This guide provides troubleshooting recommendations to help users explore Sixfab Base HAT and explains how to interact with it to quickly move through the evaluation and development phases of product design.

Important items to review


To ensure stability, a minimum requirement of 5V / 2A power supply is required to power the device. Any power supply with current capacity of less than 2A may damage the module and/or hardware.
It is recommended to use an official Raspberry Pi power supply.


  • Check the compatibility of SIM with the module from the SIM provider. The compatibility includes the supported region and frequency band information. Also, check the supported bands of the module from the product specification. 
  • Check the SIM card slot for any damaged pin. With a damaged pin, your SIM will not be recognized.
  • Confirm the micro-SIM(3FF size) SIM card is inserted in the right direction.


  • Confirm that the APN(Access Point Name) is correct. If it’s wrong, your device won’t be able to get on the proper cellular network and transfer data. The APN is unique to each vendor and, sometimes, to each different type of SIM card you buy from that vendor such as AT&T SIMs have APNs of & nxtgenphone.
  • Check the authentication type and credentials(username and password) with the SIM provider if required. It could be PAP or CHAP.

Antenna Ports

  • Make sure the right antenna is connected to the right port/interface.
  • Make sure the female u.FL connector of the antenna is connected/snapped firmly to the male u.FL connector of the module.

Power Status of the HAT

Ensure that the HAT has the power to operate. In order to check it see if the POWER LED is lit.

USB Connectivity

From the physical level without any Linux driver, the Linux OS should recognize USB device included Vendor ID (VID), Product ID (PID).

Check all USB devices with lsusb , if the correct vendor ID and product ID are seen, then USB connection is OK. If any of this info is missing there are several possibilities of this missing information. These are:

  • The USB is not connected or the USB cable is damaged.
  • The module is not powered or inserted in the HAT.
[email protected]:~ $ lsusb Bus 001 Device 009: ID 2c7c:0125 Quectel Wireless Solutions Co., Ltd. EC25 LTE modem Bus 001 Device 007: ID 1bc7:1206 Telit Wireless Solutions LE910Cx Bus 001 Device 014: ID 1bc7:1101 Telit Wireless Solutions Telit ME910 Bus 001 Device 005: ID 0424:7800 Standard Microsystems Corp. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Supported USB driver VID, PID list:




Quectel UC20



Quectel EC25



Quectel BG96



Telit LE910Cx



Telit ME910C1-WW



The Sixfab 3G, 4G/LTE Base HAT is the bridge between the mini PCIe module and the Raspberry Pi(or similar host). Hence, the required driver depends on the module. Each module manufacturer provides its driver manual for the supporting operating systems, mainly Linux and Windows.

Applicable Modules and USB Interface Information

ModuleUSB DriversInterfaces

USB Serial OptionttyUSB0 — DIAG
ttyUSB1 — GNSS
ttyUSB2 — AT command
ttyUSB3 — Modem

Device Port Availability

If the operating system recognizes the modem, devices named /dev/ttyUSBx are created. You can check if the ttyUSB(s) are available under the /dev directory. Expected outputs are as follows:

For Quectel:

[email protected]:~ $ ls /dev/ttyUSB* /dev/ttyUSB0  /dev/ttyUSB1  /dev/ttyUSB2  /dev/ttyUSB3

For Telit:

[email protected]:~ $ ls /dev/ttyUSB* /dev/ttyUSB0  /dev/ttyUSB1  /dev/ttyUSB2  /dev/ttyUSB3  /dev/ttyUSB4

If any of the ttyUSB(s) is missing, then check the drivers according to the OEM’s Guides:

UART Connectivity

Both UART and USB can be used to communicate with the module. To check if everything is fine with UART:

AT Commands

The essential details that you will control with AT commands are listed below.

📖 How to send AT Commands to a cellular module?

For full details on sending AT command, please see "Sending AT Commands"

1. Registration

AT+CGREG? and AT+CREG? AT commands returns the registration status of the device.

+CREG: <mode>,<stat>
Possible values are:

0,0 Not registered, ME is not currently searching a new operator to register to
0,1 Registered, home network
0,2 Not registered, but ME is currently searching a new operator to register to
0,3 Registration denied
0,4 Unknown
0,5 Registered, Roaming

2. SIM Card Status

Confirm that the device can recognize the SIM.

AT+CPIN? should return READY.

3. Signal Quality

AT+CSQ AT command returns the signal strength of the device.

+CSQ: <rssi>,<ber>
Possible values are:

<rssi> - received signal strength indication
0 - (-113) dBm or less
1 - (-111) dBm
2..30 - (-109)dBm..(-53)dBm / 2 dBm per step
31 - (-51)dBm or greater
99 - not known or not detectable

<ber> - bit error rate (in percent)
0 - less than 0.2%
1 - 0.2% to 0.4%
2 - 0.4% to 0.8%
3 - 0.8% to 1.6%
4 - 1.6% to 3.2%
5 - 3.2% to 6.4%
6 - 6.4% to 12.8%
7 - more than 12.8%
99 - not known or not detectable

4. PDP Context Set Up

Check the PDP context parameters such as PDP type (IP, IPV6, PPP), APN, data compression, header compression etc. your module is trying to use, with the command: AT+CGDCONT?
Possible responses are:

+CGDCONT: 1,"IPV4V6","vzwinternet","",0,0
+CGDCONT: 2,"IP","super","",0,0
Need Help?

Support Request

Please attempt the solutions recommended in this guide before contacting Support or Community. If these don’t resolve the issues, report your issue in community by answering the form questions below.

Please be as specific as possible. Basically, tell us what steps we need to take to create the issue, what you expected to happen and what actually happened.

  • Describe Your Problem:
  • Use Case Scenario:
  • Environment
    • Raspberry Pi Model / SBC:
    • Operating System (OS):
    • HAT:
    • Antenna:
    • Mini PCIe Module:
    • SIM:
    • Other peripherals, if any:
  • Cellular Connection Type(PPP - QMI - ECM):
  • Service or Script Logs:
  • Outputs of the following Linux commands:
    • cat /etc/os-release
    • uname -a
    • lsusb
    • lsusb -t
    • usb-devices
    • dmesg | grep tty
    • ls -l /sys/bus/usb-serial/devices
    • ls -l /dev/serial/by-id
  • Responses to all AT commands listed below:
  • Quectel Modules Telit Modules
    AT AT
    AT+QCFG=”usbnet” AT#USBCFG?
    AT+QCFG="band" AT#BND?
    AT+QCFG="nwscanseq" AT+GMM
    AT+QCFG="nwscanmode" AT#SWPKGV
    AT+QCFG="iotopmode" AT#FWSWITCH?

AT Commands Manuals List

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