[Balloon] Balloon board IO voltages

What are the specifications for the I/O voltages on the Balloon board,
specifically on the SAMOSA connector?

Looking at the schematic, I see VDD_SAMOSA is sprinkled across J6 & J7
and that it is attached to VCC_IO through a switch. I suppose it's
possible that the supply is dynamically configurable from U5 (a
MAX_1586B). I'd have to go look at the data sheet, but I'm really
more concerned about the IO voltages on that connector. Are the 3.3V
or 1.8V?

For now, I'm going to assume 3.3V, but I hate that word ("assume").

--wpd