How to use the command 'picocom' (with examples)

Picocom is a minimalistic terminal emulation program designed to provide users with a simple way to communicate over serial ports. It primarily focuses on interfacing with hardware devices, such as embedded systems or routers, through serial lines. The command-line utility allows setting parameters critical for serial communication, such as baud rates, and supports various input/output mappings to streamline text formatting.

Use case 1: Connect to a serial console with a specified baud rate

Code:

picocom /dev/ttyXYZ --baud baud_rate

Motivation:

When interfacing with hardware devices, it is crucial to establish a communication link that matches the requirements of the device you’re connecting to. Serial communication is a method often used for debugging, programming, and communication with embedded systems. Since many hardware devices operate over different baud rates, using picocom with a specified baud rate allows for precise synchronization with the target device. This ensures that data is accurately sent and received, leading to effective communication.

Explanation:

• /dev/ttyXYZ: This placeholder represents the serial port that your device is connected to. You might need to replace ttyXYZ with the actual device name, like ttyUSB0 or ttyS0, depending on your operating system and the port being used.

• --baud baud_rate: This argument sets the baud rate for communication. The baud_rate is an integer reflecting the bits per second that the serial port will use. Common baud rates are 9600, 19200, 38400, 57600, 115200, etc. It ensures that both the host and the connected device understand each other at this specified rate.

Example output:

Upon successful connection, the output in the terminal might display:

picocom v3.1

port is        : /dev/ttyUSB0
flowcontrol    : none
baudrate is    : 9600
parity is      : none
databits are   : 8
stopbits are   : 1
-- snipped additional output --

Terminal ready

This output indicates that a successful connection is established at the specified baud rate, and the terminal emulator is ready for user input and device communication.

Use case 2: Map special characters (e.g., LF to CRLF)

Code:

picocom /dev/ttyXYZ --imap lfcrlf

Motivation:

In serial communications, different systems might interpret newline characters differently, which can result in display issues or miscommunication. For instance, Unix-based systems typically use Line Feed (LF) for newlines, while Windows systems use a combination of Carriage Return and Line Feed (CRLF). When dealing with hardware devices, there’s often a need to ensure compatibility with these newline conventions. By mapping LF to CRLF, picocom can ensure that communication is seamless and that data returns to the appropriate line and column, preventing data misalignment or unreadable formats.

Explanation:

• /dev/ttyXYZ: As before, this represents the specific device file corresponding to your serial port connection. Adjust this to match your actual device name.

• --imap lfcrlf: This option configures input mapping to transform LF characters into CRLF. Input mapping can be crucial for systems needing specific newline commands to properly parse and display serial data, ensuring compatibility across different systems and devices.

Example output:

After executing this command, when you send a message that contains a line feed (LF), it automatically gets transformed into CRLF, helping the receiving device display the output correctly. For instance, if you typed:

Hello World!

The device receiving this message would interpret it on a new line, thanks to the CRLF mapping you configured with picocom.

Conclusion

Picocom serves as a versatile tool for establishing serial communication, capable of different configurations to adapt to various hardware and software requirements. By learning to specify baud rates for synchronized data transfer and mapping special characters, users can ensure effective communication and data integrity across different platforms. These examples underscore picocom’s utility in engaging with embedded systems and other hardware interfaces through serial connections.