Adafruit METRO M0 Express - designed for CircuitPython

Name: Adafruit METRO M0 Express - designed for CircuitPython
Brand: Adafruit
SKU: 3505

Adafruit METRO M0 Express - designed for CircuitPython — Adafruit — 3505

Arduino-form-factor board built around the ATSAMD21G18 ARM Cortex-M0+, designed for CircuitPython. Compatible with the Arduino IDE as a step up from the ATmega328-based Metro 328.

Logical pinout · physical placement not verified

2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.

Micro USB
Primary board power input over Micro USB; source states about 5 V at 500 mA, with temporary fuse shutoff above about 1000 mA.
Type · PowerVoltage · 5V USB input
DC jack
5.5 mm / 2.1 mm centre-positive DC input; source states provide about 6 V to 12 V to power the Metro.
Type · PowerVoltage · 6V-12V input
3V
Output from the 3.3 V regulator; source states it can supply 500 mA peak.
Type · PowerVoltage · 3.3V output
5V
5 V rail from the regulator when DC jack is used, or from USB; source states about 500 mA peak from USB and 800 mA peak from DC.
Type · PowerVoltage · 5V output
GND
Common ground for all power and logic.
Type · GroundVoltage · 0V
Vin
Higher of the DC jack or USB voltage; source gives 9 V example for DC input and 5 V when only USB is connected.
Type · PowerVoltage · USB/DC input rail
#0RX
GPIO 0 and Serial1 hardware UART receive input.
Type · UART, SignalVoltage · 3.3V logic
#1TX
GPIO 1 and Serial1 hardware UART transmit output.
Type · UART, SignalVoltage · 3.3V logic
#2-#12
General-purpose GPIO pins; source states most pins can do PWM output and all except D4 can be interrupt inputs.
Type · SignalVoltage · 3.3V logic
#13L
GPIO 13, connected to the red LED marked L next to the USB jack.
Type · SignalVoltage · 3.3V logic
SDA
I2C Wire data pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.
Type · I2CVoltage · 3.3V logic
SCL
I2C Wire clock pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.
Type · I2CVoltage · 3.3V logic
A0
Analogue input A0 and true analogue output via DAC; source states output can be set from 0 V to 3.3 V.
Type · AnalogVoltage · 0V-3.3V analogue
A1-A5
Analogue input pins that can also be used as digital I/O.
Type · AnalogVoltage · 3.3V logic / analogue input
SCK
Hardware SPI clock pin, also connected to the 2x3 SPI header.
Type · SPIVoltage · 3.3V logic
MOSI
Hardware SPI MOSI pin, also connected to the 2x3 SPI header.
Type · SPIVoltage · 3.3V logic
MISO
Hardware SPI MISO pin, also connected to the 2x3 SPI header.
Type · SPIVoltage · 3.3V logic
RST
Reset pin; tie to ground to manually reset the ATSAMD21 and launch the bootloader manually.
Type · ControlVoltage · 3.3V logic
ARef
External analogue reference input; source states it cannot go higher than 3.3 V.
Type · AnalogVoltage · <=3.3V reference
IORef
Digital reference voltage pin; source states it is the same as the 3.3 V logic voltage and cannot be changed.
Type · PowerVoltage · 3.3V reference
SWD header
2x5 0.05 inch SWD debug interface for trace debugging, external programming, or non-bootloader development.
Type · UnknownVoltage · 3.3V logic

