2012-09-23

The iPhone dock connector was bad, and Lightning is awesome

Numerous people in the press are mourning the loss of the iPhone's 30-pin dock connector.  A separate vocal group has often complained about the lack of a Micro-USB connector port on the iPhone.

Both these groups are complaining about Apple's new Lightning dock connector.

But at the end of the day, the Lightning connector is a great move for Apple customers.  Here's why

Limitations of the Micro-USB standard

The 2007 MicroUSB-B connector became a European standard for cell phones in 2010.   Although USB is a good standard, it is far from adequate for modern smartphone use in terms of power, data, or flexibility.

In terms of data, the 2000-vintage USB2 standard provides a practical maximum data rate of roughly 35 MB/second.  However, most smartphones need to deliver faster I/O.  HDMI, for example, requires a consistent 500 MB/second data stream with very low latency rate.  USB2 to HDMI conversion is therefore impossible without a loss in quality.

In terms of power, the USB2 standard stipulates a maximum of 500 milliamps per device, unless its a device on a bus used to charge devices.  But most modern smartphones require much more than 500 milliamps for charging, and so that means either fast charging OR data, not both simultaneously.

In terms of flexibility, USB as implemented on smartphones is as an endpoint device  - not as the USB bus master.  And therefore, the smartphone cannot control other devices on the bus.  The smartphone has as much control of the USB bus as a mouse has on your computer's USB bus.

What about USB 3.0?  Forget it. First of all, it still isn't fast or latency free enough to driver modern HMDI without loss of quality.   Secondly, the MicroUSB 3.0 connector is large and unwieldy, and therefore is not seen on smartphones.

Failings of the classic 30-Pin Dock connector

The dock connector has numerous advantages over the MicroUSB standard.  First of all, it isn't limited to USB - it can carry analog audio and video, as well as HDMI, VGA, and a host of other signals.  It's 30 pins gives it a ton a flexibility you just can't get with a 5-pin USB2 interface.

Secondly, the 30-pin dock connector is expert at zero-insersion force.  What this means is that one can build a standard cradle or dock, and the 30-pin connector can slide home with near-zero crankiness, and be removed with near-zero stick-to-it-ness.  If desirable, cables can add a catch/release mechanism to add connector security, if so desired.

But the dock connector's advantages have led to some disadvantages.  The connector's pins have changed substantially over the years, so few devices are actually universal - old chargers don't work with new docks, new cables don't fit old cases, yesterday's video cables don't work with today's devices.  In all, it has become a hodgepodge, a solution that covers a lot of ground, but which is far from universally compatible.


Which one is a new, official Apple product? [A: both]
Which one works with your iPod? [A: maybe the left one]
Which one fits your case? [A: maybe none]

The next time you're in a hotel, try your old iPod or your newer iPhone in that clock radio with a dock. Does it work as you'd like?  If so, congratulations - your device is of the same vintage as the hotel's clock radio.  Evolution is a bitch.

Glories of Lightning

Lightning introduces a standard very high-speed bus for the iOS platform, much like Thunderbolt for the Intel platform.  It uses active cabling to eliminate all the old-school signaling, and replaces it with a single high-speed bus that can be converted into anything that peripheral manufacturers want to produce.

Lightning is all digital, and so media conversions have to happen within active cables.  This makes it possible to add unlimited new features over time without adding or redefining the interface.  It's bus master is exclusively the iPhone, so the iPhone can control a host of devices (unlike the USB2-B standard crowd).

Lightning is not USB, and therefore isn't subject to USB's limitations.  An active cable along with OS software is used to convert Lightning signaling to USB signaling.

Lightning is as fast as the CPUs on the iPhone, so the practical speed limit is simply what's attached to the other end of the connector, not the connector itself.  HDMI's multi-gigabit speeds?  No problem.  Analog audio/video?  Easy.  USB3?  Absolutely possible.  And as the technology beat moves on, Lighting will be able to deliver.

But wait, how, with only 8 pins, can it be faster than USB3?  Easy.  USB3 is a specific bus arbitration communication standard that travels for meters.  In contrast, Lightning is a direct I/O bus for very short hauls.  What something else?  Make it true with the right converter chip built into the cable. Ethernet. SCSI.  RS-232.  Even 1-wire is within the realm of reason.



2 comments:

Jeremiah said...

"HDMI, for example, requires a consistent 500 MB/second data stream with very low latency rate. "

Should be 500Mbit/s, or?


And u should REALLY consider get rid of the captcha below, 11th try?

LanceJ said...

Nope, not 500 Megabit. The classic HDMI interface throughput rate is 4 Gbit/second. Modern HDMI is 8 Gbit/second. Divide by 8 to convert to bytes (or 10 if you're lazy).


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