How to Use the Command 'setserial' (with Examples)

The setserial command is utilized to read and modify serial port information on Linux systems. This command is notably useful for those who work with serial communication devices, allowing users to manipulate and configure settings like data transfer speed, base addresses, IRQs, and other serial port parameters. The command offers both configuration and diagnostic functions for developers and system administrators managing serial connections.

Use Case 1: Print All Information About a Specific Serial Device

Code:

setserial -a /dev/cuaN

Motivation: Using setserial to print all information about a specific serial device is essential for understanding the configuration and status of a serial port. For instance, developers and system administrators might require comprehensive details to troubleshoot connectivity issues, optimize device performance, or verify current settings.

Explanation:

• -a: This argument stands for “all” and prompts the command to display all available information about the specified device.
• /dev/cuaN: This represents the specific device file associated with the serial port you are querying. The /dev/cuaN is a placeholder, and users should replace N with the appropriate port number for their specific system setup.

Example Output:

/dev/cua0, UART: 16550A, Port: 0x3f8, IRQ: 4, Flags: spd_normal
  Baud base: 115200, close_delay: 50, divisor: 0
  closing_wait: 3000

Use Case 2: Print the Configuration Summary of a Specific Serial Device

Code:

setserial -b device

Motivation: Printing a configuration summary during the bootup process can help in verifying initial settings and configurations of serial devices before they are actively used by applications. This is particularly important for ensuring reliability and consistency in environments where devices depend on specific configurations to function correctly.

Explanation:

• -b: The “brief” option provides a summarized overview of the configuration without the verbose output seen with other options.
• device: This refers to the specific serial device file you wish to review, such as /dev/ttyS0.

Example Output:

/dev/ttyS0, UART: 16550A, Port: 0x3f8, IRQ: 4

Use Case 3: Set a Specific Configuration Parameter to a Device

Code:

sudo setserial device parameter

Motivation: Setting specific configuration parameters allows for customization and optimization of serial ports to meet specific requirements. This can include adjusting baud rates, changing interrupt requests (IRQs), or setting device timeouts, which can enhance performance and compatibility with different hardware or applications.

Explanation:

• sudo: Running the command with superuser privileges is necessary because changing hardware configurations requires elevated permissions.
• setserial: The command being invoked to modify the configuration.
• device: Identifies the target serial device. For example, /dev/ttyS0.
• parameter: The specific setting you wish to adjust, such as irq 3 or baud_base 9600.

Example Output: Upon successfully setting the parameter, there is no output, but you can verify changes with setserial -a device.

Use Case 4: Print the Configuration of a List of Devices

Code:

setserial -g device1 device2 ...

Motivation: Reviewing the configurations of multiple devices at once eases administration and troubleshooting of systems that employ several serial devices. This is particularly useful for checking consistency across devices or when quickly documenting configurations for reports or maintenance logs.

Explanation:

• -g: The “get” flag processes multiple device files and retrieves their configurations.
• device1 device2 ...: This is a list of device files whose configurations you want to print. It allows the command to gather data on multiple serial ports simultaneously, such as /dev/ttyS0 /dev/ttyS1.

Example Output:

/dev/ttyS0, UART: 16550A, Port: 0x3f8, IRQ: 4
/dev/ttyS1, UART: 16550A, Port: 0x2f8, IRQ: 3

Conclusion

The setserial command is a versatile tool for managing serial port configurations on Linux systems, offering detailed inspection and modification capabilities. Whether diagnosing issues with a single port, setting parameters to optimize performance, or gathering data on multiple devices, setserial provides the necessary functions to maintain effective serial communications.