The sam0 MCUs all have a DAC peripheral.
The DAC has a resulution of 10 or 12 bits and can have one or two
output channels.
The output pins are always hard-wired to PA2 for DAC0 and PA5 for DAC1
if it exists.
On the same54-xpro I would only get a max value of ~1V when using the
internal reference, so I configured it to use an external voltage reference.
The external reference pin is hard-wired to PA3, so you'll have to connect
that to 3.3V to get results.
