The ATmega4809 Curiosity Nano board has a 32.768 kHz crystal mounted.
The crystal is connected to the ATmega4809 by default, but the GPIOs are routed out to the edge connector through not mounted resistor footprints. The two I/O lines routed to the edge connector are disconnected by default to both reduce the chance of contention to the crystal as well as removing excessive capacitance on the lines when using the crystal. To use the pins PF0 and PF1 as GPIO on the edge connector, some hardware modification is needed. Solder a 0 Ω resistor or add a solder blob to the footprints to connect the routing. The crystal should be disconnected when using the pin as GPIO, as this might harm the crystal.
The 32.768 kHz crystal on ATmega4809 Curiosity Nano is a Kyocera Corporation ST3215SB32768C0HPWBB 7 pF crystal.
The crystal has been formally tested and matched to the ATmega4809 by Kyocera. The test report is available in the design documentation distributed with this document for ATmega4809 Curiosity Nano.
| ATmega4809 Pin | Function | Shared Functionality |
|---|---|---|
| PF0 | TOSC1 (Crystal input) | Edge connector |
| PF1 | TOSC2 (Crystal output) | Edge connector |
