How Can I Check Signal Strength of the EC20 Module Using the Linux Terminal?

AvatarByBarbara Hernandez Linux OS Management

When working with cellular modules like the EC20 on a Linux platform, understanding and monitoring signal strength is crucial for ensuring reliable connectivity and optimal performance. Whether you’re deploying IoT devices, managing remote communication systems, or simply troubleshooting network issues, having quick access to signal metrics directly from the Linux terminal can save time and enhance your workflow. This capability empowers users to make informed decisions about placement, configuration, and network diagnostics without relying on graphical interfaces or external tools.

The EC20 module, known for its robust LTE capabilities, integrates seamlessly with Linux systems, offering a range of commands and utilities to interact with the modem. Checking signal strength through the terminal not only provides real-time feedback but also allows for automation and scripting, which is invaluable in large-scale or embedded deployments. By leveraging native Linux commands and modem-specific interfaces, users can gain insights into signal quality, network status, and connection stability.

In the following sections, we will explore the fundamental approaches to accessing signal strength information for the EC20 module within a Linux environment. This overview will prepare you to dive deeper into practical methods, command-line tools, and best practices to effectively monitor and troubleshoot your cellular connection from the terminal.

Using AT Commands to Query Signal Strength

The Quectel EC20 module supports a range of AT commands that can be used to query its status and signal strength directly from the Linux terminal. These commands communicate with the module via a serial interface, typically accessed through device nodes such as `/dev/ttyUSB2` or `/dev/ttyUSB3`. Before sending AT commands, ensure you have appropriate permissions to access the serial device and that no other process is currently using it.

To check signal strength, the primary AT command is `AT+CSQ`. This command returns the received signal strength indication (RSSI) and channel bit error rate (BER). The RSSI value is a numeric representation of signal quality, where higher values indicate better signal strength.

Example command and response:
“`
AT+CSQ
+CSQ: 15,99
“`

  • The first number (`15`) represents the RSSI.
  • The second number (`99`) indicates the BER, often 99 if unavailable.

The RSSI values correspond to signal strength as outlined below:

RSSI Value Signal Strength (dBm) Description
0 < -113 Very weak/no signal
1 -111 Extremely poor
2 to 30 -109 to -53 Weak to strong signal
31 > -51 Excellent signal
99 N/A Not known or not detectable

To send AT commands from the terminal, utilities like `minicom`, `screen`, or `echo` combined with `cat` can be used. For example, using `echo` and `cat`:

“`bash
echo -e “AT+CSQ\r” > /dev/ttyUSB2
cat /dev/ttyUSB2
“`

However, this approach may require careful handling of timing and terminal settings. Tools like `minicom` provide a more interactive interface.

Other useful AT commands for signal and network information include:

  • `AT+CREG?` — Network registration status
  • `AT+CGREG?` — GPRS network registration status
  • `AT+QENG=”servingcell”` — Detailed serving cell information, including signal quality metrics

Using `AT+QENG=”servingcell”` yields comprehensive details such as RSRP, RSRQ, RSSI, and SINR, which are valuable for LTE signal analysis. Sample response snippet:

“`
+QENG: “servingcell”,”NOCONN”,”LTE”,310,260,1234,5678,67,-95,-10,-5,20
“`

Where:

  • `-95` dBm is RSRP (Reference Signal Received Power)
  • `-10` dB is RSRQ (Reference Signal Received Quality)
  • `-5` dBm is RSSI (Received Signal Strength Indicator)
  • `20` dB is SINR (Signal to Interference plus Noise Ratio)

These metrics provide a detailed view beyond the basic `AT+CSQ` command.

Using Linux Network Tools to Monitor Signal Strength

In addition to AT commands, Linux provides native tools that can extract signal strength information when the EC20 module is configured as a network interface. Typically, the EC20 exposes interfaces such as `wwan0` or `usb0` when using network drivers.

The `mmcli` utility (part of ModemManager) is one of the most effective tools for querying modem status, including signal quality. To use it, ensure ModemManager is installed and running.

Common commands include:

  • `mmcli -m 0` — Shows detailed modem information, including signal quality.
  • `mmcli -m 0 –signal-get` — Retrieves current signal strength metrics.

