Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

Adafruit Metro M0 Express - designed for CircuitPython

Overview

Metro is our series of microcontroller boards for use with the Arduino IDE. This new Metro M0 Express board looks a whole lot like our original Metro 328, but with a huge upgrade. Instead of the ATmega328, this Metro features a ATSAMD21G18 chip, an ARM Cortex M0+.

Please note that while this board was our first for CircuitPython usage, better and bigger chips have come out since then! We recommend the Metro M4 for a roomy, speedy, experience.

Specifications

• Processor: ATSAMD21G18 ARM Cortex M0+ @ 48MHz
• Architecture: 32-bit ARM Cortex M0+
• Flash Memory: 256KB
• RAM: 32KB
• SPI Flash: 2MB for CircuitPython storage
• Operating Voltage: 3.3V logic and power
• Input Voltage: 7-9V DC or 5V USB
• Dimensions: 71mm x 53mm / 2.8” x 2.1”
• Height (w/ barrel jack): 13mm / 0.5”
• Weight: 20g

Key Features

ARM Cortex M0+ Processor

• 48MHz Clock: 3x faster than Arduino Uno
• 32-bit Architecture: More efficient processing
• 256KB Flash: 8x more than ATmega328
• 32KB RAM: 16x more than ATmega328
• Low Power: Efficient ARM core

Built-in Storage

• 2MB SPI Flash: External storage chip
• CircuitPython Storage: Files, libraries, and scripts
• Arduino Access: Read/write files from sketches
• USB Access: Appears as USB drive
• Data Logging: Store sensor data and logs

Native USB Support

• Built-in USB: No FTDI chip needed
• Serial Communication: Virtual COM port
• HID Devices: Act as keyboard, mouse, or MIDI
• Mass Storage: Access SPI flash as drive
• Programming: Upload code via USB

Arduino Compatibility

• Arduino IDE: Full Arduino IDE support
• Shield Compatible: Works with most Arduino shields
• Pin Layout: Standard Arduino pin arrangement
• Libraries: Access to Arduino ecosystem
• Familiar Interface: Easy transition from Arduino Uno

Hardware Components

Power Management

• Auto Power Selection: USB or DC input
• 7-9V DC Input: 2.1mm jack with on/off switch
• USB Power: 5V from micro USB connector
• 3.3V Regulator: 500mA peak current output
• Power LEDs: Visual power indicators

User Interface

• 4 Indicator LEDs: Power, RX/TX, and pin 13 LED
• 1 NeoPixel: RGB LED on pin 40
• Reset Button: Manual reset capability
• Rubber Bumpers: Included to prevent sliding

Expansion and Connectivity

• 25 GPIO Pins: 5 more than Metro 328
• Arduino Shield Compatible: Standard shield pinout
• Breadboard Friendly: Easy prototyping
• Mounting Holes: 4 mounting holes for secure attachment

Software Support

CircuitPython

• Primary Platform: Designed for CircuitPython
• Pre-loaded: Comes with CircuitPython installed
• Interactive Development: REPL for real-time coding
• File System: 2MB flash appears as USB drive
• Extensive Libraries: Large CircuitPython ecosystem

Arduino IDE

• Full Support: Complete Arduino IDE compatibility
• Board Package: Adafruit SAMD boards package
• Library Support: Access to Arduino libraries
• Familiar Environment: Standard Arduino workflow
• Easy Migration: Upgrade from Arduino Uno

Development Features

• UF2 Bootloader: Drag-and-drop programming
• Native USB: No drivers needed on most systems
• Serial Monitor: Built-in debugging
• File Access: Read/write SPI flash from code
• Bossa Compatible: Standard ARM programming

Pin Configuration

Digital I/O (25 pins)

• GPIO: All pins can be digital I/O
• PWM: PWM outputs on almost all pins
• Interrupt: External interrupts on most pins
• 3.3V Logic: All pins operate at 3.3V
• Current: 7mA source/sink per pin

Analog Capabilities

• 12 Analog Inputs: 12-bit ADC resolution
• 1 Analog Output: 10-bit DAC on A0
• Reference: Internal or external voltage reference
• High Resolution: 4096 different values (12-bit)
• Multiple Channels: Simultaneous sampling possible

Communication Interfaces

• Hardware Serial: UART on pins 0 and 1
• Hardware I2C: SDA and SCL pins
• Hardware SPI: MOSI, MISO, SCK pins
• Multiple SERCOM: Additional I2C/SPI/UART possible
• USB: Native USB communication

