Name: Adafruit METRO 328 without Headers
Brand: Adafruit
SKU: 2466

Logical pinout · physical placement not verified

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

VINDC jack input
External DC input for powering the METRO; Adafruit states 7-9V polarity-protected DC or 5V from micro USB.
Type · PowerVoltage · 7-9V DC on external input, or 5V from micro USB per Adafruit product page
5V
5V board rail; product page states 5V logic and a 5V regulator with peak current limits.
Type · PowerVoltage · 5V
3.3V
3.3V regulator output; product page states a 3.3V regulator with peak current limits and optional 3.3V logic conversion by jumper.
Type · PowerVoltage · 3.3V
GND
Board ground rail for shields, headers, USB, and external circuits.
Type · GroundVoltage · 0V
Digital IO D0-D13
ATmega328P digital GPIO header group; Adafruit states the METRO has 20 GPIO pins and is Arduino UNO R3 shield/pin compatible.
Type · GPIOVoltage · 5V logic by default; can be converted to 3.3V logic by jumper per Adafruit
PWM outputs
PWM-capable digital outputs; Adafruit states 6 PWM outputs are available on 3 timers.
Type · GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
Analog inputs A0-A5
Six analogue input pins; Adafruit states 6 of the 20 GPIO are analogue inputs.
Type · AnalogVoltage · 5V logic/reference domain by default; 3.3V if converted by jumper
UARTUSB serial
Hardware UART connected through the onboard USB-to-serial converter for programming and serial communication; Adafruit notes two GPIO are reserved for the USB-serial converter and RX/TX LEDs.
Type · GPIO, UARTVoltage · 5V logic by default; 3.3V if converted by jumper
SPI6-pin ICSP
Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.
Type · GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
I2C
Hardware I2C interface for Arduino-compatible shields and peripherals; product page lists hardware I2C.
Type · GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
RESET
Reset line for Arduino-compatible shields and programming/reset control.
Type · Control
PB5onboard red LED
Onboard red LED connected to PB5 according to the Adafruit product page.
Type · UnknownVoltage · 5V logic by default

Pin	Type	Function	Voltage
VINDC jack input	Power	External DC input for powering the METRO; Adafruit states 7-9V polarity-protected DC or 5V from micro USB.	7-9V DC on external input, or 5V from micro USB per Adafruit product page
5V	Power	5V board rail; product page states 5V logic and a 5V regulator with peak current limits.	5V
3.3V	Power	3.3V regulator output; product page states a 3.3V regulator with peak current limits and optional 3.3V logic conversion by jumper.	3.3V
GND	Ground	Board ground rail for shields, headers, USB, and external circuits.	0V
Digital IO D0-D13	GPIO	ATmega328P digital GPIO header group; Adafruit states the METRO has 20 GPIO pins and is Arduino UNO R3 shield/pin compatible.	5V logic by default; can be converted to 3.3V logic by jumper per Adafruit
PWM outputs	GPIO	PWM-capable digital outputs; Adafruit states 6 PWM outputs are available on 3 timers.	5V logic by default; 3.3V if converted by jumper
Analog inputs A0-A5	Analog	Six analogue input pins; Adafruit states 6 of the 20 GPIO are analogue inputs.	5V logic/reference domain by default; 3.3V if converted by jumper
UARTUSB serial	GPIO, UART	Hardware UART connected through the onboard USB-to-serial converter for programming and serial communication; Adafruit notes two GPIO are reserved for the USB-serial converter and RX/TX LEDs.	5V logic by default; 3.3V if converted by jumper
SPI6-pin ICSP	GPIO	Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.	5V logic by default; 3.3V if converted by jumper
I2C	GPIO	Hardware I2C interface for Arduino-compatible shields and peripherals; product page lists hardware I2C.	5V logic by default; 3.3V if converted by jumper
RESET	Control	Reset line for Arduino-compatible shields and programming/reset control.
PB5onboard red LED	Unknown	Onboard red LED connected to PB5 according to the Adafruit product page.	5V logic by default

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

12 connections

VINDC jack input
External DC input for powering the METRO; Adafruit states 7-9V polarity-protected DC or 5V from micro USB.
PowerVoltage · 7-9V DC on external input, or 5V from micro USB per Adafruit product page
5V
5V board rail; product page states 5V logic and a 5V regulator with peak current limits.
PowerVoltage · 5V
3.3V
3.3V regulator output; product page states a 3.3V regulator with peak current limits and optional 3.3V logic conversion by jumper.
PowerVoltage · 3.3V
GND
Board ground rail for shields, headers, USB, and external circuits.
GroundVoltage · 0V
Digital IO D0-D13
ATmega328P digital GPIO header group; Adafruit states the METRO has 20 GPIO pins and is Arduino UNO R3 shield/pin compatible.
GPIOVoltage · 5V logic by default; can be converted to 3.3V logic by jumper per Adafruit
PWM outputs
PWM-capable digital outputs; Adafruit states 6 PWM outputs are available on 3 timers.
GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
Analog inputs A0-A5
Six analogue input pins; Adafruit states 6 of the 20 GPIO are analogue inputs.
AnalogVoltage · 5V logic/reference domain by default; 3.3V if converted by jumper
UARTUSB serial
Hardware UART connected through the onboard USB-to-serial converter for programming and serial communication; Adafruit notes two GPIO are reserved for the USB-serial converter and RX/TX LEDs.
GPIO, UARTVoltage · 5V logic by default; 3.3V if converted by jumper
SPI6-pin ICSP
Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.
GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
I2C
Hardware I2C interface for Arduino-compatible shields and peripherals; product page lists hardware I2C.
GPIOVoltage · 5V logic by default; 3.3V if converted by jumper
RESET
Reset line for Arduino-compatible shields and programming/reset control.
Control
PB5onboard red LED
Onboard red LED connected to PB5 according to the Adafruit product page.
UnknownVoltage · 5V logic by default

Start wiring

USB · 3.3 V

Confirm the data interface matches your host board.

Module pins: VIN / DC jack input, 5V, 3.3V, GND, Digital I/O D0-D13, PWM outputs, Analog inputs A0-A5. Schematik maps them to your board in the app.

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