Does anyone have detailed information about the lens protocol used in old Nikkor AF and AI-P lenses? I wonder if it should not be impossible to make custom chips by using a 1$ PIC12C508 or similar. Open source preferred. Why that? Nikon doesn't sell chips to everyone, and they are expensive. Chips from old lenses don't often fit the apertures of the manual lens to be upgraded. An MF lens with an AF chip makes the Camera try to AF, not so good. Even if you find a chip with suiting apertures, the focal length is different. Thats what I found out myself: The names of the lens contacts could be found in some old service manuals that can be download on the internet. Search for 'n90.pdf' with google. I recently dissassembled an old Nikkor 35-70/3.3-4.5 to see whats inside. The only important thing is a NEC uPD7554G577. The datasheet was hard to find, but I now have one, which I could mail to anyone who's interested. The NEC CPU is an old and slow 4-bit one, so the protocol can't be that complicated. I drew a sipmle schematic to show the connections. But I don't have a logic-analyzer to figure out what data is transmitted. Could anyone help?