Epi 32U4 is a tiny, Arduino-compatible, USB-Type-C dev board powered by the ATmega32U4 microcontroller. We’ve designed it to be as small as practically possible, and it provides quite a few protective features to keep it operating well in noisy environments. That includes a fuse and ESD protection as well as a ferrite bead and a low-pass filter for analog reference in case the power supply is noisy.

Epi 32U4’s diminutive size allows you to incorporate it into just about any project. You can solder it directly to a PCB or use the included headers for a less permanent mounting solution. It is also quite easy to hand wire, as it includes mounting slots that allow you to screw it down before you begin soldering.

Epi 32U4 can act as a USB device, which makes it ideal for projects like compact keyboards, and its Type-C connector helps you future-proofs your designs. It also has more available IO ports than a standard Pro Micro, so it’s appropriate even for projects where space is not at a premium. Finally, its USB D+ and D- lines are broken out, in case your design requires a separate connector.

Features & Specifications

ATmega32U4
16-MHz crystal
Runs at 4.5 - 5.5 V for the 16 MHz version, down to 2.7 V at 8 MHz
Castellated pins at 1.27-mm spacing
ESD and surge protection on USB data lines and power input
500-mA polyfuse
Ferrite bead for power filtration
Low-pass filter for analog voltage reference
24 available IOs
Protruding USB Type-C port with mounting slots beside it
LED on pin 13
Made in the EU

Comparisons

	Epi 32U4	Pro micro	Elite-C V4	Qwiic Pro micro	µduino	Beetle	PICO
Manufacturer	Ping Hobbyelektronik	Various	Keeb	Sparkfun	µduino	DFrobot	Mellbell
Footprint	22.75 x 12.75 mm	33 x 17.75 mm	33 x 17.75 mm	33 x 17.75 mm	12 x 12 mm	20 x 22 mm	15.25 x 15.25 mm
USB Type-C	Yes	No	Yes	Yes	No	No	No
Castellated pins	Yes	No	Yes	Yes	No	Arguably	No
IO available	24	21	24	21	20	10	12
Voltage regulator	No	Yes	No	Yes	Yes	No	Yes
Protective features	Several ¹	None	None	None	Some ²	None	None
Screw mounting	Yes	No	No	No	No	No	No
Open Source	Yes	Yes	Unclear	Yes	Somewhat	Unclear	Unclear
Availability	Available	Plentiful	Available	Available	Unavailable	Available	Unavailable
Price	$25	$5+	$18	$21.50	$23	$9	$17

¹ Varistors for ESD and surge protection, a ferrite-bead power filter, and a low-pass filter for analog voltage reference.
² A low-pass filter for analog voltage reference.

Size Comparisons

Pinout Diagram

Support & Documentation

You can find source and documentation files for Epi 32u4 in our GitHub repository. The data sheet and KiCad files are available there as well.

Manufacturing

Epi 32U4 is assembled in Sweden, where we populate German-made PCBs with high-quality components from well-known manufacturers using an open-source Lumen PnP machine. We test each unit in our laboratory.