The SAM C21 Xplained Pro kit contains one mounted 32.768kHz crystal and a footprint for higher frequency crystals that can be used as clock sources for the SAM C21. The crystals have cut-straps next to them that can be used to measure the oscillator safety factor. This is done by cutting the strap and adding a resistor across the strap. Information about oscillator allowance and safety factor can be found in appnote AVR4100. Information about clock calibration and compensation can be found in appnote AT03155.
The footprint for the external crystal is based on the Epson® TSX-3225 series.
| SAM C21 pin | Function | Shared functionality |
|---|---|---|
| PA00 | XIN32 | - |
| PA01 | XOUT32 | - |