Apple's Lightning port dynamically assigns pins to allow for reversible use
A cabling expert has taken a closer look at how Apple's new Lightning connector works, and has come to the conclusion that the 8 pins on each side of the plug are dynamically assigned, likely thanks to the use of a unique chip in the iPhone 5.
Peter from Double Helix Cables first shared with AppleInsider last week his discovery that Apple's new Lightning connector cables feature integrated authentication chips. He has since taken an even closer look at Lightning and concluded that the layout of the pins must be dynamically assigned based on how the cable is physically plugged in to a device like the iPhone 5.
When it unveiled Lightning earlier this month, Apple noted that the new, all-digital connector "features an adaptive interface that uses only the signals that each accessory requires." But Peter's testing has shown that Apple's cable goes even further to allow for reversible use in either orientation.
Some features of the Lightning cable, such as USB power connections, are symmetrical on each side of the plug. That means that if the pins on Lightning are numbered from one to eight on each side, pin one on the top row connects with pin eight on the bottom row.
This allows users to flip the connector and plug Lightning into an iPhone 5 in either orientation. With this design decision, the lower right pin always makes contact with the same spot in the corresponding Lightning jack on the iPhone.
However, while the USB power connection is symmetrical, Peter's testing found that the data connections in Lightning are actually asymmetrical. As such, he believes that dynamic Lightning pin assignment is performed by a chip included on the iPhone 5.
"Take top pin 2 for example," he wrote in an e-mail to 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)."
Peter believes that the iPhone 5 Lightning port probably reads the type of data being sent from one of the pins, and then dynamically adjusts based on the orientation that the cable has been inserted.
"Dynamic assignment of the pins is the only way for the USB data to be routed, since I've proven that top pin 2 and bottom pin 2 are the pins that go to the Data+ connection of the USB," he said.
Dynamic pin assignment performed by the iPhone 5 could also help explain the inclusion of authentication chips within Lighting cables. The chip is located between the V+ contact of the USB and the power pin of the Lightning plug.
Given the apparent complexity of the new Lightning plug, Apple has seen a shortage of Lightning cables following the launch of the iPhone 5. This week, analyst Ming-Chi Kuo of KGI informed AppleInsider that the shortage has been caused by a change in supplier weighting, as well as low yield rates of the new cables.
The new Lightning cable and accompanying port are about 80 percent smaller than the legacy 30-pin dock connector. As a result, manufacturing Lightning cables has proven to be complex and has decreased the yield rate.
The inclusion of an authentication chip in Apple's Lightning cables means consumers are advised to steer clear of cheap third-party cables that have appeared for sale online out of the Far East. According to Peter, there is "basically no way those are functional cables."
Peter from Double Helix Cables first shared with AppleInsider last week his discovery that Apple's new Lightning connector cables feature integrated authentication chips. He has since taken an even closer look at Lightning and concluded that the layout of the pins must be dynamically assigned based on how the cable is physically plugged in to a device like the iPhone 5.
When it unveiled Lightning earlier this month, Apple noted that the new, all-digital connector "features an adaptive interface that uses only the signals that each accessory requires." But Peter's testing has shown that Apple's cable goes even further to allow for reversible use in either orientation.
Some features of the Lightning cable, such as USB power connections, are symmetrical on each side of the plug. That means that if the pins on Lightning are numbered from one to eight on each side, pin one on the top row connects with pin eight on the bottom row.
This allows users to flip the connector and plug Lightning into an iPhone 5 in either orientation. With this design decision, the lower right pin always makes contact with the same spot in the corresponding Lightning jack on the iPhone.
However, while the USB power connection is symmetrical, Peter's testing found that the data connections in Lightning are actually asymmetrical. As such, he believes that dynamic Lightning pin assignment is performed by a chip included on the iPhone 5.
"Take top pin 2 for example," he wrote in an e-mail to 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)."
Peter believes that the iPhone 5 Lightning port probably reads the type of data being sent from one of the pins, and then dynamically adjusts based on the orientation that the cable has been inserted.
"Dynamic assignment of the pins is the only way for the USB data to be routed, since I've proven that top pin 2 and bottom pin 2 are the pins that go to the Data+ connection of the USB," he said.
Dynamic pin assignment performed by the iPhone 5 could also help explain the inclusion of authentication chips within Lighting cables. The chip is located between the V+ contact of the USB and the power pin of the Lightning plug.
Given the apparent complexity of the new Lightning plug, Apple has seen a shortage of Lightning cables following the launch of the iPhone 5. This week, analyst Ming-Chi Kuo of KGI informed AppleInsider that the shortage has been caused by a change in supplier weighting, as well as low yield rates of the new cables.
The new Lightning cable and accompanying port are about 80 percent smaller than the legacy 30-pin dock connector. As a result, manufacturing Lightning cables has proven to be complex and has decreased the yield rate.
The inclusion of an authentication chip in Apple's Lightning cables means consumers are advised to steer clear of cheap third-party cables that have appeared for sale online out of the Far East. According to Peter, there is "basically no way those are functional cables."
Comments
Quote:
Originally Posted by Lerxt
Does this mean the chip is not required if a cable is produced that is not reversible?
Not really. Because the lack of the cheap would most probably never activate the Lightning port in any USB mode ("normal" or "reverted").
That would make a "Simple" (cheap) charging cable easier to make
One possibility: when the "authentication/control" chip signals the Lightning connector that a USB cable is present, BOTH connector 2 and 7 could be assigned to the D+ and 3 and 6 assigned to D- in the Lightning port on the iPhone.
That way, depending it on which way you insert your plug, pins 2 and 3 in the cable would connect with either the plug 2/3 or 7/6 pairs.
