microbadge/docs/design.md

Design Document: MicroBadge

Overview

MicroBadge is an interactive embedded application built for the BBC micro:bit v2. It is written in Rust using the Embassy async embedded runtime. The project functions as a conference name badge that acts as a professional and technical icebreaker at events.

The application framework includes:

• A menu system for switching between apps.
• A name scroller for displaying your name or custom message.
• A Snake game for fun and interactivity.
• A NFC business card app for sharing contact info. Still in progress

Goals

• Provide a custom and memorable name badge experience.
• Showcase embedded Rust development using async and no-std.
• Enable fun interactions and sharing via NFC.
• Serve as a technical portfolio piece for conferences, meetings, and interviews.

Architecture

1. Core Framework

• Built on Embassy for asynchronous concurrency.
• Uses hardware abstraction layers (HALs) for GPIO, timers, display, and buttons.
• Implements a lightweight app-switcher system with a menu UI.

2. Applications

Name Scroller

• Scrolls a name or message across the LED matrix.
• Configurable for speed and repeat mode.
• Useful for identifying the wearer at a glance.

Snake Game

• Classic Snake game rendered on the 5x5 LED display.
• Uses Button A and Button B for turning.
• Includes food spawning, score tracking, and difficulty selection.
• Uses PWM for different intensity led lights.

NFC Business Card (WIP)

• Leverages the onboard NFC peripheral.
• Intends to share vCard/contact data over NFC.
• Targeted at mobile phones for quick transfer of contact info

User Interaction

• Navigation is handled via micro:bit's Button A, Button B, and long-press Start gesture
• LED matrix provides visual feedback for game states and menu navigation
• Apps are selected from a simple menu UI
• Snake game is tuned to a slower speed (~4Hz) for usability

Development Environment

• Written entirely in Rust, #![no_std]
• Uses Embassy for async device access and task scheduling
• Debugging output via defmt
• Built and flashed using probe-rs and cargo-embed

Future Improvements

• Finalize NFC vCard transmission
• Add configuration storage via flash memory
• Create a desktop companion app for editing settings
• Support BLE for data sync or configuration

Summary

MicroBadge combines a fun hardware platform with modern Rust development. It serves not only as a name badge but also as a way to demonstrate embedded skills, share contact info, and invite technical discussion at events.