The Adafruit Proto Under Plate PiCowBell is intended to be treated like a mini solderless proto plate to simplify programming and sensor connectivity for your Raspberry Pi Pico board. Reset button? Yes! STEMMA QT / Qwiic connector for fast I2C? Indeed. Plug-and-play so no soldering necessary when used with a Pico H or Pico WH? Here you go!

This board has double sockets already soldered on, you can plug in your Pico board directly in, and get access to a prototyping area underneath as well as a second row of socket pins. The second row means you can connect wires just by poking them into the header, either directly to LEDs or buttons or to jumper to a breadboard. So you don't have to look up or count pins, each socket is nicely labeled. There's also 4 mounting holes for easy attachment to an underplate.

The dual socket headers we use are 'hollow' - that means you can connect through the back if desired. Specifically, you can use Pico Stacking Headers to plug through to some other device that is expecting Pico pins. Also, in theory, if you soldered pin headers on the 'wrong side' of a Pico, you could plug it up through the bottom.

We recommend picking up a set of little rubber feet to protect your desk if you're not mounting this board to something else.

The Proto Under Plate PiCowBell provides you with the following:

• 2x20 slim socket headers - plug in your Pico and have an extra row of sockets for each pin!
• Right angle reset button that sticks out the end.
• Right angle JST SH connector for I2C / Stemma QT / Qwiic connection. Or can use it for plain GPIO wiring if you don't have any I2C devices to attach. Provides 3V, GND, IO4 (SDA), and IO5 (SCL).
  There is an extra set of 4 breakout holes next to the JST SH if you want more I2C connections or want to re-assign the I2C port.
• 3 hole-connected strips are in the center area. You can cut the traces between the holes, but they're intended to be treated like a mini-mini breadboard.
• Every pad on the Pico has a duplicate hole pad next to it for solder-jumpering.
• The ground pads have white silkscreen rectangles to easily identify, plus one long ground strip near the reset button.
• One long strip of connected holes for 3.3V power.
• Gold-plated pads for easy soldering.

We do not have I2C pullups on the board, but your Qwiic/QT breakout board or accessory likely already has them onboard. If using the Philhower Arduino core, the Wire peripheral is already set up to use IO4 and IO5. If using CircuitPython or MicroPython, you'll need to let the code know to look at 4+5 for SDA+SCL pins.

Power

• 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.
• 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.

I2C Logic

• 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 on the end of 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 on the end of 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.

Socket Headers and Duplicate GPIO Hole Pads

The PiCowBell has two 2x20 slim socket headers to plug in your Pico and have an extra row of sockets for each pin. 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.

Proto Area

In the center of the board, you'll find the proto area. This area on the board is made up of 12 3 hole-connected strips. You can cut the traces between the holes, but they're intended to be treated like a mini-mini breadboard.

Reset Button

At the bottom edge of the board 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.

Files

• EagleCAD PCB files on GitHub
• 3D Models on GitHub
• Fritzing object in the Adafruit Fritzing Library

Schematic and Fab Print