This Feather has a lot going on! This page details all of the pin-specific information and various capabilities.

PrettyPins PDF on GitHub.

Power Pins, Connections, and Charge LED

• USB C connector - This is used for power and data. Connect to your computer via a USB C cable to update firmware and edit code.
• LiPoly Battery connector - This 2-pin JST PH connector allows you to plug in LiPoly batteries to power the Feather. The Feather is also capable of charging batteries plugged into this port via USB.
• chg LED - This small LED is located below the USB C connector. This indicates the charge status of a connected LiPoly battery when charging over USB. Note, it's normal for this LED to flicker when no battery is in place, that's the charge circuitry trying to detect whether a battery is there or not.
• GND - This is the common ground for all power and logic.
• BAT - This is the positive voltage to/from the 2-pin JST PH jack for the optional LiPoly battery.
• USB - This is the positive voltage to/from the USB C connector, if USB is connected.
• EN - This is the 3.3V regulator's enable pin. It's pulled up, so connect to ground to disable the 3.3V regulator.
• 3.3V - These pins are the output from the 3.3V regulator, they can supply 500mA peak.

• LiPo Chg - On the back of the board, behind the USB-C port, is the LiPo charge jumper. If you cut this jumper, it disconnects the lipoly battery charging circuit from the JST PH connector. As a result, you can safely use AA and AAA battery packs after cutting the jumper.

Logic Pins

I2C and SPI on RP2040

The RP2040 is capable of handling I2C, SPI and UART on many pins. However, there are really only two peripherals each of I2C, SPI and UART: I2C0 and I2C1, SPI0 and SPI1, and UART0 and UART1. So while many pins are capable of I2C, SPI and UART, you can only do two at a time, and only on separate peripherals, 0 and 1. I2C, SPI and UART peripherals are included and numbered below.

PWM on RP2040

The RP2040 supports PWM on all pins. However, it is not capable of PWM on all pins at the same time. There are 8 PWM "slices", each with two outputs, A and B. Each pin on the Feather is assigned a PWM slice and output. For example, A0 is PWM5 A, which means it is first output of the fifth slice. You can have up to 15 PWM objects on this Feather. The important thing to know is that you cannot use the same slice and output more than once at the same time. So, if you have a PWM object on pin A0, you cannot also put a PWM object on D10, because they are both PWM5 A. The PWM slices and outputs are indicated below. Note that PWM3 B is not available on this Feather because the pin is not broken out.

Analog Pins

The RP2040 has four ADCs. These pins are the only pins capable of handling analog, and they can also do digital.

• A0/GPIO26 - This pin is ADC0. It is also SPI1 SCK, I2C1 SDA and PWM5 A.
• A1/GPIO27 - This pin is ADC1. It is also SPI1 MOSI, I2C1 SCL and PWM5 B.
• A2/GPIO28 - This pin is ADC2. It is also SPI1 MISO, I2C1 SDA and PWM6 A.
• A3/GPIO29 - This pin is ADC3. It is also SPI1 CS, I2C0 SCL and PWM6 B.

Digital Pins

These are the digital I/O pins. They all have multiple capabilities.

• D24/GPIO24 - Digital I/O pin 24. It is also UART1 TX, I2C0 SDA, and PWM4 A.
• D25/GPIO25 - Digital I/O pin 25. It is also UART1 RX, I2C0 SCL, and PWM4 B.
• SCK/GPIO14 - The main SPI1 SCK. It is also I2C1 SDA, and PWM7 A.
• MO/GPIO15 - The main SPI1 MOSI. It is also I2C1 SCL, and PWM7 B.
• MI/GPIO8 - The main SPI1 MISO. It is also UART1 TX, I2C0 SDA, and PWM4 A.
• RX/GPIO1 - The main UART0 RX pin. It is also I2C0 SDA, SPI0 CS and PWM0 B.
• TX/GPIO0 - The main UART0 TX pin. It is also I2C0 SCL, SPI0 MISO and PWM0 A.
• D4/GPIO4 - Digital I/O pin 4. It is also RX0, TX1, SDA0 and PWM2A.
• D13/GPIO13 - Digital I/O pin 13. It is also SPI1 CS, UART0 RX, I2C0 SCL and PWM6 B.
• D12/GPIO12 - Digital I/O pin 12. It is also SPI1 MISO, UART0 TX, I2C0 SDA and PWM6 A.
• D11/GPIO11 - Digital I/O pin 11. It is also SPI1 MOSI, I2C1 SCL and PWM5 B.
• D10/GPIO10 - Digital I/O pin 10. It is also SPI1 SCK, I2C1 SDA and PWM5 A.
• D9/GPIO9 - Digital I/O pin 9. It is also SPI1 CS, UART1 RX, I2C0 SCL and PWM4 B.
• D6/GPIO6 - Digital I/O pin 6. It is also SPI0 SCK, I2C1 SDA, and PWM3 A.
• D5/GPIO5 - Digital I/O pin 5. It is also SPI0 CS, UART1 RX, I2C0 SCL, and PWM2 B.
• D4/GPIO4 - Digital I/O pin 4. It is also RX0, TX1, SDA0 and PWM2 A.
• SCL/GPIO3 - The main I2C1 clock pin. It is also SPI0 MOSI, I2C1 SCL and PWM1 B.
• SDA/GPIO2 - The main I2C1 data pin. It is also SPI0 SCK, I2C1 SDA and PWM1 A.

