2) allow different output voltages for two of the four
banks of the Silabs chip
https://osmocom.org/issues/3905
I'd use the DAC for software voltage tuning.
Use 0R to select which bank uses which (default rail or programmable
one, with just default to have 1/2 bank being the programmable vio).
3) should we keep the VCTCXO?
No. As you explained I think it's better to split functions and not
overload this board.
4) Use SAMD XOSC / PLL / GCLK to allow lower reference
frequencies
https://osmocom.org/issues/3857
Where we'd actually use one of the SAMD GCLK outputs as one of the
intputs to the Si5351C, and expose a GCLK input of the SAMD on an
external header. This way, much lower frequencies can be used to
driver the Si5351C. Or one could even go for deriving them from the
SAMD RTC XTAL.
Does that mean the SAMD core would be running from the reference clock
? (and so wouldn't run if there is no reference connected)
Cheers,
Sylvain