4.2.1 Crystal

The SAM D21 Xplained Pro kit contains one crystal that can be used as clock source for the SAM D21 device. The crystal has a cut-strap next to it that can be used to measure the oscillator safety factor. This is done by cutting the strap and adding a resistor across the strap. More information about oscillator allowance and safety factor can be found in application note AVR4100.