If you're ready to step your (compatible with) Arduino game up from older 8-bit/16MHz microcontrollers, the SparkFun SAMD21 Dev Breakout is a great landing spot. The SparkFun SAMD21 Dev Breakout is an (compatible with) Arduino-sized breakout for the Atmel ATSAMD21G18, a 32-bit ARM Cortex-M0+ processor with 256KB flash, 32KB SRAM, and an operating speed of up to 48MHz. This dev breakout provides you with a hardware option that solves the problems of low storage limits and dynamic memory stack overflows that have plagued the previous iterations. The SparkFun SAMD21 Dev Breakout has been equipped with a USB interface for programming and power, surrounded with an RTC crystal, and a 600mA 3.3V regulator. By utilizing the Pro R3's extra PCB real-estate we've been able to leave room for a few extra GPIO pins and an integrated LiPo charger. To power the SAMD21 Breakout board, just plug it into a USB port on your computer via the micro-B port on the breakout. Not near a USB port? No problem, the SparkFun SAMD21 Dev Breakout is also equipped with a LiPo Battery connector (for a single-cell 3.7-4.2V litium-polymer battery) and unpopluated supply input to solder on your own PTH Barrel Jack (please be aware that the 3D model that we have on file does show a barrel jack attached, this is only for dimensional use since this breakout does not come with one attached).
If you've used any (compatible with) Arduino before, this pinout shouldn't surprise you – the layout meets the 1.0 footprint standard, including a separate SPI header and additional I2C header. One of the most unique features of the SAMD21 is SERCOM – a set of six configurable serial interfaces that can be turned into either a UART, I2C master, I2C slave, SPI master, or SPI slave. Each SERCOM provides for a lot of flexibility: the ports can be multiplexed, giving you a choice of which task each pin is assigned.