Small SAMD21 breakout

This is a small, simple breakout for the Microchip (formerly Atmel) ATSAMD21E series of chips in the TQFP package. I designed it mostly for something to do while locked down at home, but also so that I could use the bare ICs I had spare from previous projects.

Most I/O pins are broken out, with the exception of PA00/01 (XIN32 and XOUT32 for the watch crystal) and PA24/25 (D- and D+ for USB). The SWD interface is available via either the header, or through the SOICbite connector opposite the USB footprint. There's an onboard regulator, crystal, reset button, and USB jack make things a bit more convenient.

This design is based on Adafruit's Trinket M0 as well as Technoblogy's Minimal ATSAMD21 Computer.

BoM

Reference	Quantity	Value	Footprint
C1, C2	2	10 μF, > 6 V	0603
C3, C4	2	1 μF, > 4 V	0603
C5	1	0.1 μF, > 4 V	0603
C6, C7	2	10 pF, > 4 V	0603
J1	1	Micro-USB jack	Molex 105017-0001
SW1	1	Push switch	Alps SKRKAEE020
U1	1	AP2112K-3.3	SOT23-5
U2	1	ATSAMD21Exx	TQFP-32
Y1	1	32.768 kHz, < 12.5 pF load	Micro Crystal CM7V-T1A

Schematic