The pin functions are the same.*
However, it will work with your camera, but only as a simple trigger. The Xpro-P TTL supports P-TTL, but not Pentax TTL cameras that use off-the-film metering such as your 645NII.
Steve
*
Added: What I mean is that the shoe contacts are used for the same tasks as with other devices that use the 5P shoe. Per the diagram below the contact usage is:
- Digital: bidirectional communication between flash and camera using several serial data protocols.
- Trigger: provides standard X-sync
- Mode: provides legacy analogue protocol indicating flash mode; also used by analogue protocol TTL to send quench signal to flash
- Ready: provides legacy flash ready indication, but is widely supported by most bodies and devices.
Modern devices can support full functionality through the digital contact alone, but will honor the other three contacts as step-down support on older cameras.
Linked from the KMP site with full discussion
HERE