Memory Architecture

Flash Memory (256KB)

• Program Storage: User code and libraries
• Bootloader: UF2 bootloader space
• Large Capacity: 8x more than Arduino Uno
• Fast Access: High-speed program execution

RAM (32KB)

• Variable Storage: Runtime data and buffers
• Large Capacity: 16x more than Arduino Uno
• Fast Access: Zero-wait-state memory
• CircuitPython: Plenty of space for Python objects

SPI Flash (2MB)

• File Storage: CircuitPython files and libraries
• Data Logging: Store sensor data and logs
• User Files: Images, sounds, configuration
• USB Access: Appears as CIRCUITPY drive

Performance Comparison

vs Arduino Uno

• 3x Faster: 48MHz vs 16MHz
• 8x More Flash: 256KB vs 32KB
• 16x More RAM: 32KB vs 2KB
• Native USB: No FTDI chip needed
• More Pins: 25 vs 20 GPIO pins

vs Metro M4

• Slower: 48MHz vs 120MHz
• Less Memory: 256KB vs 512KB Flash, 32KB vs 192KB RAM
• No FPU: No floating point unit
• Simpler: Fewer advanced peripherals
• Lower Cost: More affordable option

Applications

CircuitPython Projects

• Learning Programming: Great for beginners
• Interactive Projects: Sensors and displays
• IoT Devices: Connected projects
• Data Logging: Environmental monitoring
• Educational Tools: STEM education

Arduino Projects

• Upgraded Uno Projects: More memory and speed
• Sensor Networks: Multiple sensor integration
• Communication Projects: Multiple serial ports
• Display Projects: Graphics and animations
• Motor Control: PWM motor control

Professional Use

• Prototyping: Rapid development platform
• Product Development: Bridge to production
• Educational: Teaching embedded systems
• Research: Data collection and analysis
• Art Projects: Interactive installations

Power Specifications

Input Power

• USB Power: 5V from micro USB (500mA max)
• DC Power: 7-9V from 2.1mm jack
• Auto Selection: Automatic power source switching
• Power Switch: On/off control for DC input

Power Consumption

• Active Mode: ~30mA typical operation
• Sleep Modes: Various low-power modes available
• Peripheral Power: Additional current for active peripherals
• USB Power: Can power moderate loads from USB

Getting Started

CircuitPython Setup

1. Connect USB: Board appears as CIRCUITPY drive
2. Edit Files: Modify code.py in any text editor
3. Install Libraries: Copy libraries to lib folder
4. Run Code: Code runs automatically on save
5. Use REPL: Interactive Python shell

Arduino Setup

1. Install Arduino IDE: Download latest version
2. Add Board Package: Install Adafruit SAMD boards
3. Select Board: Choose “Adafruit Metro M0 Express”
4. Install Libraries: Add required libraries
5. Upload Sketches: Program via USB

Package Contents

• 1x Adafruit Metro M0 Express board
• 4x Rubber bumpers
• Documentation and getting started guide
• Pre-loaded CircuitPython firmware

Important Notes

• 3.3V Logic: Not 5V tolerant, use level shifters if needed
• Superseded: Metro M4 recommended for new projects
• Shield Compatibility: Most Arduino shields work with level shifting
• CircuitPython Pre-loaded: Ready to use out of the box
• File System: Don’t edit files while code is running

Advantages

• Easy to Use: Great for beginners
• CircuitPython Ready: Pre-loaded and configured
• Arduino Compatible: Familiar development environment
• More Capable: Significant upgrade from Arduino Uno
• Good Value: Excellent price/performance ratio

Limitations

• Superseded: Newer Metro M4 available with better specs
• 3.3V Logic: Requires level shifting for 5V devices
• Limited Performance: Slower than Metro M4
• Memory Constraints: Less memory than newer boards
• No FPU: No hardware floating point unit

Migration Path

For new projects, consider:

• Metro M4: More memory, faster processor, floating point
• Metro RP2040: Dual-core processor, more memory
• Feather M4: Smaller form factor with similar capabilities
• Circuit Playground Express: All-in-one learning board

Recommended Accessories

• Micro USB cable for programming
• 9V DC power adapter for standalone operation
• Level shifters for 5V device compatibility
• Sensors and actuators for projects
• Arduino shields (with level shifting if needed)