It seems that the HP iPAQ h6315 has the same pin pattern on the bottom as all the original iPAQs, including the 3800, 3900, 5400, and 5500 series. That being the case, I thought I could get fancy and plug it right on to my old Compaq iPAQ Foldable Keyboard.
Immediately I heard the same connection sound heard when connecting the included thumb keyboard, and I was off and running. Not only did it fit perfectly, but it didn’t even need to have any different drivers installed. The thumb keyboard’s drivers must be based on the same standard.
All of the hotkeys work, too. So if you have an old one of these keyboards laying around and are looking into the iPAQ h6315, you may want to hold on to it!