GPIO Voltage limits?

What are the voltage limits on the X15’s GPIO pins?

3.3V, same as the BBB? Does it have the 1.8V in limit on any pins, like the BBB has on its ADC pins?

I’ve been pouring through the SRM & Quick Start Guide, and haven’t found this info yet. Not on the product webpage, either. Shouldn’t info needed to not fry your board be prominent?

3.3V on GPIO pins…

There are no ADC pins.

HDMI is 1.8V but those are specific outputs.

SATA is differential.

PCI is 1.5V differential