Femto is an ultra-compact Raspberry Pi RP2040 module designed by Mirek Folejewski. Its four-layer board measures 12 × 12 mm and connects all 30 RP2040 GPIO pins, while carrying QSPI flash, a 12 MHz oscillator and a power LED. It is an open hardware design rather than a board with confirmed current retail availability, so building one may mean sourcing the components and having the published files fabricated and assembled.
What Femto is—and what “full-featured” means
Femto is a tiny module built around Raspberry Pi’s RP2040 microcontroller. The project’s stated goal is to make the smallest possible fully functional RP2040 module. Its 12 × 12 mm footprint packs in the microcontroller and supporting components, and all 30 GPIO pins are connected. Reset and BOOTSEL signals are also exposed through the module’s frame.
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Here, “full-featured” describes the module’s core hardware and connected GPIO, not a complete development board with convenient connectors. The separate solder frame and tester address the practical challenge of accessing signals on such a small board.
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Femto specifications
| Feature | Femto details |
|---|---|
| Microcontroller | Raspberry Pi RP2040 |
| Board footprint | 12 × 12 mm |
| GPIO | All 30 pins connected |
| Flash | Onboard QSPI flash in a USON8 package. CNX Software reported a 4–64 Mbit range for Femto variants in 2022. |
| Clock component | 12 MHz oscillator/crystal |
| PCB | Four layers |
| Other onboard parts | Decoupling components and a power LED |
| Control signals | Reset and BOOTSEL exposed through the frame |
The RP2040 itself is a dual-core Cortex-M0+ microcontroller rated to run at up to 133 MHz, with 264 kB of SRAM, according to CNX Software’s 2022 coverage. Those are MCU specifications, not a claim that Femto’s design changes the chip’s capabilities.
#1 Best Overall
- The Raspberry Pi Pico is a beginner-friendly microcontroller board that uses MicroPython to give you a taste of the Internet of Things and microcontrollers. The RP2040 is a well-designed microprocessor that can be utilized in almost any Internet of Things project. It has enough power to complete the task quickly.
- 【Raspberry Pi RP2040 Microcontroller】Raspberry Pi Pico features Dual-core ARM Cortex M0+ processor, flexible clock running up to 133 MHz. With 264KB of SRAM, and 2MB of on-board Flash memory.Supports up to 16 MB of off chip flash memory via a dedicated QSPI bus
- 【Multiple Software Support】Pico has rich and complete software support, it comes with a complete Rasberry Pi official C/C++ SDK, Micropython SDK.The programming and burning of Pico need to be carried out on the computer. Supported operating systems and computers include:Raspberry Pie with Raspberry Pi OS,Other platforms equipped with Debian based Linux system Computer with MacOS, Computers with Windows, etc.
- 【Rich Hardware Interface】Raspberry Pi Pico has 30 GPIO pins, 4 pins for analog signal input and 26 × multi-function GPIO pins, 2 × SPI, 2 × I2C, 2 × UART, 3 × 12-bit ADC, 16 × controllable PWM channels.USB 1.1 supported by host and device, The installation mode can be flexibly selected by users to facilitate welding with other development boards.
- 【Build Project in Tiny Size】Only 2.1cm*5.1cm ( as small as your thumb). Pico has been designed to use either soldered 0.1" pin-headers or can be used as a surface-mountable 'module'.
Why the module includes a frame and tester
A 12 mm square module is space-efficient, but its tiny form factor makes its signals less convenient to reach than those on a conventional development board. Femto’s project therefore includes a solder frame to make the I/O more usable, as well as a tester for functional checks.
Hackster reports that the Femto Tester brings GPIO pins to onboard LEDs and provides USB Type-C for power and data. It also has dedicated BOOTSEL and reset buttons. The setup makes it possible to check GPIO activity and control the module without treating the bare module as a plug-in development board.
Rank #2
- DUAL-CORE PERFORMANCE & MEMORY: Features the RP2040 microcontroller chip with a dual-core ARM Cortex M0+ processor running at a flexible clock speed up to 133 MHz. Equipped with 264KB of on-chip SRAM and 2MB of on-board Flash memory, providing ample space for complex code and data storage. Includes an on-chip accelerated floating point library for demanding calculations.
- VERSATILE I/O & PERIPHERALS: Provides access to 29 GPIO pins from the RP2040 chip (20 accessible via pin headers, others via soldering). Features a rich set of peripherals including 2x SPI, 2x I2C, 2x UART, 4x 12-bit ADC, and 16 controlled PWM channels. Supports USB1.1 host and device modes for flexible connectivity and communication.
- CUSTOM PERIPHERALS & POWER MODES: Includes 8 programmable I/O (PIO) state machines, allowing for the creation of custom peripheral support beyond standard hardware. Supports low-power sleep and hibernation modes, making it suitable for battery-powered applications. Programming is simplified with drag-and-drop file transfer via USB mass storage recognition.
- COMPACT FORM & EASY INTEGRATION: Features a stamp hole design allowing the board to be directly soldered onto a user-designed backplane for compact and robust integration into custom projects. Includes an accurate on-chip clock, timer, and a temperature sensor. The pins arrive unsoldered, offering flexibility for either direct mounting or use with the included pin headers.
- COMPLETE 6-PACK SET & SUPPORT: Includes 6 x RP2040-Zero Microcontroller Boards and 6 x Pin Header Sets. Digital documentation and technical support for setup, programming, and troubleshooting are available through our store customer service.
