Adafruit METRO 328 without Headers
ATmega328-based Arduino-compatible board with GPIO, analog inputs, hardware UART, SPI, I2C, timers, and PWM. Includes USB-serial converter. Ships without headers.
ATmega328-based Arduino-compatible board with GPIO, analog inputs, hardware UART, SPI, I2C, timers, and PWM. Includes USB-serial converter. Ships without headers.
2 grouped connections are listed in the table but omitted from the graphic until individual pins are available.
External DC input for powering the METRO; Adafruit states 7-9V polarity-protected DC or 5V from micro USB.
5V board rail; product page states 5V logic and a 5V regulator with peak current limits.
3.3V regulator output; product page states a 3.3V regulator with peak current limits and optional 3.3V logic conversion by jumper.
Board ground rail for shields, headers, USB, and external circuits.
ATmega328P digital GPIO header group; Adafruit states the METRO has 20 GPIO pins and is Arduino UNO R3 shield/pin compatible.
PWM-capable digital outputs; Adafruit states 6 PWM outputs are available on 3 timers.
Six analogue input pins; Adafruit states 6 of the 20 GPIO are analogue inputs.
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.
Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.
Hardware I2C interface for Arduino-compatible shields and peripherals; product page lists hardware I2C.
Reset line for Arduino-compatible shields and programming/reset control.
Onboard red LED connected to PB5 according to the Adafruit product page.
| 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 |
2 grouped connections are omitted from the graphic until individual pins are available.
External DC input for powering the METRO; Adafruit states 7-9V polarity-protected DC or 5V from micro USB.
5V board rail; product page states 5V logic and a 5V regulator with peak current limits.
3.3V regulator output; product page states a 3.3V regulator with peak current limits and optional 3.3V logic conversion by jumper.
Board ground rail for shields, headers, USB, and external circuits.
ATmega328P digital GPIO header group; Adafruit states the METRO has 20 GPIO pins and is Arduino UNO R3 shield/pin compatible.
PWM-capable digital outputs; Adafruit states 6 PWM outputs are available on 3 timers.
Six analogue input pins; Adafruit states 6 of the 20 GPIO are analogue inputs.
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.
Hardware SPI interface exposed for shields/programming; product specifications list hardware SPI and a 6-pin ICSP header.
Hardware I2C interface for Arduino-compatible shields and peripherals; product page lists hardware I2C.
Reset line for Arduino-compatible shields and programming/reset control.
Onboard red LED connected to PB5 according to the Adafruit product page.
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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