Lightning Connector

From The Apple Wiki
Lightning connector compared to USB
Lightning connector from aerial, front, top, and socket angles

Lightning is the "new" connector supported by iPhone 5 and newer, iPad mini and newer, iPad (4th generation) and newer, up to but not including the 2018 iPad Pro line, (iPad Pro (11-inch) and iPad Pro (12.9-inch) (3rd generation)), and iPod touch (5th generation) and newer. Siri Remote and Apple Pencil also use Lightning. (For the old connector, see 30-pin Connector.) It was presented by Tim Cook at an Apple Special Event on 12 September 2012 (2012-09-12). According to Apple, it as an all-digital connector and "features an adaptive interface that uses only the signals that each accessory requires and also is 80% smaller as well as orientation independent."

  • Lightning is adaptive.
  • All 8 pins are used for signals, and all or most can be switched to be used for power.
  • The outer plug shell is used as ground reference and connected to the device shell.
  • At least one (probably at most two) of the pins is used for detecting what sort of plug is plugged in.
  • All plugs have to contain a controller/driver chip to implement the “adaptive” thing.
  • The device watches for a momentary short on all pins (by the leading edge of the plug) to detect plug insertion/removal.
  • The pins on the plug are deactivated until after the plug is fully inserted, when a wake-up signal on one of the pins cues the chip inside the plug. This avoids any shorting hazard while the plug isn’t inside the connector.
  • The controller/driver chip tells the device what type it is, and for cases like the Lightning-to-USB cable whether a charger (that sends power) or a device (that needs power) is on the other end.
  • The device can then switch the other pins between the SoC’s data lines or the power circuitry, as needed in each case.
  • Once everything is properly set up, the controller/driver chip gets digital signals from the SoC and converts them – via serial/parallel, ADC/DAC, differential drivers or whatever – to whatever is needed by the interface on the other end of the adapter or cable. It could even re-encode these signals to some other format to use fewer wires, gain noise-immunity or whatever, and re-decode them on the other end; it’s all flexible. It could even convert to optical.

Female Receptacle Pinout

The Lightning connector receptacle
Lightning connector mechanical drawing (front)
Pin Function
1 GND Ground
2 L0+ Lane 0 positive
3 L0- Lane 0 negative
4 ID0 Lane 0 ID/control
5 Vcc 5V power
6 L1- Lane 1 negative
7 L1+ Lane 1 positive
8 ID1 Lane 1 ID/control

Adapters

When a Lightning adapter is plugged in to the device it will connect to

http://mesu.apple.com/assets/com_apple_MobileAsset_MobileAccessoryUpdate_haywire/com_apple_MobileAsset_MobileAccessoryUpdate_haywire.xml

where, similar to an OTA iOS update, it looks for any new update bundles. This would only be for any in-between updates, though, since both iOS 6.0 and 6.1 come with predownloaded adapter firmware bundles located at /System/Library/PreinstalledAssets. (Each firmware bundle is about 11MB uncompressed.)

For fun, you can also monitor the device Console using Xcode or iPCU while connecting the adapter; you’ll see logs very similar to what happens during an iOS DFU restore, as the device loads firmware onto the Lightning adapter, as the boot chain starts off very much like a normal iOS device, but img3 files for iBSS are uploaded, along with an APTicket. This APTicket remains static for every digital AV adapter. The kernel is then uploaded and then booted.

Lightning to 30-pin Adapter

Lightning to 30-pin Adapter

This adapter lets you connect devices with a Lightning connector to many 30-pin accessories but some 30-pin accessories are not supported. The adapter supports analog audio output, USB audio, as well as syncing and charging. Video output not supported. The chips inside look unfamiliar and some have lasered text. They all appear to be custom and probably some are integrated audio circuitry in a larger processing chip. One of the chips reads Apple on it with a very long serial number. Another reads 8533 23AP CAB.

Lightning Digital AV Adapter

Lightning Digital AV Adapter

The Lightning Digital AV Adapter and Lightning VGA Adapter, codenamed Haywire, are accessories based on the Samsung S5L8747 that produce a 1080p HDMI or VGA video output by upscaling video received over the Lightning data bus.

External Resources