i used regular crystal but operation was very flaky. long leads or anything nearby caused it to stop oscillating.
imo this chip is a piece of crap.
you will find there is no full swing option anymore. only low power mode now. it is a radical departure from most other avr.
The "full swing oscillator" option has been removed from a bunch of the other ATmega chips recently as well;
When using ATmega328PB and mapping those extra pins, this is probably a good opportunity to map PB7/XTAL2 and use that as a regular I/O pin, and make the standard thing to do use an oscillator instead of a crystal.
It is OK that an oscillator does not cost the same as a clod of dirt like a crystal does, because you're enjoying the extra pins and various other additional features.
what other advantages are there?
I see there are oscillators with pads on the bottom that also wrap part way up the side. I think that would be my selection for hand soldering. A little flux and pre-tinned pads and should be fine. This processor will require the hobbyist to get comfortable with SMD anyway, since a DIP version is not available.
$1 per pin for that one extra pin, and all those other pins are practically free! Think of it as a special buy.
I think a PB Pro Mini version may be interesting just for the extra serial port pins, even if none of the other new pins are brought out to headers. And the Pro Mini would probably be fine with a regular crystal, because of the short clock leads. I have not yet bought one of these MCUs to try out. I might find it crappy like john1993 does, or I might like it.
I guess the only advantage I can think of is getting to use the ATmega328PB reliably and so john1993 can have his foot-long clock leads. :-)
Then I attempted to upload a sketch using FTDI, no dice.
FWIW, a standard Optiboot at 57600bps works fine on an Atmel 328PB Xplained Mini eval board. It doesn't do 115200, because the mEDBG chip apparently doesn't use the U2X mode on its uart. And putting the bootloader ON to the Xplained mini (through the mEDBG) still seems to require Atmel Studio.