The Seeedstudio XIAO SAMD21 is a small board with 14 pins that is highly compatible with Arduino’s SAMD21 based microcontroller boards (Nano 33 IoT, Zero, and the MKR series of boards). It contains only the microcontroller, a crystal oscillator (which the Nano 33 IoT does not have), voltage regulator and a “modern” USB-C connector for …
A friend of mine, David Sparks, is using a SAMD based board (a Seeedstudio XIAO) to be a real time clock. You can see his project here: https://github.com/IowaDave/SAMD21-RTC-Clock. The SAMD has a Real Time Counter which can be configured as a Real Time Clock (RTC=RTC!) eliminating the need for a second component. However when run …