Apple’s Lightning USB


 

Debuting alongside the iPhone 5 — just ahead of the fifth-generation iPod touch and seventh-generation iPod nanoApple’s new Lightning to USB Cable ($19) replaces the classic 30-pin Dock Connector with a considerably smaller design.

While a recent analysis of Apple’s Lightning USB cable shows that the pins on the plug aren’t arranged symmetrically, suggesting that the Lightning port can dynamically reassign signals to each pin on the fly. “Dynamic assignment of the pins is the only way for the USB data to be routed” over the cable, according to boutique cable maker Double Helix Cables.

While the standard USB power is routed symmetrically, so that it always aligns with the same pin on the Lightning connector, the data pins are not.

“Take top pin 2 for example,” Double Helix’s Peter Bradstock told AppleInsider. “It is contiguous, electrically, with bottom pin 2. So, as the plug is inserted into the iPhone, if you have the cable in one way, pin 2 would go into the left side of the jack, flip it the other way and the same pair of pins is going to match up with the other side of the jack (as the electrical contacts in the iPhone’s jacks are along the bottom).”

Apart from that, the Lightning connector is very similar in size to a Micro-USB plug, and quite a bit smaller than the older Mini-USB connector

As Apple noted during the iPhone 5 introduction, the Lightning port was designed as a purely digital interface that could adapt to various output needs now and in the future. So the dynamic pin assignment design makes sense—it’s the only way Lightning could work with USB 2.0, HDMI, VGA, or even possibly USB 3.0—though it does seem somewhat overkill for the needs of USB 2.0. Perhaps the varied pin routing discovered by Double Helix lets the iPhone 5 recognize the type of cable plugged in.

 

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