Adafruit METRO 328 - Arduino Compatible - with Headers

ATmega328-based Arduino-compatible board, fully assembled with through-hole headers attached. Same as the Metro 328 without headers variant but with headers pre-soldered.

VIN / DC 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 I/O 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
UART / USB 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 · communicationVoltage · 5V logic by default; 3.3V if converted by jumper
SPI / 6-pin ICSP
Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.
Type · communicationVoltage · 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 · communicationVoltage · 5V logic by default; 3.3V if converted by jumper
RESET
Reset line for Arduino-compatible shields and programming/reset control.
Type · control
PB5 / onboard red LED
Onboard red LED connected to PB5 according to the Adafruit product page.
Type · indicatorVoltage · 5V logic by default

Pin	Type	Function	Voltage
VIN / DC 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 I/O 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
UART / USB serial	communication	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
SPI / 6-pin ICSP	communication	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	communication	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.
PB5 / onboard red LED	indicator	Onboard red LED connected to PB5 according to the Adafruit product page.	5V logic by default

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