1003 RPi0 4G Cat1-Hub EN

Keywords

Raspberry Pi Zero, Zero 2W, Cat1 4G LTE, USB2.0, USB Type-C, USB HUB, Nano SIM, RPi-Connect, Remote connection

I. Introduction

The Raspberry Pi Zero series (including the Zero, Zero W/H, and Zero 2W) is a highly cost-effective embedded system platform, known for its small size, low power consumption, and acceptable performance, making it suitable for many lightweight application scenarios. Although the Zero series is compact, it reserves a large number of expansion interfaces. Especially on the backside of the board, gold-plated test points for USB and power are brought out. We can use these sets of USB and power test points to expand various types of peripherals.

This expansion board is essentially a USB hub that connects to the Zero's USB port via pogo pins. It expands four USB ports via USB, with one USB port converted to a 4G Cat1 module, and three USB 2.0-C host ports.

4G Cat1 is a high-cost-performance module aimed at medium-speed IoT applications around 10 Mbps. The 10 Mbps downlink and 5 Mbps uplink speeds can satisfy the majority of connectivity and transmission requirements. The CAT1 module is driver-free and automatically recognized in the Raspberry Pi OS, Ubuntu system, and OpenWrt system, making it easy to use.

(Note: When using this expansion board, the Raspberry Pi Zero development board cannot utilize the OTG function. If you need to use the OTG function, all interfaces on the expansion board will become unavailable.)

II. Hardware Spec

1. This board connects to the Raspberry Pi Zero's USB port and power contacts via four pogo pins for both power supply and communication.

2. A USB-C power port, which functions are the same as the power port on the Raspberry Pi Zero itself. You can choose to use either one, but not both simultaneously.

3. A 4G CAT1 module, can option the GPS functionality. Users in other countries can also select other CAT1 modules that match their frequency bands.

4. A Nano SIM card slot (located on the reverse side). Note: SIM card hot-swapping is not supportted.

5. A 1 GEN IPEX connector, which can be used with external 4G FPC or rod antennas.

6. Three USB 2.0 Type-C host, with each USB port capable of supplying 1A of power (Note: the Raspberry Pi Zero's own OTG functionality will no longer be usable, and the Zero's own micro USB port cannot be used to connect any USB devices, otherwise, this expansion board will not function properly).

7. Have debugging UART and the AT main UART, both with 3.3V voltage levels.

8. Three LEDs:

one is the power indicator for the expansion board.

one is the power indicator for the 4G module.

one is the NET led: a 1.8-second on and 0.2-second off cycle indicates successful network registration, while a 1.8-second off and 0.2-second on cycle indicates that the device has not registered with the network, and you should check the SIM card and antenna.

9. A BOOT button and a reset button.

10. Sizes: 65*30*6.6mm, with four M2.5mm mounting holes.

11. An optional 3D printed base is available to protect the circuit board.

12. The circuit board uses an ENIG (Electroless Nickel Immersion Gold) process, is produced without lead, and the PCB has received UL and RoHS certifications, with a fire protection rating of 94V-0.

Model	CAT1	CAT1-GPS	CAT1-EU	CAT1-EA
Frequency band	TDD：B34/38/39/40/41 FDD：B1/3/5/8		FDD：B1/3/7/8/20/28（A/B）	FDD：B1/3/5/7/8/28（A/B）
GNSS	None	Support GPS L1,BDS B1 frequency band Support Beidou-2/Beidou-3 satellite Support AGPS 64 channels Cold start sensitivity -147dBm Tracking sensitivity -160dBm Horizontal accuracy<2.0m CEP50	None	None
Speed	TDD：MAX 8Mbps（DL）/2Mbps（UL） MAX 6Mbps（DL）/4Mbps（UL） FDD：Max 10Mbps（DL）/5Mbps（UL）		Max 10Mbps（DL）/5Mbps（UL）
Sensitivity	FDD B1:-99dBm（10M) FDD B3:-99dBm（10M) FDD B5:-99dBm（10M) FDD B8:-99dBm（10M) TDD B34:-100dBm（10M) TDD B38:-100dBm（10M) TDD B39:-100dBm（10M) TDD B40:-100dBm（10M) TDD B41:-100dBm（10M)		B1: -99dBm（10M） B3: -99dBm（10M） B5: -99dBm（10M） B7: -97.5dBm（10M） B8: -98dBm（10M） B20: -98dBm（10M） B28: -98dBm（10M）

III. Work with Raspberry Pi OS

Hardware Platform: Raspberry Pi Zero 2 W + Expansion Board, driver-free.

