PeterSerialTerminal - Enhanced Serial Terminal Library for Arduino

An enhanced serial terminal library for Arduino based on ErriezSerialTerminal, featuring command history, tab completion, larger buffers, and a modern interactive command-line experience.

What's New

This enhanced version transforms your Arduino serial terminal into a modern, user-friendly command interface:

Feature	ErriezSerialTerminal	PeterSerialTerminal
Receive buffer size	32 bytes	256 bytes
Max command length	8 characters	12 characters
Command history	No	Yes (up to 20 entries)
Arrow key navigation	No	Yes (Up/Down)
Tab completion	No	Yes
History management API	No	Yes
Backspace handling	Basic	Enhanced (BS + DEL)
Line editing & cursor control	No	Yes
Backward compatible	-	100%

Command History

Navigate through previously entered commands using arrow keys:

• Up Arrow (↑): Recall previous command
• Down Arrow (↓): Move to next command in history

Up to 20 commands are stored (128 bytes each). Duplicate consecutive commands are automatically skipped.

Tab Completion

Press Tab to auto-complete commands:

• Single match: The command is completed automatically
• Multiple matches: All matching commands are displayed
• No match: A bell character is sent to the terminal

Enhanced Terminal Editing

• Improved backspace support (handles both ^H and DEL / ASCII 127)
• Automatic character echoing for terminal programs like PuTTY
• Line clearing and cursor control for seamless editing
• Post-command handler for custom prompts (e.g., > )

Built-in History Management

Programmatic control over command history:

term.showHistory();   // Display all stored commands
term.clearHistory();  // Clear the history buffer
term.addToHistory("command"); // Manually add a command to history

Supported Hardware

Arduino:

• UNO, Nano, Micro
• Pro / Pro Mini
• Mega / Mega2560
• Leonardo

Other platforms:

• Arduino DUE
• ESP8266 / ESP32
• SAMD21
• STM32F1

Quick Start

Installation

1. Download or clone this repository
2. Copy the folder to your Arduino libraries directory
3. Restart the Arduino IDE

Basic Example

#include <PeterSerialTerminal.h>

SerialTerminal term('\r', ' ');

void setup()
{
    Serial.begin(115200);

    term.setSerialEcho(true);
    term.setDefaultHandler(unknownCommand);
    term.setPostCommandHandler(printPrompt);

    term.addCommand("help", cmdHelp);
    term.addCommand("on", cmdLedOn);
    term.addCommand("off", cmdLedOff);

    pinMode(LED_BUILTIN, OUTPUT);
    Serial.println(F("Type 'help' for usage."));
    printPrompt();
}

void loop()
{
    term.readSerial();
}

void printPrompt()
{
    Serial.print(F("> "));
}

void unknownCommand(const char *command)
{
    Serial.print(F("Unknown command: "));
    Serial.println(command);
}

void cmdHelp()
{
    Serial.println(F("Commands: help, on, off"));
}

void cmdLedOn()
{
    Serial.println(F("LED on"));
    digitalWrite(LED_BUILTIN, HIGH);
}

void cmdLedOff()
{
    Serial.println(F("LED off"));
    digitalWrite(LED_BUILTIN, LOW);
}

API Reference

Constructor

SerialTerminal term(newlineChar, delimiterChar);

Parameter	Default	Description
newlineChar	'\n'	Newline character ('\r' or '\n')
delimiterChar	' '	Separator between command and arguments

Command Registration

term.addCommand("cmd", callbackFunction);   // Register a command
term.setDefaultHandler(unknownHandler);      // Handler for unrecognized commands
term.setPostCommandHandler(promptFunction);  // Called after every command

Serial I/O

term.readSerial();     // Process incoming serial data (call in loop())
term.setSerialEcho(true);  // Enable character echoing

Argument Parsing

char *arg = term.getNext();       // Get next space-delimited argument
char *rest = term.getRemaining(); // Get all remaining characters

Buffer & History

term.clearBuffer();     // Clear the serial receive buffer
term.showHistory();     // Print command history to Serial
term.clearHistory();    // Clear all history entries
term.addToHistory("cmd"); // Add a command to history manually

Library Configuration

The following macros in PeterSerialTerminal.h can be adjusted:

Macro	Default	Description
ST_RX_BUFFER_SIZE	256	Serial receive buffer size (bytes)
ST_NUM_COMMAND_CHARS	12	Max characters per command name
ST_MAX_HISTORY_ENTRIES	20	Max number of history entries
ST_HISTORY_ENTRY_SIZE	128	Max length per history entry (bytes)

Examples

Example	Description
ErriezSerialTerminal	Basic usage with command registration and argument parsing
ErriezSerialTerminal_EchoAndCallback	Character echoing, post-command handler, and interactive prompt

Library Dependencies

None.

License

MIT License. See LICENSE for details.

Acknowledgments

This project is based on ErriezSerialTerminal by Erriez. The original library provides an excellent, lightweight foundation for serial command parsing on Arduino. This enhanced version builds upon that solid foundation by adding command history, tab completion, extended buffers, and improved terminal editing — while maintaining full backward compatibility. Many thanks to the Erriez team for their outstanding work on the original library.