CircuitPython I2C, SPI and UART

Note that in CircuitPython, there is a board object each for STEMMA QT, I2C, SPI and UART that use the connector and pins labeled on the Feather. You can use these objects to initialize these peripherals in your code.

• board.STEMMA_I2C() uses the STEMMA QT connector (in this case, SCL/SDA pins)
• board.I2C() uses SCL/SDA pins (GPIO2 and GPIO3)
• board.SPI() uses SCK/MO/MI pins (GPIO14, GPIO15 and GPIO8)
• board.UART() uses RX/TX pins (GPIO0 and GPIO1)

Arduino I2C, SPI and UART

I2C, SPI and UART can be accessed with these objects in Arduino:

• Wire is used for the default I2C and STEMMA QT connector (GPIO2 and GPIO3).
• SPI is used for the default SPI pins (GPIO14, GPIO15 and GPIO8).
• Serial1 is used for the default UART pins (GPIO0 and GPIO1).

The peripheral order is defined in the board support definition for Arduino. For example, you'll notice that even though the default I2C (GPIO2 and GPIO3) is located on I2C1, it is defined as Wire rather than Wire1.

GPIO Pins by Pin Functionality

Primary pins based on the silkscreen pin labels are bold.

I2C Pins

• I2C0 SCL: A3, D25, RX, D13, D9, D5
• I2C0 SDA: A2, D24, MISO, TX, D12, D4
• I2C1 SCL: SCL, A1, MOSI, D11
• I2C1 SDA: SDA, A0, SCK, D10, D6

SPI Pins

• SPI0 SCK: D6, SDA
• SPI0 MOSI: SCL
• SPI0 MISO: TX
• SPI0 CS: RX, D5
• SPI1 SCK: SCK, A0, D10
• SPI1 MOSI: MOSI, A1, D11
• SPI1 MISO: MISO, A2, D24, D12
• SPI1 CS: A3, D25, D13, D9

UART Pins

• UART0 TX: TX, A2, D12
• UART0 RX: RX, A3, D13, D4
• UART1 TX: D24, MISO, D4
• UART1 RX: D25, D9, D5

PWM Pins

• PWM0 A: TX
• PWM0 B: RX
• PWM1 A: SDA
• PWM1 B: SCL
• PWM2 A: D4
• PWM2 B: D5
• PWM3 A: D6
• PWM3 B: (none)
• PWM4 A: D24, MISO
• PWM4 B: D25, D9
• PWM5 A: A0, D10
• PWM5 B: A1, D11
• PWM6 A: A2, D12
• PWM6 B: A3, D13
• PWM7 A: SCK
• PWM7 B: MOSI

Terminal Block Pins (NeoPixel, Button and Speaker)

On the front of the board is the terminal block for the special Prop-Maker pins: NeoPixels, button and speaker. On the back of the board, you can see the labels for each terminal block pin on the board silk.

• Neo - The external NeoPixel data output pin. Connect your NeoPixel strip's data input pin to this connection. It located on GPIO21 and can be accessed as EXTERNAL_NEOPIXELS in CircuitPython and PIN_EXTERNAL_NEOPIXELS in Arduino.
• G - Common ground for the external NeoPixels.
• 5V - 5V power for the external NeoPixels. This port provides high current drive from either the Feather LiPoly or USB port, whichever is higher. It is connected to a separate control transistor that is controlled by the External Power Pin described below. The External Power Pin is disabled by default, so you need to enable it in code to power the external NeoPixels.
• Btn - Extra digital input or output pin. It can be used for button input or digital output, for activation or a simple LED. It located on GPIO19 and can be accessed as EXTERNAL_BUTTON in CircuitPython and PIN_EXTERNAL_BUTTON in Arduino.
• + and - - Positive and negative speaker output connections from the I2S amplifier. You can drive any 4-8Ω speaker, up to 3 Watts. 

