Introduction

The SIM7600X 4G DONGLE is an industrial-grade 4G modem offering up to 150Mbps downlink and 50Mbps uplink speeds. While officially supporting Windows, Linux, and Android, it requires special configuration for macOS. This guide shows how to access the modem’s UART interface to send AT commands, switch to ECM mode for macOS compatibility, and connect it to both a Mac and Beryl AX router.

macOS Detection Issue

When first connecting the SIM7600X to a Mac, you’ll notice:

• ioreg -p IOUSB -w0 -l shows the device is detected
• system_profiler SPUSBDataType lists the modem
• However, no serial device appears in /dev/ directory (no /dev/cu.usbserial-XXXXXXXX or similar device node is created)

Two issues must be addressed:

1. PIN check must be disabled - This can be done on a Windows/Linux device or via UART
2. USB mode needs changing - The default mode isn’t compatible with macOS

Unlike on Windows/Linux, we can’t send AT commands directly through USB on macOS since the modem isn’t recognized as a serial device. Even with PIN check disabled, if there’s no network service in System Settings, we need to switch the modem to ECM mode using UART access.

UART Connection Options

Option 1: FT232RL USB-to-TTL Adapter

The simplest way to access the UART port is using an FT232RL adapter (available on AliExpress).

Pin Mapping

Connect the FT232RL to the SIM7600X UART port using this mapping:

Important notes:

• Cross-connect RX→TXD and TX→RXD (receiving connects to transmitting)
• The VCC connection is necessary for power when the modem is disconnected from USB
• Only connect VCC after all other connections are secure to avoid power issues
• DTR and CTS pins are not needed for this configuration

Option 2: Flipper Zero GPIO or Raspberry Pi

Another approach is using a Flipper Zero with the UART Terminal app or a Raspberry Pi.

Flipper Zero Setup:

1. Install UART Terminal app on your Flipper Zero
2. Connect to SIM7600X using this pin mapping:

UART Terminal App Features:

• Text or hex mode viewing (hex useful for debugging)
• Direct AT command sending with special keyboard interface
• Configurable baudrate (set to 115200 for SIM7600X)
• Two UART pin configuration options

Important: Do not power your SIM7600X from Flipper Zero’s 3V3 pin (pin 9) as it doesn’t support hot plugging and the modem requires 5V.

Note: Raspberry Pi GPIO pins can also be used in a similar way, connecting the modem’s TXD to Pi’s RXD (GPIO15) and modem’s RXD to Pi’s TXD (GPIO14), then using minicom as the terminal application.

Using AT Commands via UART

Once you’ve established a UART connection using any of the methods above (FT232RL adapter, Flipper Zero, or Raspberry Pi), you need to access the modem through a terminal application.

Setting Up Minicom

1. On macOS, install minicom using Homebrew:

   brew install minicom
   

   Note: On Linux, you would use sudo apt install minicom instead, or try the GUI alternative cutecom with sudo apt install cutecom

2. After connecting the UART adapter, check for the device in /dev/:

   ls /dev/cu.*    # On macOS
   ls /dev/ttyUSB* # On Linux
   

   Look for a device like /dev/cu.usbserial-XXXXXXXX on macOS or /dev/ttyUSB0 on Linux

3. Launch minicom with the correct port and baud rate:

   minicom -D /dev/cu.usbserial-XXXXXXXX -b 115200  # macOS
   minicom -D /dev/ttyUSB0 -b 115200                # Linux
   

   Replace the device path with your actual device path

4. Wait for the modem to initialize completely before sending commands. You may see some startup messages or need to wait 10-15 seconds.

5. To exit minicom when you’re done, press Ctrl+A followed by X, then confirm exit.

Basic AT Command Test

Once connected, test the communication with these commands:

AT

Should respond with OK

AT+CGMI

Should display the manufacturer information

If you receive responses, your UART connection is working correctly and you can proceed to configuring the modem.

Essential AT Commands

Once you’ve established communication with the modem, you can use these AT commands to configure it.

SIM PIN Management

If your SIM card has a PIN code, you’ll need to handle it first (replace “1234” with your actual PIN):

# Enter PIN manually
AT+CPIN="1234"

# Disable PIN check on startup
AT+CLCK="SC",0,"1234"

# Enable PIN check on startup
AT+CLCK="SC",1,"1234"

# Check PIN status (0=disabled, 1=enabled)
AT+CLCK="SC",2

Network Status

Check the modem’s connection to the cellular network:

# Check signal strength (0-31 scale, higher is better)
AT+CSQ

# Current serving cell information and network details
AT+CPSI?

Network Mode

Configure and check the network operating mode:

# Check current network mode (2=Automatic, 38=LTE only)
AT+CNMP?

# Check network registration status
AT+CREG?

# Check data connection registration status (LTE)
AT+CEREG?

IP Connection

Verify the modem’s data connection:

# Check if data connection is active
AT+CGACT?

# Check current assigned IP address
AT+CGPADDR=1

# Get detailed connection info (APN, IP, DNS servers)
AT+CGCONTRDP=1

# Show all configured APN profiles
AT+CGDCONT?

USB Mode Management

Most important for macOS compatibility:

# Check current USB mode
AT+CUSBPIDSWITCH?

# Switch USB mode (format: AT+CUSBPIDSWITCH=<pid>,<enable>,<reboot>)
# Common modes:
# 9011 - RNDIS (best for Windows)
# 9018 - ECM (best for macOS/Linux)
# 9001 - QMI/NDIS
# 9003 - MBIM

# Example: Switch to ECM mode with auto-reboot
AT+CUSBPIDSWITCH=9018,1,1

USB Modes Explained

ECM Mode (9018)

• Ethernet Control Model
• Preferred for: macOS, Linux
• Command: AT+CUSBPIDSWITCH=9018,1,1

RNDIS Mode (9011)

• Remote Network Driver Interface Specification
• Preferred for: Windows
• Command: AT+CUSBPIDSWITCH=9011,1,1

Other modes (MBIM, QMI/NDIS) are present but not useful for macOS users.

Setting Up macOS Connection

After configuring the modem to ECM mode via UART:

1. Disconnect the UART cable from the modem
2. Connect the modem directly to your Mac via USB
3. Wait approximately 30-60 seconds for device recognition
4. If your SIM card is properly configured (PIN disabled, data plan active):

You should see a new network interface appear in System Settings → Network, labeled as “SimTech, Incorporated” with a green “Connected” status.

Connecting to Beryl AX Router (GL-MT3000)

The Beryl AX router treats the SIM7600X modem similarly to an Android phone in tethering mode. Both ECM and RNDIS modes are supported. Simply connect the configured modem to the router’s USB port, and the router should automatically detect and use it for internet access.

Conclusion

With the SIM7600X properly configured in ECM mode, you can now use it as a reliable 4G internet connection on your Mac or Beryl AX router. The configuration only needs to be done once, as the modem will remember its settings between uses.