issues.
- atusd/ERRATA: work around the clock instability by replacing the
resistive divider with a capacitative divider
- atusd/ERRATA: a ground plane under the clock circuit would also be good to
have
- atusd/ERRATA: via near pin 1 is too close to the chip if we need to cut
wires (in DIY boards)
- atusd/sim/cdiv.sch: simulation of the capacitative divider
