Is it possible to get the API details and protocol details from an MFI certified Accessory Manufacturer?
The Apple MFI NDA requires that accessory developers not divulge any information about the device protocols, security chip, interface, etc.
However, device manufacturers are allowed to create libraries and SDKs that others can use to release apps that use their device.
One example is Redpark, for instance I have a few of their serial cables:
http://www.redpark.com/c2db9.html
You have access to as much of the device as they permit through their SDK, and you can release apps using that SDK that works with their device. You can search the app store for "redpark" and find many apps that use their various iOS cables.
So yes, it is possible - nothing in the Apple NDA prevents them from disclosing and providing their API to others. They simply cannot disclose Apple's protocol/API/interface to others.
Do note that Apple requires a company to submit device samples and use cases for MFI approval, and it appears they don't allow many developers to develop devices for which they plan to release SDKs. There have been efforts to create universal infrared remote accessories for instance that haven't been opened even though the developers originally intended to provide an SDK. One I discussed this with indicated that Apple wouldn't approve their device unless it was tied to one, and only one app - theirs. I understand in cases such as redpark the developers made the cables for specific customers and specific apps first, then started making generic cables for generic apps after initial approval.
So there still may be some reluctance on the part of Apple to allow developers to design open API devices.
While your question is about MFi accesories, a number of third party accessories have come out which are not MFi. Many use Wifi or the audio jack to communicate with their iOS apps, such as http://www.60beat.com/ . Several credit card readers plug into the audio jack. Not all of them give their SDK/API freely, but you can always ask.
I would say unlikely.
- if a partner in the MFI program is creating a device that works using standard protocols and APIs then there would be no need to contact the manufacturer since the APIs are open
- if a partner in the MFI program has created a device with custom APIs and non-standard protocols then they will have created their own App to talk to their device and would have no reason to open their APIs
The exception are manufacturers who want to be the next big thing, creating devices that they want to be integrated into other apps. They will use proprietary protocols and APIs but open them up for outside developer use in the hope of gaining traction in the marketplace for their hardware and pehaps becoming a standard. In this way they move from being the latter to the former . Sometimes they will want you to licence their IP to develop your App in return for the information.
The only way to find out which is contact the manufacturer in question and ask them.