Adafruit Metro M4 Express AirLift (WiFi) - Lite
Metro M4 development board with Microchip ATSAMD51 at 120 MHz and an on-board ESP32 WiFi co-processor with pre-loaded TLS root certificates.
Pinout
2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.
- USB
Micro USB power/data connection; Adafruit states it is one primary way to power the Metro M4 Express AirLift.
Type · USBVoltage · USB 5V input, fused; guide states up to about 500mA across Vin/5V/3.3V supplies combined - DC jack
5.5mm/2.1mm centre-positive DC input jack; Adafruit states it is the other primary power input.
Type · PowerVoltage · 6V-12V input stated by Adafruit guide - VIN
Board VIN supply rail available on the Metro header, tied to external input power path per pinouts guide power section.
Type · Power - 5V
5V board supply rail exposed on the Metro header.
Type · PowerVoltage · 5V - 3.3V
Regulated 3.3V board supply rail exposed on the Metro header.
Type · PowerVoltage · 3.3V - GND
Ground pins on the Metro headers.
Type · Ground - #0RX
GPIO #0, receive input for Serial1 hardware UART, per Adafruit pinouts guide.
Type · UART, SignalVoltage · 3.3V logic - #1TX
GPIO #1, transmit output for Serial1 hardware UART, per Adafruit pinouts guide.
Type · UART, SignalVoltage · 3.3V logic - #2-#12
General-purpose digital GPIO pins; guide states all logic pins are 3.3V and interrupt-capable.
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 on the Metro header.
Type · I2CVoltage · 3.3V logic - SCL
I2C/Wire clock pin on the Metro header; guide notes SCL is the exception to PWM availability.
Type · I2CVoltage · 3.3V logic - A0-A5
Analogue-capable header pins; A0 has true analogue output per Adafruit pinouts guide.
Type · SignalVoltage · 3.3V logic/analogue domain - SPI
SPI bus exposed for board peripherals and header use; ESP32 AirLift uses SPI data plus dedicated control pins.
Type · SignalVoltage · 3.3V logic - ESP_CSSPIWIFI_SS36
ESP32 AirLift chip-select pin for WiFi SPI interface, named by Adafruit guide.
Type · SignalVoltage · 3.3V logic - ESP_BUSYSPIWIFI_ACK37
ESP32 AirLift ready/busy acknowledgement pin, named by Adafruit guide.
Type · SignalVoltage · 3.3V logic - ESP_RESETSPIWIFI_RESET38
ESP32 AirLift reset pin, named by Adafruit guide.
Type · SignalVoltage · 3.3V logic - ESP_RXESP_TX
Dedicated UART between the main MCU and ESP32 AirLift; guide states it is separate from the Metro RX/TX breakout pins.
Type · SignalVoltage · 3.3V logic - ESP_RTS34
ESP32 RTS pin exposed for advanced serial contexts, per Adafruit guide.
Type · SignalVoltage · 3.3V logic - ESP_GPIO035
ESP32 GPIO0 bootloader-enable pin, per Adafruit guide.
Type · SignalVoltage · 3.3V logic
| Pin | Type | Function | Voltage |
|---|---|---|---|
| USB | USB | Micro USB power/data connection; Adafruit states it is one primary way to power the Metro M4 Express AirLift. | USB 5V input, fused; guide states up to about 500mA across Vin/5V/3.3V supplies combined |
| DC jack | Power | 5.5mm/2.1mm centre-positive DC input jack; Adafruit states it is the other primary power input. | 6V-12V input stated by Adafruit guide |
| VIN | Power | Board VIN supply rail available on the Metro header, tied to external input power path per pinouts guide power section. | |
| 5V | Power | 5V board supply rail exposed on the Metro header. | 5V |
| 3.3V | Power | Regulated 3.3V board supply rail exposed on the Metro header. | 3.3V |
| GND | Ground | Ground pins on the Metro headers. | |
| #0RX | UART, Signal | GPIO #0, receive input for Serial1 hardware UART, per Adafruit pinouts guide. | 3.3V logic |
| #1TX | UART, Signal | GPIO #1, transmit output for Serial1 hardware UART, per Adafruit pinouts guide. | 3.3V logic |
| #2-#12 | Signal | General-purpose digital GPIO pins; guide states all logic pins are 3.3V and interrupt-capable. | 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 on the Metro header. | 3.3V logic |
