how to connect to DSLR camera by OTG cable on iPhone

Question

I have tried to use EAAccessoryManager with swift:

let eaManager = EAAccessoryManager.shared()
let devices = eaManager.connectedAccessories

but the devices list is always empty, I searched this problem for two days on Google, but did not get any useful infomation, the Canon official remote control app connect to camera by BLE or Wifi, while the iPhone's photos app can access the DSLR camera and import photos from it by OTG cable. so I think there must be a way to implement solve it.

Answer 1

I found even if I connect to DSLR camera by OTG cable, user can't use the camera while connecting, because iPhone doesn't support PTP protocol, the connection is established by mount the camera's SD card, camera lose the sdcard once iPhone mounted it.
so the only way to connect to DSLR camera on iPhone is BLE or Wifi.