Tera Term: A Beginner’s Guide to Serial CommunicationSerial communication remains one of the most reliable and widely used methods for interacting with embedded devices, routers, switch consoles, microcontrollers, and industrial equipment. Tera Term is a free, open-source terminal emulator for Windows that supports serial (COM port) and network (SSH, Telnet) connections, file transfers, and scripting. This guide explains how to set up Tera Term, establish serial communication, configure common settings, use useful features, and troubleshoot frequent problems.
What is Tera Term?
Tera Term is a lightweight terminal emulator originally developed in Japan. It provides:
- Serial (COM port) and network (SSH/Telnet) connections
- Support for common terminal emulations (VT100, VT220, etc.)
- File transfer protocols (XMODEM, YMODEM, ZMODEM)
- A macro language (Tera Term Macro, or TTM) for automation
- Logging, capture, and customizable keyboard mappings
Because it’s free and robust, Tera Term is popular among developers, network engineers, and hobbyists working with serial devices.
Installing Tera Term
- Download the latest Tera Term installer from the official site or a trusted repository. The installer is a standard Windows executable.
- Run the installer and follow the prompts. Default options are fine for most users.
- After installation, launch Tera Term from the Start menu or desktop shortcut.
Note: Run as administrator if you need access to privileged COM ports or to install certain components.
Connecting via Serial (COM) Port
- Identify the device’s COM port:
- Use Device Manager (Windows) > Ports (COM & LPT) to find the COM number assigned to your USB-serial adapter or built-in port.
- Open Tera Term. The initial dialog typically offers to open “Serial” or “TCP/IP.” Choose Serial and select the COM port from the dropdown.
- Click OK to open the connection window.
Common Serial Settings
Serial communication requires matching settings on both ends. The main parameters are:
- Baud rate (bits per second): common values include 9600, 115200
- Data bits: usually 8
- Parity: usually None
- Stop bits: usually 1
- Flow control: options include None, RTS/CTS (hardware), XON/XOFF (software)
To change these in Tera Term:
- Go to Setup > Serial port… and select the desired Baud rate, Data bits, Parity, Stop bits, and Flow control.
- Click OK to apply.
If you get gibberish characters, mismatched baud rate or wrong parity/stop bits are the most common causes.
Terminal Emulation and Character Encoding
- Tera Term supports several emulations (VT100, VT200). For most serial consoles, VT100 or VT220 works well.
- For non-ASCII text or special characters, ensure correct encoding: Setup > Terminal > New-line conversion and Charset settings. UTF-8 may be needed if the device sends Unicode.
File Transfers
Tera Term supports XMODEM, YMODEM, and ZMODEM protocols.
- To receive a file sent from a remote device using ZMODEM, choose File > Transfer > ZMODEM > Receive.
- To send a file to the remote side, choose File > Transfer > ZMODEM > Send and pick the file.
ZMODEM is preferred when available because it supports resume and robust error handling.
Logging and Capture
To save a session:
- File > Log… starts recording received text to a file.
- File > Capture on some versions performs similar capture functions.
Logging is invaluable for recording boot messages, debugging device output, and keeping communication transcripts.
Using Tera Term Macro for Automation
Tera Term Macro (TTM) is a built-in scripting language used to automate repetitive tasks: open ports, send commands, wait for prompts, parse responses, and save logs.
Example simple macro (save as myscript.ttl):
; Open serial port COM3 at 115200 baud setserial 3 115200 8n1 none wait 'login:' sendln 'admin' wait 'Password:' sendln 'mypassword' sendln 'show version' wait '#' logopen 'output.txt' sendln 'show running-config' wait '#' logclose Run via Control > Macro or from Windows Explorer by double-clicking the .ttl file if Tera Term associates macros with the program.
Macros can:
- Automate device provisioning
- Collect logs from many devices in sequence
- Perform firmware uploads combined with file transfer protocols
Keyboard Shortcuts and Useful Features
- Ctrl+Break: Send break signal (useful for interrupting bootloaders).
- Alt+F: Open File menu quickly.
- Setup menu: Save current settings as default (Setup > Save setup).
- Paste: Use right-click or Edit > Paste; in some devices you must respect input timing—use Send and Paste options or macro with paced sending.
Troubleshooting Common Problems
-
No connection / cannot open COM port:
- Ensure no other program (e.g., another terminal) is using the same COM port.
- Check Device Manager for driver issues (reinstall USB-serial drivers if needed).
- Run Tera Term as administrator if access is blocked.
-
Garbled output:
- Mismatched baud rate, parity, or stop bits. Match settings on both ends.
- Wrong character encoding—try different Charset settings.
-
No responses to commands:
- Confirm correct flow control settings.
- Make sure remote device expects carriage return (CR) or line feed (LF) — toggle New-line conversion.
-
File transfer failures:
- Ensure both sides use the same protocol (ZMODEM recommended).
- Some devices require initiating receive before sending.
Security Considerations
- Serial connections are local and not encrypted. Treat consoles as trusted or physically secure interfaces.
- For remote connections Tera Term supports SSH for encrypted terminal access—prefer SSH over Telnet when available.
Alternatives and When to Use Tera Term
Tera Term is ideal for Windows users needing a lightweight, scriptable terminal emulator for serial and SSH/Telnet. Alternatives include PuTTY (popular, smaller feature set), SecureCRT (commercial), and minicom/screen on Linux. Use Tera Term when you want built-in file transfer and a macro language without cost.
Quick Reference Cheat Sheet
- Default serial settings often: 115200 8 N 1 or 9600 8 N 1.
- Flow control: None for basic devices; RTS/CTS for hardware-controlled links.
- To log: File > Log…
- To run macro: Control > Macro or double-click .ttl
Tera Term remains a practical, powerful tool for serial communication and simple network terminal tasks. With the basics above you can connect to devices, automate repetitive interactions, capture logs, and perform file transfers reliably.
Leave a Reply