How to turn on and set up USB-Xiaomi Mi 9 modem: Full guide 2026

Connection USB-The Xiaomi Mi 9 modem can be a lifeline when Wi-Fi is unavailable or mobile internet is unstable, but many users face problems: the smartphone does not recognize the modem, does not appear a connection icon or the speed leaves much to be desired. In this article, we will analyze all the nuances - from the choice of compatible equipment to fine-tuning network parameters.

It is important to understand that Xiaomi Mi 9 (codename cepheus) supports the USB-Debugging and working with external modems, but this requires the correct configuration of both the device itself and the modem software. ADB-commands, as well as common errors that interfere with stable connection.

If you have previously tried to connect the modem through OTG-And the cable didn't work out -- don't blame the technology, 80 percent of the time, the problem is the wrong settings. APN, No drivers or operator locks, and our instructions will help you avoid these pitfalls.

1. Which one? USB-Modems compatible with Xiaomi Mi 9

Not everyone. USB-The modem will work with the Xiaomi Mi 9 smartphone:

• 🔌 Support for the standard USB OTG — The modem must be able to work in mode RNDIS or ECM (Ethernet Control Model: Most of the modern Ethernet Control Models 4G-modems (Huawei) E3372, ZTE MF823, Megafon M150-2) Support these protocols.
• 📶 Frequency bands – the modem must support the same frequencies as your operator. For example, for MTS and Beeline in Russia, bands are relevant. B3 (1800 MHz), B7 (2600 MHz), B20 (800 MHz).
• 🔄 Modem firmware – some models (e.g. older versions of Huawei) E8372) Require firmware updates to work correctly with Android 10+.

In our experience, the following models work best with Xiaomi Mi 9:

⚠️ Note: Modems with proprietary protocols (e.g., some Beeline models or Tele2) You may not be defined by the system. Before buying, check the specifications on the manufacturer's website.

2. Preparation of Xiaomi Mi 9 to connect the modem

Before you connect the modem, you need to configure the smartphone itself. Here are the key steps:

1. Turn on OTG mode – go to Settings → Connections and Sharing → USB and activate the USB OTG option. On some firmware, this item may be in Additional Settings → Developer Mode.
2. Activate Developer Mode – if it’s not on the menu, go to Settings → About Phone and click on MIUI Version 7 times.
3. Permission. USB-Debugging - in the developer menu, turn on debugging by USB and confirm the permission at the first connection to the PC.

We also recommend updating the firmware to the latest version. MIUI (at the time of writing the article is relevant MIUI 14 based on Android 12. Older versions (e.g., Android 12, MIUI 11 on Android 10 may not support some protocols USB-modem.

Turn on USB OTG customized|Activate the Developer Mode|Update MIUI last-minute|Permission. USB-debugging|Check availability OTG-cable-->

⚠️ Note: If you use custom firmware (like LineageOS or Pixel Experience), additional kernel customization may be required to support RNDIS. In this case, it is better to refer to the documentation of your firmware.

3. Connection USB-modem: step-by-step instruction

Now, let's get to the connection itself.

• 📱 Xiaomi Mi 9 smartphone with enabled OTG
• 🔗 Quality OTG-cable (better with power if the modem is energy-consuming)
• 📡 Compatible USB-modem SIM-map and positive balance

Step 1. Connect the modem to OTG-cable and then insert the cable into the port USB-C Wait for the new notification to come out. USB-device.

Step 2. Open the notification panel and find the message "USB-device connected. tap it and select Data Transfer (or "RNDIS", if there is such an option).

Step 3. Go to Settings → SIM-maps and mobile networks → Access point (APN). Here we need to add a new one. APN-profile for your operator. You can find the parameters on the provider's website or use universal:

Name: My Internet


APN: internet.beeline.ru (for Beeline) / internet.mts.ru (for MTS)




Proxy: not installed




Port: not installed




User name: not established




Password: not set




Type of authentication: PAP or CHAP




Type APN: default,supl

Step 4: Save the settings and restart the smartphone. Once turned on, check for the 4G or LTE icon in the status bar.

💡

If the modem is not detected, try connecting it to the charger on the 1-2 Some models require a "wake-up" before working in the office. OTG-mode.

Alternative methods of connection (ADB, Termux)

If the standard method doesn’t work, you can try activating the modem via ADB or Termux terminal, which requires technical knowledge but often helps in complex cases.

Method 1: Through ADB

1. Connect your smartphone to your PC and open the command line.
2. Enter a command to check the connected USB-devices: Adb devices
3. Next Post: Adb shell settings put global tether_dun_required 0 This team is shutting down the check. DUN (Dial-Up Networking, which can block the connection.

Method 2: Through Termux

Install Termux from F-Droid and do:

pkg update && pkg install usb-modeswitch


su




usb_modeswitch -v VENDOR_ID -p PRODUCT_ID -M"55534243123456780000000000000011062000000100000000000000000000"

Here. VENDOR_ID and PRODUCT_ID You can learn via lsusb command on Linux PC.

5. Common mistakes and their solutions

Even with the right connection, there can be problems, and let's look at typical scenarios and how to fix them:

⚠️ Warning: If the Xiaomi Mi 9 starts to run out quickly after you connect your modem, check your power saving settings. USB-Add modem to exceptions: Settings → Battery → Energy conservation → Annexes.

Critical information: On firmware MIUI There is a bug below version 12.0.3 that causes a problem. USB-modems with Qualcomm chipset MDM9207 (For example, some models ZTE) They can cause the phone to restart. Update the firmware before use!

6. Optimization of connection speed and stability

To maximize speed and minimize connection breaks, follow these tips:

• 📡 Modem Positioning – Place it to a window or on a hill. USB-Extensioner will help to find the optimal position.
• 🔄 Network mode - in the modem settings (via the web interface on the PC) install LTE Only if 4G-This will prevent you from switching to slow. 3G.
• 🛡️ Turn it off. VPN — some VPN-services conflict with USB-Modems, especially if they use their own DNS.
• 🔋 Power – if the modem supports external power (for example, via MicroUSB), connect it to charging.

To check the real speed, use the Speedtest by Ookla or nPerf app. Pay attention to the Ping parameter – if it is above 100 ms, this may indicate an operator network overload.

💡

For maximum speed, disable automatic app updates and background sync in your Google account settings. This will free up the channel for your main traffic.

7. Safety in the use of USB-modem

USB-modems, like any network device, can be targeted for attacks:

• 🔒 Change the standard password of the modem web interface (usually admin/admin). Use a complex password with numbers and symbols.
• 🌐 Disable remote access in the modem settings if you don't need it. This will prevent unauthorized connection.
• 🛡️ Use firewalls like NetGuard or AFWall+ They will help you to control which programs are available. USB-internet.
• 🔄 Regularly update the modem firmware – manufacturers often release patches for vulnerabilities.

It is also worth noting that some public Wi-Fi networks can block traffic from the Internet. USB-modems (especially when used) SIM-In this case, the change of the card will help. APN or use of proxy.

FAQ: Frequent questions about USB-modems on Xiaomi Mi 9