I opened up my RFGuys 5300 (non-Lightning) cable, it looks like there's an RS232-RS485 converter chip in the base. The connector is a Hirose RP13. I haven't put in the time to research the Lightning connector.
As for Lightning heads, I don't think there are a ton of them out there compared to the standard heads.
EDIT: Those are keyload cables for the SMA keyloader, which used DB9 conectors. NOT programming cables.
Holy! This is the most helpful thing I've heard yet! The connector is a key piece, so I've ordered 2 of the connectors and about 30 pins, just to be safe.
Any chance you have a part number on the keyloader, or pictures of it? I just ordered a usb a RS232-RS485 connector, that I can hopefully plug right in, but we will see.
Also, if there is any chance I could convince you to snap a few photos of the wiring on the converter chip, just the first time here and any pictures should go a long way.
Another interesting note, the 5300 service manual has the full URI schematic so if someone wanted to roll their own programming cable, that's all they would really need to know. USB to RS-485 adapters are also a thing now so I'm curious how a direct serial connection would function.
I literally just found the schematic this morning after trying a million service manuals (
link) and just like mentioned, page 8-85 (214 pdf) it was there. This appears to be the schematic for the first version of both the radio and the rpi, but it should work. I'm still digging for something from version 2, but idk if ill ever find it.
I'm gonna try a direct plug and play and see if it works, and if not, it looks like I've got enough there to make my own.