Software Platform: Raspberry Pi OS;used in this document is: 2023-05-03-raspios-bullseye-arm64.img.xz(Raspberry Pi OS with desktop).

(If you are using the RPi Zero/Zero W/Zero WH, they only support 32-bit systems. Please be sure to download the correct version.)

You can download the Raspberry Pi OS in:

https://www.raspberrypi.com/software/operating-systems/#raspberry-pi-os-64-bit

Different versions of Raspberry Pi OS have varying strategies for network management. Based on the 64-bit OS version, the results are as follows:

OS version (64-bit)	Test results
2023-02-21-bullseye	Driver-Free, No Dial-Up Required, Auto-identification, plug and play, automatic internet connection.
2023-05-03-bullseye
2023-12-05-bookworm	Driver-Free, No Dial-Up Required, Auto-identification, but there may be instances of network connection failure, and the OS requires the installation of DNS software.
2024-07-04-bookworm
2024-11-19-bookworm
2025-05-13-bookworm
2025-10-01-trixie

The Raspberry Pi Zero series boards only support 32-bit OS. The test results are as follows:

OS version (32-bit)	Test results
2023-02-21-bullseye	Driver-Free, No Dial-Up Required, Auto-identification, plug and play, automatic internet connection.
2023-05-03-bullseye
2023-12-05-bookworm
2024-07-04-bookworm
2024-11-19-bookworm
2025-05-13-bookworm
2025-10-01-trixie

☆ 3.1 View hardware devices

The Raspberry Pi Zero2 W board is fixed above the expansion board using four screws. Please pay attention to the installation direction and ensure that the pogo pins on the expansion board align with the corresponding contacts on the Zero board. Connect the HDMI cable and power supply, and note that the Zero's micro USB port should not be connected to any devices.

3.1.1 View USB devices

One USB-C port is connected to a wireless keyboard and mouse, while the other two USB-C ports are not in use. Open the terminal in Raspberry Pi OS and enter the commandlsusb, as shown in the image below:

Device 002: External USB Hub;

Device 003: 4G module;

Device 004: USB2.0 Type-C interface(external wireless keyboard and mouse);

If no device is connected to the USB port on the expansion board, only Device 001, Device 002, and Device 003 will appear in lsusb, Device 004 will not be listed.

If the system stop at the Raspberry Pi logo and fails to boot:

or if after booting, the keyboard, mouse, and 4G module cannot be used,

please carefully check whether the pogo pins are aligned with the gold-plated contacts. Additionally, on the PC, open the config.txt file located in the root directory of the TF card to check the USB initialization script.

You need to confirm that the three red-boxed areas in the following image are all configured completely. If not, please manually add the missing parts and save the file:

# otg_mode=1 (It is recommended to comment out as follow)

dtoverlay=dwc2,dr_mode=host (These two areas must be ensured to be included.)

3.1.2 View 4G module

Open the terminal in Raspberry Pi OS and enter the commandifconfig -a, as shown in the image below:

The eth0 as the 4G Cat1 (which has automatically connected, with the default IP address in the above example being 192.168.10.2).

☆ 3.2 Test 4G module

3.2.1 Operations on 4G when the system has not set up WiFi

When the Raspberry Pi OS boots, WiFi is enabled by default, but it is not connected to any access point (meaning no WiFi account and password are set in the system). So when connecting to the internet via the 4G module, we can perform a ping operation:

Ping the IP should correctly display as follows:

Ping the domain name should correctly display as follows:

This indicates that the 4G connection is normal.

Solution for ping domain error:

Some versions of Raspberry Pi OSs can only ping IP addresses, but may encounter network failures when pinging domain names, reporting DNS errors:

This indicates that the DNS server settings for the 4G module are incorrect. Let's modify the DNS server settings:

First, we need to connect to WiFi:

Click on the network icon in the upper right corner and select the AP you want to connect to:

Enter the password (if there is one), and then click "Connect":

After a successful connection, you can obtain the IP address of the router and access the internet normally:

Install the DNS server switching software udhcpc:

sudo apt install udhcpc

After installation, use the following command to switch the DNS server to the 4G module (in this case, eth0 represents the 4G module; the name may differ depending on the software and hardware platform):

sudo udhcpc -i eth0

This way, you achieve normal internet browsing via 4G.

