devttyUSB0

/dev/ttyUSB0 is the conventional path to the first USB serial port on many Linux systems. It represents a USB-to-serial adapter as a character device that can be opened and used like a normal serial port by software. The device file is created by the kernel when a USB device that enumerates as a serial interface is connected and bound to an appropriate driver.

The exact behavior depends on the hardware and driver. Common drivers for USB serial devices include ftdi_sio for FTDI chips, cp210x for Silicon Labs CP210x, ch341 for CH341 devices, and pl2303 for Prolific adapters. When a device is recognized, kernel messages (viewable with dmesg) typically indicate the driver bound to the port and may name the port as /dev/ttyUSB0 (or /dev/ttyUSB1, etc. for multiple ports).

Permissions and access: /dev/ttyUSB0 is usually owned by root with a dialout group in many distributions. Non-root users often need to belong to the dialout group or rely on a udev rule that grants access.

Usage: Applications communicate with /dev/ttyUSB0 by configuring standard serial parameters such as baud rate, data bits, parity, and stop bits. Typical tools include screen, minicom, picocom, or libraries that open the device file. For example, configuring a 9600 baud, 8N1 connection can be done with appropriate settings via a serial program or via stty (e.g., stty -F /dev/ttyUSB0 9600 cs8 -cstopb -parenb).

Troubleshooting: If the port does not appear, verify the cable is a true USB-to-serial adapter, check power/connection, review dmesg for driver messages, and confirm the correct driver is loaded. Some devices may expose as /dev/ttyACM0 instead of /dev/ttyUSB0.