Additionally, there is a pin that lets you control the external NeoPixels, servo motor header and I2S amp for low power applications:

• External Power Pin - This pin is connected to a separate control transistor for the 5V terminal block pin, servo header and the I2S amplifier so that you can cut power to them for low power usage. It is located on GPIO23 and is accessed with EXTERNAL_POWER in CircuitPython and PIN_EXTERNAL_POWER in Arduino. It is disabled by default, so you will need to set the pin high to power the external NeoPixels, servo motor header pins and I2S amplifier.

Servo Connection

On the front of the board, to the left of the terminal block, are three 0.1" spaced header pins for connecting any hobby servo with three wires. The pins are labeled Servo on the board silk.

• Sig - Servo motor output pin. It located on GPIO20 and can be accessed as EXTERNAL_SERVO in CircuitPython and PIN_EXTERNAL_SERVO in Arduino.
• V+ - 5V power for the servo motor. This pin provides high current drive from either the Feather LiPoly or USB port, whichever is higher. It is connected to a separate control transistor that is controlled by the External Power Pin. The External Power Pin is disabled by default, so you need to enable it in code to power the external NeoPixels.
• G - Common ground for the external servo motor.

MAX98357 I2S Amplifier

On the front of the board, above the MISO and RX pins, is the MAX98357 I2S amplifier. It is a 3 Watt Class D audio amplifier that can drive any 4-8Ω speaker, up to 3 Watts. It communicates with the RP2040 via three pins:

• Data - Located on GPIO16. It can be accessed via I2S_DATA in CircuitPython and PIN_I2S_DATA in Arduino.
• Clock - Located on GPIO17. It can be accessed via I2S_BIT_CLOCK in CircuitPython and PIN_I2S_BIT_CLOCK in Arduino.
• Word Select - Located on GPIO18. It can be accessed via I2S_WORD_SELECT in CircuitPython and PIN_I2S_WORD_SELECT in Arduino.

To enable audio output from the amplifier, the External Power Pin needs to be enabled.

On the back of the board, above the RX and MI pins, are jumpers to adjust the I2S amp gain. The jumper pads are outlined on the silk and are labeled Amp Gain. The default gain for the amplifier is 9 dB

• To set the gain to 6 dB, solder the center jumper to the left jumper labeled 6. This connects the GAIN pin to V+.
• To se the gain to 12 dB, solder the center jumper to the right jumper labeled 12. This connects the GAIN pin to GND.

LIS3DH Accelerometer 

On the front of the board, to the right of the STEMMA QT connector, is the LIS3DH accelerometer. It is a triple-axis accelerometer with tap detection. You can use it for detection motion, tilt, or taps.

This accelerometer is connected over I2C on address 0x18. If you perform an I2C scan on this Feather with no other I2C devices connected, you will see this address. You can also use its interrupt pin to trigger for motion, tilt, taps, data ready, etc. The interrupt pin is connected to GPIO22 and can be accessed as ACCELEROMETER_INTERRUPT in CircuitPython and PIN_ACCELEROMETER_INTERRUPT in Arduino.

Microcontroller and Flash

The large square towards the middle is the RP2040 microcontroller, the "brains" of this Feather board.

The square towards the top-middle is the QSPI Flash. It is connected to 6 pins that are not brought out on the GPIO pads. It is used for program and data storage in Arduino and CircuitPython.

Buttons and RST Pin

The Boot button is the button on the right, located on GPIO7. It is available as board.BUTTON in CircuitPython and PIN_BUTTON in Arduino. It is also used to enter the bootloader. To enter the bootloader, press and hold Boot and then power up the board (either by plugging it into USB or pressing Reset). The bootloader is used to install/update CircuitPython.

The Reset button is on the left. It restarts the board and helps enter the bootloader. You can click it to reset the board without unplugging the USB cable or battery.

The Rst pin can be used to reset the board. Tie to ground manually to reset the board.

NeoPixel and Red LED

Above the pin labels for 24 and 25 is the status NeoPixel LED, labeled 4 on the board silk. It is connected to GPIO4. In CircuitPython, the NeoPixel is available at board.NEOPIXEL and the library for it is available in the bundle. In Arduino, it is accessible at PIN_NEOPIXEL. The NeoPixel is powered by the 3.3V power supply but that hasn't shown to make a big difference in brightness or color. In CircuitPython, the LED is used to indicate the runtime status.

Above the USB C connector is the D13 LED. This little red LED is controllable in CircuitPython code using board.LED, and in Arduino as PIN_LED.

STEMMA QT

In the middle of the board, to the left of the terminal block, is the STEMMA QT connector! This means you can connect up all sorts of I2C sensors and breakouts, no soldering required! This connector uses the SCL and SDA pins for I2C, which end up being the RP2040's I2C1 peripheral. In CircuitPython, you can initialize the STEMMA connector with board.STEMMA_I2C() (as well as with board.SCL board.SDA). In Arduino it is Wire.