Example output snippet:

“`
signal quality: 75% (recent)
rssi: -70 dBm
rsrq: -10 dB
rsrp: -95 dBm
snr: 20 dB
“`

Alternatively, `iwconfig` can be used if the device supports wireless extensions, though it is more common for WiFi devices rather than cellular modems.

For systems using `qmi_wwan` drivers, the `qmicli` tool can query signal strength:

“`bash
qmicli -d /dev/cdc-wdm0 –nas-get-signal-info
“`

This command returns detailed cellular signal metrics such as RSSI, RSRP, RSRQ, and SINR.

When using `ifconfig` or `ip link`, basic interface statistics are shown but do not include signal strength. Therefore, relying on modem-specific utilities or AT commands is generally necessary.

Automating Signal Strength Checks in Scripts

For continuous monitoring or integration into diagnostics scripts, automating signal strength retrieval is essential. Below is a simple example of a bash script snippet that sends an AT command and parses the RSSI value:

“`bash
!/bin/bash

DEVICE=”/dev/ttyUSB2″

Send AT+CSQ command and capture response
response=$(echo -e “AT+CSQ\r” > $DEVICE && sleep 1 && cat $DEVICE)

Extract RSSI using grep and sed
rssi=$(echo “$response” | grep “+CSQ:” | sed -n ‘s/.*+CSQ: \([0-

Checking Signal Strength of the EC20 Module via Linux Terminal

The Quectel EC20 is a popular LTE module that supports AT commands for managing network connections and retrieving modem status information. To check the signal strength on a Linux system using the terminal, you typically communicate with the EC20 module through a serial interface or a modem manager utility.

Here are the primary methods to obtain signal strength readings:

  • Using AT Commands via Serial Interface
  • Using ModemManager CLI tools

Using AT Commands to Query Signal Strength

The EC20 module responds to standard AT commands over a serial device, often accessible at `/dev/ttyUSB2` or a similar device node depending on the system setup.

Follow these steps:

  1. Identify the modem device node:
    • Use dmesg | grep ttyUSB or ls /dev/ttyUSB* to find the relevant device.
  2. Open a terminal session with the modem using minicom, screen, or picocom. For example: 
    sudo minicom -D /dev/ttyUSB2 -b 115200
  3. Send the AT command to query signal quality: 
    AT+CSQ
  4. Interpret the response.

AT+CSQ returns the signal quality with the format:

+CSQ: ,
Parameter Description Range
rssi Received Signal Strength Indication 0 to 31 (or 99 if unknown)
ber Bit Error Rate 0 to 7 (or 99 if unknown)

The rssi value can be converted approximately to dBm using the formula:

Signal Strength (dBm) ≈ -113 + (rssi * 2)

For example, an rssi of 15 corresponds to about -83 dBm.

Extended Signal Information Using AT+CESQ

For LTE modules like EC20, the extended signal quality command AT+CESQ provides more detailed metrics:

AT+CESQ

Response format:

+CESQ: ,,,,,
Parameter Description Range
rxlev Received signal level 0-63, 99 = not known
ber Bit error rate 0-7, 99 = not known
rscp Received signal code power 0-96, 255 = not known
ecno Energy per chip over noise 0-49, 255 = not known
rsrq Reference signal received quality 0-34, 255 = not known
rsrp Reference signal received power 0-97, 255 = not known

These parameters are particularly useful for LTE network quality assessment.

Using ModemManager CLI (mmcli) to Check Signal Strength

If your Linux system uses ModemManager to manage cellular modems, you can query signal strength more conveniently without manually sending AT commands.

Steps:

  1. Identify the modem: 
    mmcli -L
  2. Query modem status, including signal quality: 
    mmcli -m

Look for the signal quality section in the output, which typically includes RSSI and other metrics.

Practical Tips for Reliable Signal Readings

  • Ensure the EC20 module is properly registered on the network before querying signal strength; use AT+CREG? or Expert Perspectives on Checking Signal Strength for EC20 Modules via Linux Terminal

    Dr. Elena Martinez (Embedded Systems Engineer, Wireless Communications Lab). When working with the EC20 module on a Linux system, the most reliable method to check signal strength is by utilizing the `mmcli` command from ModemManager. Executing `mmcli -m 0 –signal-get` provides detailed RSSI and RSRP values, which are critical for assessing LTE signal quality directly from the terminal without additional software layers.

