• VB (VBUS) - This is the micro-USB input voltage, connected to the micro-USB port on the Raspberry Pi Pico. It is nominally 5V.
• VS (VSYS) - This is the main system input voltage. It can range from 1.8V to 5.5V and is used to generate the 3.3V needed for the RP2040 and the GPIO pins.
• EN (3V3_EN) - This connects to the enable pin on the Raspberry Pi Pico, and is pulled high (to VSYS) via a 100kΩ resistor. The slide switch at the bottom right edge of the Tripler is connected to this pin.
• 3.3V - This is the 3.3V output from the Raspberry Pi Pico. There is a long strip of connected holes for 3.3V power, noted by a line of white on the board silk.
• VREF (ADC_VREF) - This is the ADC power supply and reference voltage. It is generated on the Raspberry Pi Pico by filtering the 3.3V supply. It can be used with an external reference when ADC performance is required.
• GND - This is the common ground for power and logic. All GND pins are highlighted in white rectangles on the silk.

• LiPoly connector/charger - You can plug in any 500mAh or larger 3.7V/4.2V single-cell battery into the JST 2-PH port with the correct polarity to both power your Pico and charge the battery. The battery will charge from the USB power when USB is plugged in. If the battery is plugged in and USB is plugged in, the Pico will power itself from USB and it will charge the battery up.
• Orange Indicator LED - To the right of the JST 2-PH port is the orange charge indicator LED. When the battery is charging, the orange LED will be lit. When charging is complete, the LED will turn off. If there's no battery plugged in while the board is powered by USB, the LED may be dimly lit - this is expected!
• Green Indicator LED - To the left of the JST 2-PH port is the green charge indicator LED. While a battery is charging, the green LED will be off. When the battery is fully charged, or If there's no battery plugged in, the green LED will be lit.

• Charge Rate Jumper - On the back of the Tripler is the charge rate jumper. It is labeled Cut for 250mA on the board silk. By default the charge rate is 500mA for use with 500mAh+ sized batteries. You can cut a jumper to reduce the charge rate to 250mA if using 250mAh to 500mAh battery. Batteries that are smaller than 250mAh are not supported.
• Alkaline/NiMH Battery Pack Jumper - On the back of the Tripler is the alkaline/NiMH battery pack jumper. It is labeled Chg En on the board silk. If you cut this jumper, it will disconnect the charger circuitry completely from the JST 2-PH port. This means you can use 3xAA or 3xAAA battery packs for alkaline or NiMH battery usage.

• SCL - I2C clock pin on the PiCowBell. It is connected to your Pico I2C clock line, which is GPIO5. This connection is shared with the STEMMA QT port and the EYESPI connector on the board.
• SDA - I2C data pin on the PiCowBell. It is connected to your microcontroller I2C data line, which is GPIO4. This connection is shared with the STEMMA QT port and the EYESPI connector on the board.
• STEMMA QT - These connectors allow you to connect to dev boards with STEMMA QT connectors or to other things with various associated accessories. The port is located on the end of the PiCowBell.
• STEMMA QT Breakout Holes - There is an extra set of 4 breakout holes directly below the STEMMA QT port if you want more I2C connections or want to re-assign the I2C port.

At the top of the board in the middle section is one RGB NeoPixel LED. Its data pin is connected to GPIO AD2. There is a jumper below it labeled AD2. You can cut this jumper to disconnect the NeoPixel from AD2.

At the bottom of the board, opposite the STEMMA QT port, is the EYESPI connector. This connector allows you to connect EYESPI-compatible displays using an EYESPI cable, with no soldering or jumper wires needed. The EYESPI pins are connected to the following GPIO:

• Vin - 3.3V
• Backlight - AD0
• GND - GND
• MISO - GPIO16
• MOSI - GPIO19
• SCK - GPIO18
• Display CS - GPIO21
• DC - GPIO20
• INT - GPIO22
• SDA - GPIO4
• SCL - GPIO5
• Touchscreen CS - GPIO15
• SD card CS - GPIO17

The PiCowbell has three sets of two 2x20 slim socket headers to plug in your Pico and have extra rows of sockets for each pin. On the second and third sets of headers you can plug in an accessory for your Pico. There are also duplicate hole pads next to each pin for solder-jumpering:

• IO0-IO15, IO16-IO22, Reset, A0-A2, VR, 3V, EN, VS and VB. Ground pins that have a duplicate hole pad are highlighted in white rectangles on the board silkscreen.

Between the sets of socket headers, you'll find the proto areas. These areas on the board are made up of 12 3 hole-connected strips on the left and in the middle, and 11 3 hole-connected strips on the right. You can cut the traces between the holes, but they're intended to be treated like mini-mini breadboards.

At the bottom edge of the board in the middle section is the reset button. It is routed to the reset pin on the PiCowbell and is labeled RESET on the board silk. You can press it to restart your program.

At the bottom right edge of the board is the enable switch. It is routed to the enable pin on the PiCowbell and is labeled Enable on the board silk. Moving the switch to the Off position will disable the 3.3V power supply. Moving the switch to the On position will enable the 3.3V power supply. The switch does not disconnect USB power. Disabling 3.3V is as close as we can get to 'turning off' the Pico.