Loading source-backed pinouts…
Microcontroller
Adafruit Grand Central M4 Express
A high-pin-count SAMD51 board in the Arduino Mega footprint, aimed at projects needing many headers plus CircuitPython support.
Processor
Microchip ATSAMD51P20 Arm Cortex-M4F
Logic
3.3 V GPIO
Power
USB, barrel jack, VIN
Format
Mega shield layout
Check before wiring
- The Mega-like footprint does not mean 5 V IO tolerance.
- Check which pins are shared with SD card and onboard peripherals.
- High pin count makes alternate-function conflicts easy to miss.
Interfaces
GPIOI2CSPIUARTADCDACPWMUSB
Source-backed connector
Interactive pin map
Pin map
Connector
Mega-compatible shield headers
Signals grouped by function — schematic layout, not to physical scale
Dense header — open Full view for a roomier, fully-labelled diagram.
Simplified diagram, grouped by function — not to physical scale. Pin data is source-backed; verify against the linked documentation.
Hover, tap, or focus a pad to inspect a pin. Use arrow keys to move between pins.
- All GPIO uses 3.3 V logic and is not 5 V tolerant.
- QSPI flash, microSD, NeoPixel, and status LED signals are board resources and should not be reassigned casually.
- D50-D53 form the dedicated SPI header-compatible signal group; alternate SERCOM assignments are pin-mux dependent.
All 78 pins (table)
| # | Signal | Role | Net | Also / notes |
|---|---|---|---|---|
| Digital D0-D53 | ||||
| 1 | UART | UART | ||
| 2 | UART | UART | ||
| 3 | GPIO | |||
| 4 | GPIO | |||
| 5 | GPIO | |||
| 6 | GPIO | |||
| 7 | GPIO | |||
| 8 | GPIO | |||
| 9 | GPIO | |||
| 10 | GPIO | |||
| 11 | GPIO | |||
| 12 | GPIO | |||
| 13 | GPIO | |||
| 14 | GPIO | |||
| 15 | UART | UART | ||
| 16 | UART | UART | ||
| 17 | UART | UART | ||
| 18 | UART | UART | ||
| 19 | UART | UART | ||
| 20 | UART | UART | ||
| 21 | I2C | I2C | ||
| 22 | I2C | I2C | ||
| 23 | GPIO | |||
| 24 | GPIO | |||
| 25 | GPIO | |||
| 26 | GPIO | |||
| 27 | GPIO | |||
| 28 | GPIO | |||
| 29 | GPIO | |||
| 30 | GPIO | |||
| 31 | GPIO | |||
| 32 | GPIO | |||
| 33 | GPIO | |||
| 34 | GPIO | |||
| 35 | GPIO | |||
| 36 | GPIO | |||
| 37 | GPIO | |||
| 38 | GPIO | |||
| 39 | GPIO | |||
| 40 | GPIO | |||
| 41 | GPIO | |||
| 42 | GPIO | |||
| 43 | GPIO | |||
| 44 | GPIO | |||
| 45 | GPIO | |||
| 46 | GPIO | |||
| 47 | GPIO | |||
| 48 | GPIO | |||
| 49 | GPIO | |||
| 50 | GPIO | |||
| 51 | SPI | SPI | ||
| 52 | SPI | SPI | ||
| 53 | SPI | SPI | ||
| 54 | SPI | SPI | ||
| Analog A0-A15 | ||||
| 1 | ADC | |||
| 2 | ADC | |||
| 3 | ADC | |||
| 4 | ADC | |||
| 5 | ADC | |||
| 6 | ADC | |||
| 7 | ADC | |||
| 8 | ADC | |||
| 9 | ADC | |||
| 10 | ADC | |||
| 11 | ADC | |||
| 12 | ADC | |||
| 13 | ADC | |||
| 14 | ADC | |||
| 15 | ADC | |||
| 16 | ADC | |||
| Power and control | ||||
| 1 | Power | 3V3 | ||
| 2 | Power | 5V | ||
| 3 | Ground | GND | ||
| 4 | Power | VIN | ||
| 5 | System | |||
| 6 | ADC | |||
| 7 | I2C | I2C | ||
| 8 | I2C | I2C | ||
Why it matters
- Official pinout documents the many Mega-style header positions.
- Large SAMD51 package exposes many more pins than Feather boards.
- QSPI flash and microSD support are useful for data-heavy projects.
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