The method of switching DNS servers for 4G internet access will stop working after the system is restarted. If you want the DNS server to automatically switch to the 4G module each time the system starts, you can follow these steps:

Open rc-local service:

sudo systemctl enable --now rc-local

Use the following command to open rc.local:

sudo nano /etc/rc.local

Add the command you want to execute at startup above the line exit 0, and then save the file (in this example, eth0 represents the 4G module, but the name should match the actual interface identified on your system):

sleep 5 && sudo udhcpc -i eth0 && sleep 5 && sudo udhcpc -i eth0 && sleep 5 && sudo udhcpc -i eth0

The sleep command is used to delay the execution of subsequent commands by a certain number of seconds. Since the 4G module needs some time to acquire an IP address, to prevent `udhcpc` from failing, it needs to be executed several times with a delay added between each execution. As a result, the 4G network becomes usable approximately 20 seconds after the system boots up.

3.3.2 Operations on 4G when the system has already been set up WiFi

If your system was previously set up with WiFi, the Raspberry Pi Zero 2W will provide internet access via WiFi when used alone. When you install our expansion board, upon rebooting the system, it will prioritize using the 4G network for internet access. If you want to switch to WiFi, you can follow these steps:

Disable the 4G network connection:

sudo ifconfig eth0 down

Use udhcpc to switch the DNS server to the WiFi's DNS server.

sudo udhcpc -i wlan0

If you later want to switch back to browsing the internet using the 4G network, you can run:

sudo ifconfig eth0 up

sudo ifconfig wlan0 down

sudo udhcpc -i eth0

3.3.3 Access the 4G module via SSH over WiFi

If you want to use the WiFi of the Raspberry Pi Zero to log in to the Raspberry Pi OS via SSH, and then perform 4G operations on the Raspberry Pi, you need to set up the SSH service before flashing the system. For the steps, refer to this guide.

Or, after entering the Raspberry Pi desktop, connect a keyboard and mouse, and then go to:

Raspberry Pi icon on the top left - Preferences - Raspberry Pi Configuration - Interfaces

Enable SSH as shown:

This allows us to use tools like MobaXterm to SSH into the Raspberry Pi over WiFi.

☆ 3.4 Use AT commands and GPS

3.4.1 Use AT commands

Execute commands in the terminal:

lsusb

Record the ID value of the 4G module: 19d1 0001

Use the following command to open the serial port, where the value after echo is the ID recorded above:

sudo modprobe option

sudo sh -c 'echo 19d1 0001 > /sys/bus/usb-serial/drivers/option1/new_id'

After execution is complete, the OS should have three additional devices: ttyACM0, ttyACM1, and ttyACM2. Input ls /dev to view:

Install minicom:

sudo apt-get install minicom

By default, the AT command serial port is ttyACM0.

Open AT Command serial port by minicom:

sudo minicom -D /dev/ttyACM0

(Note: Typically, three ports (ttyACM0 to ttyACM2）will appear. In general, the AT port is ttyACM0 under most OSs. If that doesn't work, you may try other ports such as ttyACM2. If multiple USB-to-serial devices are present, further attempts will be needed until the correct AT port is identified.)

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 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.

2. Check antenna signal quality:

at+csq

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.

3. Check network registration status:

at+cops?

Normally, it should return the network supporter's code: 7, where 7 represents 4G.

Note: The above command at+csq should not include a question mark, while the other two commands require a question mark.

4. View the SIM card's IMEI code:

at+cgsn

5. Reset 4G 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

6. 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 4G module.

3.4.2 GPS Test (only for GPS version)

When using GPS, you need to connect a passive GPS antenna and ensure that the GPS antenna is extended outdoors.

Run minicom and open the ttyACM0 serial port:

sudo minicom -D /dev/ttyACM0

And execute:

AT+CGNSPWR=1 //Open GPS

AT+CGNSAID=31,1,1,1 //Enable location assistance positioning (the command will immediately return OK, and positioning will succeed in about 2-10 seconds based on signal strength).

AT+CGNSURC=1 //Setup automatic reporting of location information

After running successfully, you will be able to see GPS information output from the serial port:

Wait for a moment, and the device will then be able to acquire its location.

IV. Work with Ubuntu OS

Ubuntu system: Ubuntu Server 24.04 LTS. (The Raspberry Pi Zero 2W cannot use the Desktop version due to performance limitations.)

The image is: ubuntu-24.04-preinstalled-server-arm64+raspi.img.xz

You can download the Ubuntu system in:

https://ubuntu.com/download/raspberry-pi

(If using the Raspberry Pi Zero/Zero W/Zero WH, which only supports 32-bit systems, there may not be a suitable Ubuntu Server system available.)

