So, I just found out that I designed my board with a 32.768 kHz crystal
connected to the XTAL pins, rather than the TOSC pins. The problem is that to
move it, I lose my only available SPI port (this is an ATxmega256A3U, and all
the other SPI port pins are being used for something else).
The easiest solution will be to use a MHz-speed crystal instead of a 32 kHz
crystal. I don't need low power operation. But I'm not sure I can calibrate the
internal oscillators via DFLL using an external crystal; the docs talk about
external clock.
There doesn't seem to be a way to drive the RTC from the XTAL pins, nor can you
calibrate the internal 32 kHz clock from an external crystal (on XTAL1 & 2).
I don't really need RTC.
So, I guess the best thing is to just stick a 16 MHz crystal on the XTAL pins
and be done with it? I need USB. If I understand things correctly, I can PLL
that up to 96 MHz, then divide by 2 to get 48 MHz.
If I'm wrong, please let me know.
Thank you!