Pin	Type	Function	Voltage
Micro USB	Power	Primary board power input over Micro USB; source states about 5 V at 500 mA, with temporary fuse shutoff above about 1000 mA.	5V USB input
DC jack	Power	5.5 mm / 2.1 mm centre-positive DC input; source states provide about 6 V to 12 V to power the Metro.	6V-12V input
3V	Power	Output from the 3.3 V regulator; source states it can supply 500 mA peak.	3.3V output
5V	Power	5 V rail from the regulator when DC jack is used, or from USB; source states about 500 mA peak from USB and 800 mA peak from DC.	5V output
GND	Ground	Common ground for all power and logic.	0V
Vin	Power	Higher of the DC jack or USB voltage; source gives 9 V example for DC input and 5 V when only USB is connected.	USB/DC input rail
#0RX	UART, Signal	GPIO 0 and Serial1 hardware UART receive input.	3.3V logic
#1TX	UART, Signal	GPIO 1 and Serial1 hardware UART transmit output.	3.3V logic
#2-#12	Signal	General-purpose GPIO pins; source states most pins can do PWM output and all except D4 can be interrupt inputs.	3.3V logic
#13L	Signal	GPIO 13, connected to the red LED marked L next to the USB jack.	3.3V logic
SDA	I2C	I2C Wire data pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.	3.3V logic
SCL	I2C	I2C Wire clock pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.	3.3V logic
A0	Analog	Analogue input A0 and true analogue output via DAC; source states output can be set from 0 V to 3.3 V.	0V-3.3V analogue
A1-A5	Analog	Analogue input pins that can also be used as digital I/O.	3.3V logic / analogue input
SCK	SPI	Hardware SPI clock pin, also connected to the 2x3 SPI header.	3.3V logic
MOSI	SPI	Hardware SPI MOSI pin, also connected to the 2x3 SPI header.	3.3V logic
MISO	SPI	Hardware SPI MISO pin, also connected to the 2x3 SPI header.	3.3V logic
RST	Control	Reset pin; tie to ground to manually reset the ATSAMD21 and launch the bootloader manually.	3.3V logic
ARef	Analog	External analogue reference input; source states it cannot go higher than 3.3 V.	<=3.3V reference
IORef	Power	Digital reference voltage pin; source states it is the same as the 3.3 V logic voltage and cannot be changed.	3.3V reference
SWD header	Unknown	2x5 0.05 inch SWD debug interface for trace debugging, external programming, or non-bootloader development.	3.3V logic

Logical pinout · physical placement not verified

2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.

Pin details

21 connections

Micro USB
Primary board power input over Micro USB; source states about 5 V at 500 mA, with temporary fuse shutoff above about 1000 mA.
PowerVoltage · 5V USB input
DC jack
5.5 mm / 2.1 mm centre-positive DC input; source states provide about 6 V to 12 V to power the Metro.
PowerVoltage · 6V-12V input
3V
Output from the 3.3 V regulator; source states it can supply 500 mA peak.
PowerVoltage · 3.3V output
5V
5 V rail from the regulator when DC jack is used, or from USB; source states about 500 mA peak from USB and 800 mA peak from DC.
PowerVoltage · 5V output
GND
Common ground for all power and logic.
GroundVoltage · 0V
Vin
Higher of the DC jack or USB voltage; source gives 9 V example for DC input and 5 V when only USB is connected.
PowerVoltage · USB/DC input rail
#0RX
GPIO 0 and Serial1 hardware UART receive input.
UART, SignalVoltage · 3.3V logic
#1TX
GPIO 1 and Serial1 hardware UART transmit output.
UART, SignalVoltage · 3.3V logic
#2-#12
General-purpose GPIO pins; source states most pins can do PWM output and all except D4 can be interrupt inputs.
SignalVoltage · 3.3V logic
#13L
GPIO 13, connected to the red LED marked L next to the USB jack.
SignalVoltage · 3.3V logic
SDA
I2C Wire data pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.
I2CVoltage · 3.3V logic
SCL
I2C Wire clock pin; source notes no default pull-up, so an external 2.2 kΩ to 10 kΩ pull-up may be needed.
I2CVoltage · 3.3V logic
A0
Analogue input A0 and true analogue output via DAC; source states output can be set from 0 V to 3.3 V.
AnalogVoltage · 0V-3.3V analogue
A1-A5
Analogue input pins that can also be used as digital I/O.
AnalogVoltage · 3.3V logic / analogue input
SCK
Hardware SPI clock pin, also connected to the 2x3 SPI header.
SPIVoltage · 3.3V logic
MOSI
Hardware SPI MOSI pin, also connected to the 2x3 SPI header.
SPIVoltage · 3.3V logic
MISO
Hardware SPI MISO pin, also connected to the 2x3 SPI header.
SPIVoltage · 3.3V logic
RST
Reset pin; tie to ground to manually reset the ATSAMD21 and launch the bootloader manually.
ControlVoltage · 3.3V logic
ARef
External analogue reference input; source states it cannot go higher than 3.3 V.
AnalogVoltage · <=3.3V reference
IORef
Digital reference voltage pin; source states it is the same as the 3.3 V logic voltage and cannot be changed.
PowerVoltage · 3.3V reference
SWD header
2x5 0.05 inch SWD debug interface for trace debugging, external programming, or non-bootloader development.
UnknownVoltage · 3.3V logic

Start wiring

USB · 3.3 V

Confirm the data interface matches your host board.

Module pins: Micro USB, DC jack, 3V, 5V, Vin, IORef, GND, #0 / RX. Schematik maps them to your board in the app.

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