute ifconfig -a, and the output is as follows:
Click "Network - Interfaces - Devices", then click "Configure..." next to "br-lan":
Set the "Bridge Port" in "Regular Device Options", uncheck "eth0" and check "eth2", then click "Save":
Click "Interfaces" in the top menu:
Click "Add New Interface...":
Set the "Name" to "WAN" (customizable), select "DHCP client" for "Protocol", choose "eth0" for "Device", then click the "Create Interface" button:
In the "Firewall Settings", select the WAN and then click the "SAVE" button:
In this way, we've set the native Gigabit Ethernet port as the WAN port and configured the four Gigabit Ethernet ports as LAN ports, with the 5G module automatically assigned as a WAN port by default.
Click "Save and Apply":
Wait a moment, then connect the native Gigabit port to the upstream router, and connect any of the four Gigabit ports to the PC. After that, reboot the OS.
Log back into the OpenWrt's management page and navigate to "Network - Interfaces":
The LAN port is br-lan, which refers to the 4 Gigabit Ethernet ports (eth2).
The wired WAN port is the native Gigabit Ethernet port (eth0).
The 5G module (eth1) is configured as the WAN port by default.
5.3 Test 5G network
5.3.1 5G network stability test
We tested the stability of the 5G network on the PC by ping www.mcuzone.com a total of 60,925 times, with only one packet lost. The average round-trip time was 47ms, indicating extremely stable results.
5.3.2 5G network speed test
We tested the speed of the 5G network on the PC by opening https://test.ustc.edu.cn/ for a speed test, and the results are as follows:
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