How Femto compares in size
The project compares Femto with two larger RP2040 boards. The measurements below are the approximate footprints cited by the project, not a comparison of features or performance.
| Board | Approximate footprint |
|---|---|
| Femto | 12 × 12 mm |
| Raspberry Pi Pico | 51 × 21 mm |
| Solder Party RP2040 Stamp | 25 × 25 mm |
Femto’s smaller footprint favors designs where board area is especially constrained. The trade-off is physical access: the solder frame or a custom carrier is a more practical way to connect the module’s signals than handling the tiny board on its own.
Rank #3
- DUAL-CORE PERFORMANCE & MEMORY: Features the RP2040 microcontroller chip with a dual-core ARM Cortex M0+ processor running at a flexible clock speed up to 133 MHz. Equipped with 264KB of on-chip SRAM and 2MB of on-board Flash memory, providing ample space for complex code and data storage. Includes an on-chip accelerated floating point library for demanding calculations.
- VERSATILE I/O & PERIPHERALS: Provides access to 29 GPIO pins from the RP2040 chip (20 accessible via pin headers, others via soldering). Features a rich set of peripherals including 2x SPI, 2x I2C, 2x UART, 4x 12-bit ADC, and 16 controlled PWM channels. Supports USB1.1 host and device modes for flexible connectivity and communication.
- CUSTOM PERIPHERALS & POWER MODES: Includes 8 programmable I/O (PIO) state machines, allowing for the creation of custom peripheral support beyond standard hardware. Supports low-power sleep and hibernation modes, making it suitable for battery-powered applications. Programming is simplified with drag-and-drop file transfer via USB mass storage recognition.
- COMPACT FORM & EASY INTEGRATION: Features a stamp hole design allowing the board to be directly soldered onto a user-designed backplane for compact and robust integration into custom projects. Includes an accurate on-chip clock, timer, and a temperature sensor. The pins arrive unsoldered, offering flexibility for either direct mounting or use with the included pin headers.
- COMPLETE 3-PACK SET & SUPPORT: Includes 3 x RP2040-Zero Microcontroller Boards and 3 x Pin Header Sets. Digital documentation and technical support for setup, programming, and troubleshooting are available through our store customer service.
Where to find the design and manufacturing files
The project repository publishes design and production materials for reproducing the module, including KiCad and Altium sources, Gerber files, pick-and-place data, a bill of materials and assembly files. It also includes a Python test script for using the Femto Tester through the Thonny IDE. The repository identifies JLCPCB as a destination for its manufacturing files; that does not establish a particular current price or service arrangement.
- Open the Femto project repository and review its design and manufacturing files.
- Use the bill of materials and assembly data to plan component sourcing and fabrication. Check the current files and component availability before ordering.
- For functional checks, connect the module to the Femto Tester and use the project’s Python script through Thonny IDE.
Can you buy an assembled Femto module?
The project repository documents an open design and fabrication files, but does not establish a current retail seller, price or stock status for preassembled Femto modules. Verify any seller listing directly before relying on it. If no assembled module is available, the published production files offer a route to having boards fabricated and assembled.
Rank #4
- DUAL-CORE PERFORMANCE & MEMORY: Features the RP2040 microcontroller chip with a dual-core ARM Cortex M0+ processor running at a flexible clock speed up to 133 MHz. Equipped with 264KB of on-chip SRAM and 2MB of on-board Flash memory, providing ample space for complex code and data storage. Includes an on-chip accelerated floating point library for demanding calculations.
- VERSATILE I/O & PERIPHERALS: Provides access to 29 GPIO pins from the RP2040 chip (20 accessible via pin headers, others via soldering). Features a rich set of peripherals including 2x SPI, 2x I2C, 2x UART, 4x 12-bit ADC, and 16 controlled PWM channels. Supports USB1.1 host and device modes for flexible connectivity and communication.
- CUSTOM PERIPHERALS & POWER MODES: Includes 8 programmable I/O (PIO) state machines, allowing for the creation of custom peripheral support beyond standard hardware. Supports low-power sleep and hibernation modes, making it suitable for battery-powered applications. Programming is simplified with drag-and-drop file transfer via USB mass storage recognition.
- COMPACT FORM & EASY INTEGRATION: Features a stamp hole design allowing the board to be directly soldered onto a user-designed backplane for compact and robust integration into custom projects. Includes an accurate on-chip clock, timer, and a temperature sensor. The pins arrive unsoldered, offering flexibility for either direct mounting or use with the included pin headers.
- COMPLETE 12-PACK SET & SUPPORT: Includes 12 x RP2040-Zero Microcontroller Boards and 12 x Pin Header Sets. Digital documentation and technical support for setup, programming, and troubleshooting are available through our store customer service.
For the core chip, Raspberry Pi maintains official RP2040 documentation and datasheet resources. The RP2040 is the microcontroller used in Femto; a chip alone is not a substitute for the module’s PCB, flash, oscillator and supporting components.
Open hardware status and licensing
The Open Source Hardware Association registry lists Femto as version v1, UID PL000009, certified September 7, 2022. Its registry entry records CERN-OHL-1.2 for hardware, CC BY-SA for documentation, and no software license. The project repository also describes Femto as open-source hardware and links to the certification. Consult the repository and registry terms when reusing or modifying the files.
Quick Recap
Best Value
- Support C/C++, MicroPython, complete SDK, open source materials tutorial, easy to use, can be quickly embedded in applications
- Dual-core Arm Cortex M0+ processor, flexible clock running up to 133 MHz
- 264KB of SRAM, and 2MB of on-board Flash memory;USB-C connector, keeps it up to date, easier to use
- Castellated module allows soldering direct to carrier boards; USB 1.1 with device and host support
- Low-power sleep and dormant modes; Drag-and-drop programming using mass storage over USB
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