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The Adafruit Grand Central M4 Express is a powerful development board built around the Microchip ATSAMD51P20 — a 120 MHz Cortex M4 processor with hardware fl...

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The Adafruit Grand Central M4 Express is a powerful development board built around the Microchip ATSAMD51P20 — a 120 MHz Cortex M4 processor with hardware floating point, 1 MB Flash, and 256 KB RAM. In the familiar Arduino Mega form factor, it brings 70 GPIO pins, dual DACs, 15 analog inputs, 8 MB QSPI Flash, an SD card slot, and a NeoPixel to your projects.

This version comes with headers pre-soldered, ready to plug into breadboards and accept shield connections. The front half shares the same pinout as Adafruit Metro boards, making it compatible with Arduino shields. It supports both CircuitPython and Arduino IDE, with a UF2 bootloader for drag-and-drop firmware loading over USB.

Key Features

  • ATSAMD51P20 Cortex M4 at 120 MHz – Hardware DSP and floating point support
  • 1 MB Flash, 256 KB RAM – 32-bit, 3.3V logic and power
  • 70 GPIO Pins Total – 62 accessible GPIO, 16 analog inputs, 2 true analog outputs (DAC)
  • 8 Hardware SERCOM – Configurable as I²C, SPI, or UART
  • 22 PWM Outputs – For servos, LEDs, and motor control
  • Stereo I²S Input/Output – With MCK pin for audio projects
  • 12-bit Parallel Capture Controller – For camera and video input
  • Built-in Crypto Engines – AES-256, true RNG, and public key controller
  • 8 MB QSPI Flash – Acts as storage for CircuitPython scripts and files, or as a datalogger in Arduino
  • Micro SD Card Slot – Removable storage via SPI
  • Native USB – Serial, HID keyboard/mouse, and UF2 bootloader for drag-and-drop programming
  • Flexible Power – 7–9V DC via 2.1 mm jack (with on/off switch) or 5V via Micro-USB, with automatic switching
  • Status LEDs and NeoPixel – Green power LED, RX/TX LEDs, red indicator LED, and one RGB NeoPixel

Ideal For

  • Complex projects needing many I/O pins (Arduino Mega replacement)
  • CircuitPython development with high performance and large storage
  • Audio, sensor logging, and data-heavy applications
  • Prototyping with breadboards and Arduino shields

Package Contents

  • 1× Adafruit Grand Central M4 Express (with headers) – Assembled, tested, and ready to use
Tip: Need a lower-profile option? The Grand Central M4 (Without Headers) ships without through-hole components soldered, ideal for custom builds and tight spaces.

Resources

Jargon buster

Plain-language definitions for the technical terms used above.

Bootloader
Small starter software on a microcontroller that lets new code be uploaded before the main program runs. Knowing how to enter bootloader mode matters when you need to program the board or recover it after a faulty sketch.
CircuitPython
A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.
DAC
A digital-to-analogue converter turns numbers from the microcontroller into a real analogue voltage. It matters if you want to generate simple waveforms, audio-style signals, or variable control voltages rather than just on/off outputs.
GPIO
General-purpose input/output pins are microcontroller pins you can set in software to read signals, switch devices on and off, or connect to peripherals. The number of GPIO pins matters because it limits how many buttons, LEDs, sensors, and other parts you can wire directly to the board.
Headers
Rows of metal pins used to plug a module into a breadboard or connect it with jumper wires. Pre-soldered headers make the module easier to use straight away without needing to solder the pins yourself.
HID
Human Interface Device is a USB device class used for keyboards, mice, gamepads and similar controls. If a board supports HID over USB, it can act like an input device to a computer without needing a custom driver.
IDE
Short for Integrated Development Environment, a program used to write, run and manage code. It matters because some learners prefer a traditional coding workspace instead of a guided notebook-style lesson.
LED
A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
native USB
Native USB means the microcontroller itself handles USB communication, rather than using a separate USB-to-serial chip. This matters for programming, debugging, and projects that need the board to act directly as a USB device.
NeoPixel
A type of addressable LED system where colour data is sent along a single digital data line from one LED or controller to the next. Compatibility matters because the timing and signal format must match for the lights or driver board to respond correctly.
PWM
Pulse Width Modulation is a way for a digital pin to simulate variable output power by switching on and off very quickly. It matters for controlling things like LED brightness, motor speed, or servo-style signals from a microcontroller pin.
RAM
RAM is temporary memory used while a device is running, and its contents are lost when power is removed. A “Run in RAM” mode is useful for testing settings without permanently programming the module, but it may not support every feature.
RGB
Short for red, green and blue, usually referring to an LED that can mix those three colours. It matters because controlling an RGB LED teaches how separate outputs combine to create different colours.
Shield
An add-on board that plugs into a main controller board to give it extra features such as sensing, motor control or communication. Knowing a product supports shields helps you judge whether it can connect neatly into an existing maker-board setup.
SPI
A fast serial communication bus often used for displays, memory cards, and sensors. It matters because SPI devices need specific pins for clock and data, plus a separate chip-select line for each device.
UART
UART is a simple serial connection that sends data over separate transmit and receive wires, often labelled TX and RX. It matters because this module is designed to replace a wired UART cable with a wireless link while keeping the same serial data format.
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