MEG-D Terminal

A responsive, network-based terminal for interacting with MEG-D microcontrollers over a UDP JSON serial bridge.

MEG-D Terminal provides a clean desktop interface for sending commands and observing device output in real time, without requiring a direct serial connection.

---

Overview

MEG-D Terminal bridges a local user interface to remote serial devices through a microcontroller acting as a UDP-to-UART gateway.

User Input -> UDP (JSON) -> MCU -> UART -> Device
Device Output -> UART -> MCU -> UDP (JSON) -> Terminal

The application communicates with the microcontroller over UDP using a structured JSON protocol. The MCU performs routing between network packets and serial devices.

---

Features

• UDP-based communication
• JSON protocol for structured messaging
• Device-targeted serial routing
• Real-time console output
• Local echo with distinct styling
• Responsive UI (non-blocking architecture)
• Automatic endpoint latching
• Packaged executable support (no Python required on target system)

---

Communication Protocol

The terminal communicates with the MEG-D microcontroller using a JSON-over-UDP protocol.

Outbound (Terminal -> MCU)

{
  "type": "serial_tx",
  "device": "SerialLIGHT",
  "data": "$Lb100",
  "seq": 1
}

Fields

• type
  Must be "serial_tx"

• device
  Target serial device on the MCU (e.g. SerialLIGHT, SerialUSB)

• data
  Raw string transmitted directly to the UART

• seq
  Sequence number generated by the client

---

Inbound (MCU -> Terminal)

{
  "type": "serial_rx",
  "device": "SerialLIGHT",
  "data": "OK\\r\\n",
  "seq": 42
}

Behavior

• Only messages matching the selected device are displayed
• data is a JSON-escaped string
• Output is appended directly to the console stream

---

Connection Model

This system uses UDP, so there is no persistent connection. Instead, the MCU tracks the most recent client.

• The client sends an initial packet (empty serial_tx)
• The MCU records the sender’s IP and port
• All responses are sent to that endpoint

Implications

• Only one active client is effectively supported at a time
• The most recent client to send a packet becomes the active console

---

Application Behavior

Sending Data

• User enters text in the input field
• Pressing Enter or Send transmits the text exactly as entered
• No newline characters are automatically added
• Text is wrapped into a serial_tx JSON packet and sent over UDP

Receiving Data

• The application listens on a local UDP port
• Incoming packets are parsed as JSON
• Valid serial_rx messages are displayed in the console

Local Echo

• Sent text is immediately displayed in the console
• Local echo is rendered in a different color from device output

---

Getting Started

Requirements

• Python 3.10+
• Tkinter (included with standard Python on Windows)

---

Run from Source

python megd_terminal.py

---

Packaging (Windows Executable)

Install PyInstaller:

pip install pyinstaller

Build executable:

pyinstaller --windowed --onefile --name "MEG-D Terminal" megd_terminal.py

The output executable will be located in:

dist/

---

Project Structure

MEGD-Terminal/
├── megd_terminal.py
├── README.md
├── requirements.txt
└── assets/

---

Design Notes

• The terminal is stream-oriented, not line-oriented
• The MCU handles all routing between network and serial devices
• The protocol is intentionally minimal and extensible
• No ANSI / VT100 terminal emulation is implemented

---

Future Improvements

• Optional newline modes (CR, LF, CRLF)
• Multi-device tabs or sessions
• Binary-safe transmission mode
• Logging and session recording
• Improved connection diagnostics

---

License

MIT License

Copyright (c) 2026

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND.