Lightning is the "new" connector supported by iPhone 5 and newer, iPad mini 1G and newer, iPad 4 and newer, and iPod touch 5G. (For the old connector, see 30-pin Connector.) It was presented by Tim Cook at an Apple Special Event on September 12, 2012. 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.
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