smôl Header Hookup Guide

Contributors: PaulZC
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smôl is a new board format and, as the name suggests, they're really small!

smôl Header

smôl Header


Need to do some prototyping with smôl? Or want to connect your smôl stack to a Qwiic board or your favorite SPI sensor? The smôl Header is the perfect solution!

Required Materials

If you want to connect a Qwiic board to your smôl stack, you're going to need some Qwiic cables:

SparkFun Qwiic Cable Kit

SparkFun Qwiic Cable Kit

Qwiic Cable - 50mm

Qwiic Cable - 50mm

Flexible Qwiic Cable - Female Jumper (4-pin)

Flexible Qwiic Cable - Female Jumper (4-pin)

Qwiic Cable - Breadboard Jumper (4-pin)

Qwiic Cable - Breadboard Jumper (4-pin)


If you're prototyping with smôl, you may need:

Break Away Headers - Straight

Break Away Headers - Straight

Breadboard - Classic

Breadboard - Classic

Jumper Wires Premium 6" M/M Pack of 10

Jumper Wires Premium 6" M/M Pack of 10

Breadboard - Mini Modular (Red)

Breadboard - Mini Modular (Red)


The Header is part of the smôl ecosystem. Why not pair it with one of the smôl Processor Boards?

smôl ESP32

1 Retired

To be able to reduce the sleep current below 10µA, you're going to want to pair the ESP32 with one of our intelligent smôl Power Boards:

smôl Power Board LiPo

smôl Power Board LiPo

smôl Power Board AAA

smôl Power Board AAA


Don't forget that you will need Flexible Printed Circuits to connect your smôl boards together. You're going to need one FPC per board. Our 36mm FPC is the perfect length if you want the smôl boards to stack neatly, one on top of the other.

smôl 36mm 16-way Flexible Printed Circuit


Suggested Reading

This is the hookup guide for the smôl Header. Click the button below if you want to find out more about smôl itself.

We recommend taking a look through the following tutorials if you are not familiar with the concepts covered in them:

Serial Peripheral Interface (SPI)

SPI is commonly used to connect microcontrollers to peripherals such as sensors, shift registers, and SD cards.


An introduction to I2C, one of the main embedded communications protocols in use today.

Hardware Overview

smôl boards are designed to stack one on top of the other, using 16-way 0.5mm-pitch Flexible Printed Circuits (FPCs). We really like FPCs and we're using them on more and more of our products. But they can be a bit tricky when it comes to prototyping or if you want to connect other devices to your smôl stack. The smôl Header is here to help!

FPC Connections

Like all of our smôl boards, the Header is equipped with a 16-way 0.5mm-pitch Flexible Printed Circuit connector. The pin-out for the smôl Header connector is as follows:

Connector Pin No.Signal NameFunction
1PROC_PWR_ENProcessor Power Enable
23V33.3V Power Rail
3GNDPower Ground / 0V
5COPISPI Controller Out Peripheral In
6CIPOSPI Controller In Peripheral Out
7CS0SPI Chip Select 0
8CS1SPI Chip Select 1
9CS2SPI Chip Select 2
10GPIO0General Purpose Input / Output 0
11GPIO1General Purpose Input / Output 1
12SDAI2C Data
13SCLI2C Clock
14GNDPower Ground / 0V
153V33.3V Power Rail
16V_USBUSB Power Rail (5V)

Breakout Pins

You've got full access to all the smôl pins, so connecting your favorite SPI board to smôl is as easy as plug-and-play! The smôl Header breaks out all 16 smôl connections in good old 0.1" format. The hole pattern is the same as an old school 16-pin 0.3" Dual-In line Package (DIP). Perfect for soldering header pins to and then pushing into standard breadboard.

Pictured are the 16 header breakout pins

Pictured are the dimensions of the breakout pins

Qwiic Connector

We've included a Qwiic connector too, so you can attach your favorite Qwiic boards to your smôl stack qwiicly and easily.

Pictured is the header Qwiic connector

Qwiic (I2C) Pull-ups

The Header also includes pull-up resistors for the I2C SDA and SCL signals. You can disconnect the resistors if required by opening the dual split-pad jumper links.

Pictured are the two pull-up resistors and the split pad jumper links

If you haven't used jumpers before, please check out our tutorial.

How to Work with Jumper Pads and PCB Traces

Handling PCB jumper pads and traces is an essential skill. Learn how to cut a PCB trace, add a solder jumper between pads to reroute connections, and repair a trace with the green wire method if a trace is damaged.


Not working as expected and need help? SparkX products are rapidly produced to bring you the most cutting edge technology as it becomes available. These products are tested but come with no guarantees. Live technical support is not available for SparkX products. Head on over to our forum for support or to ask a question and we will get back to you as soon as we can.

Resources and Going Further

For more information about the smôl Header, check out the following links:

smôl Header Documentation:

smôl Documentation: