I've been waiting for more updates to the user documentation as well. Actually got feedback from Apple granting the vendor ID we're looking to use, but still no luck in getting a basic init/free extension working.

Okay, just to bring anyone viewing this up to speed. I've been trying a few different directions for this and most avenues seem to be dead ends, or at least in my case. One test that has partially worked is to take the IOKit and headers from the iPhone private framework and add that to the project. Which I know won't pass muster if sending to the AppStore. This is just for my own testing at this point. I create a notification port with IONotificationPortCreate and IONotificationPortSetDispatchQueue I can set a matching service using IOServiceMatching with the vendor and product IDs which I can retrieve from the Mac, and a callback routine with IOServiceMatchingCallback. When incorporated into an app and run, connecting and disconnecting the SparkFun Serial Basic Breakout board, with invoke the callback function with details of the device. This is a small step in at least the board is now being recognised when connected and removed from the iPad Pro. Sending or receiving data to or from the board is the next step. Any help in this regard would be very helpful. The SparkFun Serial Basic Breakout board allows the Tx and Rx to be connected together allowing a sort of echo function. This works when connected to an Apple Mac, this I'm looking to as the next small step. If anyone know a better solution please let me know.