| SCL | I2C | I2C/Wire clock pin on the Metro header; guide notes SCL is the exception to PWM availability. | 3.3V logic |
| A0-A5 | Signal | Analogue-capable header pins; A0 has true analogue output per Adafruit pinouts guide. | 3.3V logic/analogue domain |
| SPI | Signal | SPI bus exposed for board peripherals and header use; ESP32 AirLift uses SPI data plus dedicated control pins. | 3.3V logic |
| ESP_CSSPIWIFI_SS36 | Signal | ESP32 AirLift chip-select pin for WiFi SPI interface, named by Adafruit guide. | 3.3V logic |
| ESP_BUSYSPIWIFI_ACK37 | Signal | ESP32 AirLift ready/busy acknowledgement pin, named by Adafruit guide. | 3.3V logic |
| ESP_RESETSPIWIFI_RESET38 | Signal | ESP32 AirLift reset pin, named by Adafruit guide. | 3.3V logic |
| ESP_RXESP_TX | Signal | Dedicated UART between the main MCU and ESP32 AirLift; guide states it is separate from the Metro RX/TX breakout pins. | 3.3V logic |
| ESP_RTS34 | Signal | ESP32 RTS pin exposed for advanced serial contexts, per Adafruit guide. | 3.3V logic |
| ESP_GPIO035 | Signal | ESP32 GPIO0 bootloader-enable pin, per Adafruit guide. | 3.3V logic |
2 grouped source records are expanded into separate logical pads where unambiguous; physical placement is not implied.
Pin details
20 connections- USB
Micro USB power/data connection; Adafruit states it is one primary way to power the Metro M4 Express AirLift.
USBVoltage · USB 5V input, fused; guide states up to about 500mA across Vin/5V/3.3V supplies combined - DC jack
5.5mm/2.1mm centre-positive DC input jack; Adafruit states it is the other primary power input.
PowerVoltage · 6V-12V input stated by Adafruit guide - VIN
Board VIN supply rail available on the Metro header, tied to external input power path per pinouts guide power section.
Power - 5V
5V board supply rail exposed on the Metro header.
PowerVoltage · 5V - 3.3V
Regulated 3.3V board supply rail exposed on the Metro header.
PowerVoltage · 3.3V - GND
Ground pins on the Metro headers.
Ground - #0RX
GPIO #0, receive input for Serial1 hardware UART, per Adafruit pinouts guide.
UART, SignalVoltage · 3.3V logic - #1TX
GPIO #1, transmit output for Serial1 hardware UART, per Adafruit pinouts guide.
UART, SignalVoltage · 3.3V logic - #2-#12
General-purpose digital GPIO pins; guide states all logic pins are 3.3V and interrupt-capable.
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 on the Metro header.
I2CVoltage · 3.3V logic - SCL
I2C/Wire clock pin on the Metro header; guide notes SCL is the exception to PWM availability.
I2CVoltage · 3.3V logic - A0-A5
Analogue-capable header pins; A0 has true analogue output per Adafruit pinouts guide.
SignalVoltage · 3.3V logic/analogue domain - SPI
SPI bus exposed for board peripherals and header use; ESP32 AirLift uses SPI data plus dedicated control pins.
SignalVoltage · 3.3V logic - ESP_CSSPIWIFI_SS36
ESP32 AirLift chip-select pin for WiFi SPI interface, named by Adafruit guide.
SignalVoltage · 3.3V logic - ESP_BUSYSPIWIFI_ACK37
ESP32 AirLift ready/busy acknowledgement pin, named by Adafruit guide.
SignalVoltage · 3.3V logic - ESP_RESETSPIWIFI_RESET38
ESP32 AirLift reset pin, named by Adafruit guide.
SignalVoltage · 3.3V logic - ESP_RXESP_TX
Dedicated UART between the main MCU and ESP32 AirLift; guide states it is separate from the Metro RX/TX breakout pins.
SignalVoltage · 3.3V logic - ESP_RTS34
ESP32 RTS pin exposed for advanced serial contexts, per Adafruit guide.
SignalVoltage · 3.3V logic - ESP_GPIO035
ESP32 GPIO0 bootloader-enable pin, per Adafruit guide.
SignalVoltage · 3.3V logic
Start wiring
USB · 3.3 V
Confirm the data interface matches your host board.
Module pins: USB, DC jack, VIN, 5V, 3.3V, GND, #0 / RX, #1 / TX. Schematik maps them to your board in the app.
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