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Microcontroller
Adafruit ItsyBitsy M4 Express
A small, fast SAMD51 stick board with QSPI flash for CircuitPython, a common step up from M0 boards when projects need more speed and RAM.
Processor
Microchip ATSAMD51G19 Arm Cortex-M4F @ 120 MHz
Logic
3.3 V GPIO
Power
Micro-USB or BAT/VHI input
Format
36 x 18 mm stick
Check before wiring
- Inputs are 3.3 V only; only the dedicated level-shifted output pin is 5 V.
- No battery charger onboard despite the BAT pin.
- Double-press reset enters the UF2 bootloader; single-press just resets.
Interfaces
GPIOI2CSPIUARTADCDACPWMUSB
Source-backed connector
Interactive pin map
Pin map
Connector
ItsyBitsy M4 Express castellated edges
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.
- ATSAMD51G19 at 120 MHz; pinout from the official Adafruit learn guide.
- GPIO is 3.3 V only; VHI is a level-shifted output that tracks VHI (VBAT or USB 5 V).
- A0 doubles as DAC0; A1 doubles as DAC1.
- Double-tap reset enters the UF2 bootloader; single reset just restarts.
All 31 pins (table)
| # | Signal | Role | Net | Also / notes |
|---|---|---|---|---|
| Bottom edge | ||||
| 1 | System | |||
| 2 | Power | 3V3 | ||
| 3 | Power | 3V3 | ||
| 4 | Power | VHI | Level-shifted 5 V output (tracks VBAT/USB). | |
| 5 | DAC | DAC0 / PA02 | ||
| 6 | DAC | DAC1 / PA05 | ||
| 7 | ADC | PB08 | ||
| 8 | ADC | PB09 | ||
| 9 | GPIO | PA17 | ||
| 10 | GPIO | PA16 | ||
| 11 | SPI | SPI | PA13 | |
| 12 | SPI | SPI | PA12 | |
| 13 | SPI | SPI | PA14 | |
| Top edge | ||||
| 14 | Power | BAT | Battery voltage input. | |
| 15 | System | 3.3 V regulator enable (active HIGH). | ||
| 16 | Power | USB | USB 5 V bus. | |
| 17 | GPIO | PA11 | ||
| 18 | GPIO | PA10 | ||
| 19 | GPIO | PA16 | ||
| 20 | GPIO | PA18 | ||
| 21 | GPIO | PA19 | ||
| 22 | GPIO | PA20 | ||
| 23 | Alt | PA15 · Output only; level-shifted to VHI. | ||
| 24 | I2C | I2C | PA22 | |
| 25 | I2C | I2C | PA23 | |
| 26 | UART | UART | PA09 | |
| 27 | UART | UART | PA08 | |
| Short edge | ||||
| 28 | System | |||
| 29 | GPIO | |||
| 30 | GPIO | |||
| 31 | GPIO | |||
Why it matters
- Learn-guide pinout page documents every pad and alternate function.
- 2 MB QSPI flash for CircuitPython filesystems.
- Special 5 V-level output pin for driving NeoPixels from 3.3 V logic boards.
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