Mirek Folejewski's Femto Module Is a Full-Feature Raspberry Pi RP2040 in the Smallest Footprint Yet

Hardware designer Mirek Folejewski has built what could well be the smallest Raspberry Pi RP2040 module around, a tiny 12×12mm (0.47×0.47") gadget dubbed the Femto module.

"Femto is a ultra compact RP2040 module," Folejewski explains of the design, which boasts a footprint only marginally larger than the Raspberry Pi RP2040 microcontroller chip around which it is built. "The project consists of three parts: Module (mainboard); frame (solder frame); tester (testbench, only for functional verification)."

Created on a four-layer PCB, the board design breaks out all 30 general-purpose input/output (GPIO) pins of the dual-core RP2040 and still finds room for a USON8-packaged qSPI flash module, a 12MHz crystal oscillator, and a status LED to indicate power.

To make confirming successful assembly of the compact module easier, Folejewski's Femto Tester serves as a carrier board: With the Femto module connected at its center, it brings all GPIO pins out to on-board status LEDs and provides USB Type-C connectivity for power and data plus dedicated boot-select and reset buttons.

The Femto module isn't the only small-footprint surface-mount module designed around the RP2040 microcontroller: Last year Solder Party unveiled the RP2040 Stamp, which as the name implies is a stamp-sized RP2040 module. Compared to the Femto Module, though, the RP2040 Stamp is a behemoth — albeit one that makes accessing the pins of the RP2040 easier.

Folejewski has released the design files for the boards in KiCad and Altium formats on the project's GitHub repository, along with Gerber, assembly, pick-and-place, and bill-of-materials files for manufacturing. The maker has confirmed that they are open source hardware, but has not specified under which license the designs are made available.