The iPhone can use the Lightning to USB adapter with iOS 9.2
As of iOS 9.2, any compatible iPhone can now connect to the previously iPad-only Lightning to USB adapter. Not only does this bring photo import to the iPhone via USB cable (or by using Apple's old or new Lightning to SD card adapter, but it also offers quick recording on the go for musicians, too.
By default, Apple's Lightning to USB connector is marketed as a camera connection tool: Plug your camera into a USB cable, plug the cable into the adapter, plug the adapter into your iOS device of choice, and you get a photo import menu.
But early on, music enthusiasts discovered that the USB cable could also provide an unsupported connection for low-powered MIDI instruments and microphones—and, with the addition of a powered USB hub, a connection for pretty much any USB-oriented music tool.
The iPhone unofficially offered this support even before iOS 9.2, but now the USB adapter is officially supported as a camera tool—which makes the music support, we suppose, "officially" unofficial.
It's likely that the bulk of the adapter's use will still remain on the iPad—it makes a lot more sense to plug your MIDI keyboard and play onto a screen you can easily see and rearrange—but connecting an adapter to the iPhone makes it more feasible for musicians who want to record something on the road or outside their normal studio to do so.
There's still the power problem, of course: The USB adapter has a software limitation in place that supports just 20mA, which renders most USB-powered devices unable to connect. (Amusingly, even my made-for-iPhone Shure MV51 doesn't receive enough power through the adapter, though it can be powered directly through the iPhone with a direct USB to Lightning cable.)
As such, if you want to use most MIDI or audio equipment, you're still going to need some sort of powered hub in your kit. Given my recent iOS audio gripes, I'm hoping we might see a reimagining of the USB adapter like Tuesday's SD Card revamp that provides more power and official support for these devices. (And maybe even other USB-powered items. Webcams? Hard drives? A girl can dream.)
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Regardless, I'm still pretty excited to see both music and camera support on the iPhone—even with caveats, the USB adapter can be a great tool for musicians and photographers alike.
Updated at 1:30PM ET to correct information about the iPhone's previous support of the USB adapter. Thanks, Marco!
Serenity was formerly the Managing Editor at iMore, and now works for Apple. She's been talking, writing about, and tinkering with Apple products since she was old enough to double-click. In her spare time, she sketches, sings, and in her secret superhero life, plays roller derby. Follow her on Twitter @settern.