4.1 Edit the initialization script

After flashing Ubuntu Server to the TF card, please open the config.txt file in the root directory of the system partition on your PC to check the USB initialization script. Ubuntu Server initializes the USB twice, and the first initialization does not configure it into host mode. You need to verify if the position indicated by the red box in the following diagram is fully configured. If it is not, please manually add the complete configuration:

dtoverlay=dwc2,dr_mode=host

4.2 Configure the username and password

Insert the TF card into the Zero 2W and boot the system. Upon the first boot, you will be prompted to log in. The username and password are both ubuntu. After logging in successfully, you will be prompted to change the password:

After modifying the password, you will automatically enter the system.

4.3 Configure the network

After the system boots, there is no network available, and setup is required before it can be used.

Note: the system does not integrate the ifconfig tool by default; only the ip command is available.

Execute ip addr to view and record the network interface name:

The second network interface (enx2089846a96ab) is the 4G module.

Then run the following command to open the network interface configuration file:

sudo nano /etc/netplan/50-cloud-init.yaml

Edit the network interface configuration file according to the image below:

Save and exit, then restart.

After restarting, you can connect to the network. Install the net-tools package for convenience:

sudo apt install net-tools

Run ifconfig -a to see that the 4G module has correctly obtained an IP address:

4.4 Test AT commands

Execute command:

ls /dev

You should be able to see three devices named ttyACM0, ttyACM1, and ttyACM2 under the dev directory:

Install minicom:

sudo apt-get install minicom

Open AT Command serial port by minicom:

sudo minicom -D /dev/ttyACM0

(Note: Typically, three ports (ttyACM0 to ttyACM2）will appear. In general, the AT port is ttyACM0 under most OSs. If that doesn't work, you may try other ports such as ttyACM2. If multiple USB-to-serial devices are present, further attempts will be needed until the correct AT port is identified.)

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 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.

2) Check antenna signal quality:

at+csq

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.

3) Check network registration status:

at+cops?

Normally, it should return the network supporter's code: 7, where 7 represents 4G.

Note: The above command at+csq should not include a question mark, while the other two commands require a question mark.

4) View the SIM card's IMEI code:

at+cgsn

5) Reset 4G 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

6) 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 4G module.

V. The use of MMDVM software

Pi-Star is a software designed for digital voice hotspot boards and repeater boards. It can handle various digital modes including DMR, D-STAR, YSF, P25, NXDN, and POCSAG. When used with a Multi-Mode Digital Voice Modem (MMDVM), it also supports cross-mode conversion (interoperability) functionality.

Test platform: RPi0_4G_Cat1-Hub+Zero 2W

Test System: Pi-Star_RPi_V4.2.2_10-Apr-2025

System download link: https://www.pistar.uk/downloads/

5.1 Testing Pi-Star

Flash Pi-Star to the TF card using a flashing tool, then boot the Zero 2W from the TF card.

Under Pi-Star on the RPi0_4G_Cat1-Hub+Zero 2W, the 4G module can be directly recognized. After the OS boots up, log in to the OS (Username: pi-star, Password: raspberry).

Execute lsusb, the part highlighted in the red box is the 4G module:

The 4G module is driver-free and requires no configuration in the Pi-Star. When executing ifconfig -a, it can be seen that the module has obtained an IP address:

The "wlan0" is the wireless network card of the Zero 2W, which has not obtained an IP address, so this wireless network card cannot be used for internet access. If you need to use this wireless network card to access the internet, please manually connect to the wireless AP using the command line.

The "wlan0_ap" refers to a wireless access point automatically generated by the Pi-Star using the Zero 2W's wireless network card. The access point is named "Pi-Star-Setup" and has no password. You can use a computer or mobile phone to connect to this AP, which will place the computer/phone and the Pi-Star on the same local network.

Execute the command route, and you can see that eth0 (the 4G module) is ranked first, indicating that the current default internet access is through the 4G module:

Pinging the public IP and website succeeded, confirming the 4G module is working normally:

If you want to install the software, please upgrade the OS first:

sudo apt update

If after executing the route command, it is found that the default connection is not through eth0 to access the internet, then the udhcpc software needs to be installed.

sudo apt install udhcpc

Then execute:

sudo udhcpc -i eth0

Open the network address of Pi-Star in a browser on a computer that is on the same network segment as Pi-Star to access the backend configuration page (You can connect your computer to the wireless AP named "Pi-Star-Setup".):

5.2 Testing Pi-Star GUI

In the previous section, we introduced how to use a computer on the same network segment as Pi-Star to open the Pi-Star page for configuration and use. Pi-Star also provides a Pi-Star GUI, which can be installed to directly configure and use the Pi-Star page via a display connected to the Raspberry Pi.

