Serial Port Terminal: Communication, Logging, and Debugging for RS-232 / RS-485 and VT-100

Last updated on Dec 6, 2025 by Oliver Reed

SerialTool is a professional, cross-platform software (Windows, macOS, and Linux) designed for testing, debugging, and advanced analysis of serial ports connected to electronic, industrial, and embedded devices. It is currently the most complete solution for serial communication, offering both low-level (byte-oriented) and Advanced Terminal (VT-100) modes.

If you need to connect to a device via a serial port, SerialTool is the indispensable tool: it allows you to monitor, log, debug, and analyze communication professionally.

Wikipedia Insights: Serial port · RS-232 · RS-485 · UART

Full Support for VT-100 Terminal

SerialTool supports VT-100 emulation, which is widely used in professional and infrastructural devices. In these contexts, the Serial Terminal is often the only reliable "service" access channel, remaining available even when the network is down.

In the world of embedded electronics, using a Terminal for firmware debugging is fundamental. If you use platforms such as Arduino, ESP32, STM32, or Raspberry Pi, SerialTool is the ideal tool for monitoring output and system logs.

Difference between Serial Software and Serial Terminal

Common serial port software simply transmits and receives raw bytes via TX (transmission), RX (reception), and ground (GND). In this case, the data stream is not interpreted as a text interface: it is merely displayed "as is".

• ASCII (printable characters)
• Hexadecimal (byte-per-byte analysis)
• Binary (when a bit-level view is needed)

A VT-100 Terminal, on the other hand, must also interpret ANSI escape sequences (ESC) to correctly manage the cursor, colors, screen clearing, and formatting. Here, printing bytes is not enough: emulation is required.

A significant practical difference between the two types of Terminals is, for example, the creation of a new line on the screen.
In a VT-100 Terminal, by convention, a new line is inserted upon receiving the byte sequence 0x0D 0x0A, which tells the Terminal it is time to add a new row to the display.
This standard is not necessarily respected in the case of proprietary serial protocols.
In the industrial Modbus communication protocol, since data is raw and not intended for ASCII display, packets do not end with a specific sequence.
For this reason, SerialTool allows you to set a new line in the Classic Terminal upon packet arrival by using the selectable "Packet Mode" option shown in the following screenshot.

By doing this, upon receiving a sequence of bytes from a specific serial port, the Terminal will generate a new line when the packet is finished.
To determine when a packet is finished, it is important to set the "Last Byte Timeout" in the screen for the serial port in use (typically 50ms).

Note: If you intend to use the VT-100 Terminal mode mentioned below, incoming traffic does not have a specific timeout and depends on the master device you are connected to.
For this reason, to maintain fluid visualization, it is important to set the "Last Byte Timeout" to 1ms. In this case, every incoming stream of bytes is immediately sent for interpretation to the VT-100 Terminal.
Nothing happens if the timeout remains at 50ms, but there is a risk of seeing some animations slowed down or not matching the effect intended by the developer.
An example is the simulation of a progress bar with ANSI characters, which would be rendered incorrectly on screen if the timeout were excessively high.
These examples are small adjustments that require some experience, but SerialTool has been specifically designed to make every type of serial port operation possible. You are therefore given the opportunity to go as far as analyzing individual bytes and evaluating various timings at which the serial port operates.

SerialTool and Low-level Debugging (Byte-oriented)

With SerialTool, it is possible to monitor, log, and debug serial traffic at a low level using the Classic Terminal, displaying the real bytes in transit. Visualization can be in ASCII, Hexadecimal, or combined (ASCII + HEX).

Example: Modbus Protocol

A typical case is Modbus, where Master and Slave devices communicate with strict frames, often over RS-485. In this scenario, a "pure" terminal (VT-100 only) is not ideal: you need to see and verify exact bytes, including CRC and response times.

01 03 00 00 00 02 C4 0B

In classic mode, SerialTool makes frame analysis, address/function verification, and byte-per-byte analysis immediate.

VT-100 Terminal: Advanced Human-Machine Interaction (ANSI/ESC)

When a device provides user-friendly interaction (menus, shells, tables, highlighting), a VT-100 Terminal is often used: data is typically readable ASCII, enriched by ESC sequences. These sequences normally start with the ESC character (0x1B) and command "graphical" actions.

Examples of ANSI/ESC Sequences

• \x1B[2J: Clears the entire screen.
• \x1B[H: Moves the cursor to the top-left (Home).
• \x1B[31m: Changes text color to red.
• \x1B[5;10H: Moves the cursor to specific coordinates (Row 5, Column 10).

In this mode, SerialTool does not just show bytes: it interprets the sequences and shows the user a clean, colored, and navigable interface, as intended by VT-100/ANSI standards.

Comparative Analysis: Modbus (Low-level) vs VT-100 Console

To understand the utility of having both modes in the same software, consider two opposite scenarios:

Legacy software like PuTTY or Tera Term were created almost exclusively for Terminal emulation and are therefore not ideal for byte-oriented debugging of protocols like Modbus. SerialTool combines the best of both worlds.

ESP32 Boot Visualization

To better understand how the same data is visualized differently based on the SerialTool configuration chosen, let's analyze the boot of an ESP32-S3 module via the debug port.
In various screens, the same standard boot sequence (common to many master devices) is repeated, which is ideal for visualization with a VT-100 Terminal.
For comparison, the same sequence is shown using SerialTool's Classic Terminal and also the Hexadecimal Terminal.

First, select the Terminal mode from the main menu as shown in the following image.

Select VT-100 Terminal mode from the Terminal settings.

Once VT-100 Serial Terminal mode is selected, options related to SerialTool's Classic Terminal will be disabled.
By resetting the ESP32 module, we observe the incoming bootloader traffic from the module.

At this point, let's try the same ESP32 module boot procedure with visualization through SerialTool's Classic Terminal.
First, select Classic Terminal mode and select byte representation in ASCII format.
Options related to SerialTool's Classic Terminal will reappear.

By resetting the ESP32 module, we observe the incoming bootloader traffic from the module.

Let's perform the same experiment using hexadecimal traffic visualization by setting the data display mode to hexadecimal.

By resetting the ESP32 module, we observe the incoming bootloader traffic from the module.

As a final test, let's use the other type of SerialTool serial terminal, namely the pure Hexadecimal Terminal.
In this representation, serial port traffic is displayed on the same screen as both hexadecimal and ASCII in two different sections.
This type of visualization is very suitable when you need to clearly see traffic in bytes (inbound and outbound) at the same time.
The choice to use the Hexadecimal Terminal is typically oriented towards developers in embedded environments.

First, select the Hexadecimal Terminal from the main screen.

By resetting the ESP32 module, we observe the incoming bootloader traffic from the module via the Hexadecimal Terminal.

Why Choose SerialTool

SerialTool is the best serial port software because it integrates into a single solution the low-level Classic Terminal and full VT-100 emulation, along with advanced logging and analysis tools.

• Open multiple serial ports simultaneously.
• Instantly switch from byte-per-byte view (ASCII/HEX/BIN) to VT-100 mode.
• Perform advanced logging and data integrity analysis (CRC/checksum, response times).
• Use a single application on Windows, macOS, and Linux for embedded, industrial, and enterprise infrastructure.

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Useful Wikipedia links: Serial port · RS-232 · RS-485 · UART · VT-100 · ANSI escape code · Modbus