Epi 32U4 is an Arduino-compatible, ATmega32U4-based microcontroller board with a pinout based on the Pro Micro. All pins are broken out to castellated holes with 1.27-mm spacing. We designed Epi 32U4 to accommodate noisy environments—even without voltage regulators—thanks to a ferrite power filter, a fuse, ESD protection, and surge protection. With an ATmega32U4 at its core, it can act as a USB device, which makes it perfect for keyboards and other space-constrained projects that require a compact controller.

Features & Specifications

ATmega32U4
16-MHz crystal
Runs at 4.5 - 5.5 V
Castellated pins at 1.27 mm spacing
ESD and surge protection on USB data lines and power input
500 mA polyfuse and ferrite bead for power filtration
23 available IOs
Portruding 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	23	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	Soon	Plentiful	Available	Available	Unavailable	Available	Unavailable

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.

Pinout Diagram

Made by Rasmus at Ping Hobbyelektronik using Paul Tol's muted, colorblind-safe palette CC-BY 4.0 2023

Open Source

You can find source files for Epi 32U4 in our GitHub repository. Source files for the previous version are also available.

Interested in This Project?

You can sign up at the top of this page to be notified when the campaign launches and to receive other updates. We work hard to ensure that only useful information is sent out, and you can unsubscribe at any time.