5.2.1 Install Pi-Star GUI

Test platform: RPi0_4G_Cat1-Hub+Zero 2W

Test System: Pi-Star_RPi_V4.2.2_10-Apr-2025

Boot up the Pi-Star and execute the following commands in sequence:

▶ Enable disk expansion service:

sudo pistar-expand

▶ Reboot:

sudo reboot

▶ Change the read/write mode:

Note: When installing software, the Raspberry Pi OS's cursor prompt must display "rw" at the beginning. If it shows "ro," please use the following command to switch:

rpi-rw

▶ Download the installation script:

wget http://pistar.uk/downloads/installGUI.sh

▶ Grant execute permissions to the script:

sudo chmod 755 ./installGUI.sh

▶ Install Pi-Star GUI：

./installGUI.sh

During installation, a significant number of software packages need to be downloaded. You can directly use the 4G network for downloading. If the speed seems slow, you may connect an external USB network adapter to download via wired network.

5.2.2 Run Pi-Star GUI

After the Pi-Star GUI installation is complete, the OS will automatically reboot. After rebooting, it will automatically enter the Pi-Star GUI configuration page. First, you need to log in (Username: pi-star, Password: raspberry):

After logging in, proceed to the configuration page:

After completing the configuration, click the "Apply Changes" button of the corresponding configured module, and the configuration will be successful after a short wait.

Then click on "Dashboard" in the top menu bar to enter the software homepage:

5.3 Other Features of the Pi-Star

The method to exit the MMDVM software page is to press Alt+F4 on the external keyboard. After exiting the page, the screen will display a completely black background with only a mouse cursor, which is normal. At this point, clicking the right mouse button will bring up the menu:

Click the first item in the menu: Terminal emulator, to use the terminal:

In the terminal, we can perform network testing and communication troubleshooting tasks as described in Section 5.1.

The second item in the menu: Web browser, which can launch the Chromium browser when clicked:

The third item in the menu: Applications, is a menu for common software and configuration tools in the Raspberry Pi OS:

To return to the MMDVM software page, execute the following command in the terminal:

chromium-browser --noerrdialogs --kiosk --incognito http://localhost

VI. (Remote Connection) RPi-Connect to access your Raspberry Pi remotely

RPi-Connect provides a service for secure access to your Raspberry Pi from anywhere. With this service, combined with the Zero_Cat1_4G Cat1-Hub version, you can still remotely access your Raspberry Pi even when outdoors without a Wi-Fi network. Note: To use this service, Bookworm or a newer system must be running. Additionally, only the Raspberry Pi 5, 4, or 400 can use screen sharing. The Zero 2W can only use Remote Shell. The following demonstrates how to configure the remote connection service.

6.1 Apply for a Raspberry Pi ID

If you already have a Raspberry Pi ID, please log in directly. If not, please follow the steps below to apply.

Open the website at https://id.raspberrypi.com/, and enter the email address and password you wish to use:

After creating the account, you need to verify it by entering your email:

After verification is complete, the ID can be used.

6.2 Install Remote Service

Open the Raspberry Pi terminal and install the Raspberry Pi Connect software:

sudo apt install rpi-connect

After installation, we enter loginctl enable-linger in the terminal to ensure that the remote service is automatically enabled each time the system restarts:

Restart the system. In the graphical interface, select the items in the order shown in the following image to ensure that Raspberry Pi Connect is turned on:

Then enter the following in the Raspberry Pi terminal:

rpi-connect signin

Now, a URL is displayed, as shown in the image above. Open this URL in a browser (it is recommended to use another computer, as the Zero series can be very slow when opening a browser due to hardware limitations).

Click on "Sign in" and follow the prompts to bind the device. First, you need to set the device name:

Click "Create device and sign in":

This completes the binding process, and there will also be a successful message displayed in the terminal:

6.3 Use remote control

On your PC, open: https://connect.raspberrypi.com/devices

The Zero 2W device just added only shows "Remote shell", indicating that this device can only be controlled through a remote command-line interface.

Click on "Connect" to open the remote command-line interface, where you can then enter commands:

VII. Power consumption explanation

RPi0-CAT1 4G	Status	Power consumption
5V power supply	Module standby	0.15A*5V=0.75W
	Speed test (downlink)	0.25A*5V=1.25W
	Speed test (uplink)	0.3A*5V=1.5W

VIII. Expansion board selection guide

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