    Rajiv Patel (Senior Linux Network Administrator, Telco Solutions Inc.). In my experience, leveraging the `qmicli` tool is essential for Qualcomm-based modules like the EC20. Running `qmicli -d /dev/cdc-wdm0 –nas-get-signal-info` yields comprehensive signal metrics including RSSI, RSRQ, and SINR. This approach is efficient for scripting and automation within Linux environments, enabling continuous monitoring of signal strength for deployment scenarios.

    Lisa Chen (IoT Solutions Architect, Embedded Wireless Technologies). For developers integrating the EC20 module, using AT commands via a serial interface in the Linux terminal remains a straightforward method. Sending the command `AT+CSQ` returns the signal quality in a simple numeric format, which can be parsed easily in scripts. This technique is particularly useful when ModemManager or qmicli are not installed or when low-level control is required.

    Frequently Asked Questions (FAQs)

    How can I check the signal strength of the EC20 module in a Linux terminal?
    You can check the signal strength by using the `mmcli` command-line tool. Run `mmcli -m 0` to display detailed modem information, including signal quality under the “signal quality” section.

    Is there a specific command to monitor real-time signal strength on the EC20 module?
    Yes, you can use `watch -n 1 mmcli -m 0` to refresh the modem status every second, allowing you to monitor signal strength in real-time.

    What prerequisites are needed to use `mmcli` for checking signal strength on the EC20 module?
    Ensure ModemManager is installed and running on your Linux system. The EC20 module must be recognized and managed by ModemManager for `mmcli` commands to work properly.

    Can I use AT commands to check signal strength on the EC20 module via the Linux terminal?
    Yes, by connecting to the EC20 module’s serial interface (e.g., `/dev/ttyUSB2`) using a terminal program like `minicom` or `screen`, you can send the `AT+CSQ` command to retrieve signal quality information.

    What does the signal strength value returned by `AT+CSQ` represent?
    The `AT+CSQ` command returns two values: signal strength (0–31) and bit error rate. A higher signal strength value indicates better signal quality, with 31 being the maximum.

    How do I identify the correct modem index for `mmcli` when multiple modems are present?
    Use `mmcli -L` to list all modems and their indexes. Identify the EC20 module from the list and use its corresponding index with `mmcli -m ` to check signal strength.
    Checking the signal strength of an EC20 module in a Linux terminal involves using specific command-line tools and AT commands tailored for cellular modems. Commonly, users interact with the module via a serial interface, employing tools such as `minicom` or `screen` to send AT commands directly. The AT command `AT+CSQ` is typically used to retrieve the signal quality, returning values that correspond to the received signal strength indication (RSSI) and bit error rate (BER). Understanding how to interpret these values is essential for accurately assessing the module’s connectivity status.

    Additionally, Linux utilities like `mmcli` (ModemManager command-line interface) can provide detailed information about the modem’s signal strength and network status when the EC20 module is managed through ModemManager. This approach offers a more integrated and user-friendly method to monitor signal parameters without manually sending AT commands. Combining these methods allows for flexible and precise monitoring of the EC20 module’s signal strength directly from the Linux terminal.

    In summary, effectively checking signal strength on an EC20 module within a Linux environment requires familiarity with both AT command protocols and Linux modem management tools. Mastery of these techniques enables users to diagnose connectivity issues, optimize network performance, and

    Author Profile

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    Barbara Hernandez
    Barbara Hernandez is the brain behind A Girl Among Geeks a coding blog born from stubborn bugs, midnight learning, and a refusal to quit. With zero formal training and a browser full of error messages, she taught herself everything from loops to Linux. Her mission? Make tech less intimidating, one real answer at a time.

    Barbara writes for the self-taught, the stuck, and the silently frustrated offering code clarity without the condescension. What started as her personal survival guide is now a go-to space for learners who just want to understand what the docs forgot to mention.