Quote:
Originally Posted by smiffy31
That would make a "Simple" (cheap) charging cable easier to make
If the iPhone expects a chip to be present to activate any mode, this would fail.
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Quote:
Originally Posted by Avonord
I had this argument with my friend before. You see -- Most of us only need 1 data cable. The rest of the cables are purely for charging the phone. As long as those third party cables can charge the phone properly, then it serves their purpose for most of us.
Exactly. I will only have to get one expensive chipped cable and a bunch for charging only (home, work, car, laptop bag, travel bag). Works for me.
But it raises the micro USB question again. If the cable's chip dynamically assigns the pins and can revert to a simple pin out when no corresponding chip is present, then why not terminate it in the micro USB used by 95% of portable electronic devices today. Everything without the chip could still charge the phone AND any accessory with the chip could take advantage of all the dynamic pin assignments. That way the world would need one fewer charging cable. The apologist will say Apple needs the extra pin (nonsense) or some other excuse. I think the real reason is Apple's arrogance.
I hope the phone PHY for the Lightning cable is robust.
Sure it's clever to switch the connections based on the way it's inserted but Apple could just make a 'mirrored connector' instead (same pin connections on each side).
It looks like it is just a way for Apple to prevent 3rd parties making cables, instead they have to sign up to Apple's licensing & manufacture to Apple's specs.
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All those numbers confuse me... so I think I'll use a random combination of them on my EuroMillions lottery ticket tonight!
I do wonder pins 2 and 7 (the power pins) are used for the association. You alter the impedance slightly or have the chip communicate over one or the other pin and the device's chip's will be able to know instantly which pins are for which orientation of the plug.
I feel as if the charging and syncing is faster with the new connector. I look forward to AnandTech's thorough review which should reveal this is it exists.
Because Lightening can act as dumb as Micro-USB is no argument that Lightening should have scraped, all its features be removed, and a far inferior connector be used.
I don't understand why you et al. purposely ignore the mandate on the EPS ruling. You know damn well it has nothing to do with the cabling but with the EPS. You also know damn well that Apple has been in compliance for 8 years with their EPS having a USB-A connector so that any vendor can use their EPS. Don't pretend you aren't aware of this.
Quote:
Originally Posted by UrbanVoyeur
Exactly. I will only have to get one expensive chipped cable and a bunch for charging only (home, work, car, laptop bag, travel bag). Works for me.
But it raises the micro USB question again. If the cable's chip dynamically assigns the pins and can revert to a simple pin out when no corresponding chip is present, then why not terminate it in the micro USB used by 95% of portable electronic devices today. Everything without the chip could still charge the phone AND any accessory with the chip could take advantage of all the dynamic pin assignments. That way the world would need one fewer charging cable. The apologist will say Apple needs the extra pin (nonsense) or some other excuse. I think the real reason is Apple's arrogance.
Micro USB connectors cannot carry the 2 amp current used to charge the iPad, it would take longer to charge. Try connecting an iPad or iPhone to a low power USB port (e.g. a Mac keyboard) and see how well that works.
Apple seem to want 'one connector' to do everything, from the iPod Nano up to the iPad. The tiny pins on Micro USB were not designed to take the higher current of the iPad. Those tiny pins are also fragile, sadly the standards bodies picked the crappy option to promote as 'the standard'.
You can buy a Micro USB to Lightening adapter if you want to test the iPad charging theory, I suspect the adapter has the authentication chips within it.
I think your theory that cheap cables will just work for charging is misguided. Apple put these chips in to sense if cables are up to spec. I doubt they will allow charging from cables that don't do the required negotiation first. I hope I am wrong.
And how does data work regardless of how plug it in if the device isn't dynamically routing the data?
Because USB ports are only allowed to be used as USB ports. You may recall Intel running into this problem when they wanted to use the USB port for Lightpeak (Thunderbolt).
I believe if Apple chose to use a Micro USB port, they would be restricted to protocols and configurations that are part of the Micro USB standard.
Quote:
Originally Posted by Droid
Can someone explain how consumers benefit from authentication chips within cables?
Sure it's clever to switch the connections based on the way it's inserted but Apple could just make a 'mirrored connector' instead (same pin connections on each side).
It looks like it is just a way for Apple to prevent 3rd parties making cables, instead they have to sign up to Apple's licensing & manufacture to Apple's specs.
It really depends on what you call "authentication chips".
If the purpose of a "chips within cables" is purely to enforce DRMs and ensure manufacturers pays a fees to Apple then indeed everybody loses except Apple shareholders (until demand lowers because of such pratices).
However, if the "chip within cable" has a purpose, as in the Thunderbolt cables or here to be able to specify which kind of cable this is and hence which pin mapping the iPhone 5 should use, then the user slightly loses because cables are more expensive (even without paying any Apple fee - or tax) because those cables are more complex to manufacture, but the user also gains from a sturdy, durable, compact and versatile connector that allows high energy current and various usage pattern a plain old cable would not allow.
Quote:
Originally Posted by SolipsismX
Nailed it! I forget who was saying I was stupid for thinking Apple would use adaptive pins for this new connector. I doubt they'll speak up now.
Actually, if you were to look back over the comments, you'll note that I continually maintained that the cable would be chipped to support higher speeds and updates to protocols. (True.) I said that the plug was data only. (True.) I also said one approach to making the connector reversible was mirroring the pin-outs, which, apparently, they did for the power line, if not for the entire plug. Speaking of reversible...
Quote:
Originally Posted by SolipsismX
Because they're Apple and yet no non-cylindrical data connector of theirs has ever been reversible?
'Nuff said.
Quote:
Originally Posted by SolipsismX
So lets consider your 8 pin design and then consider that USB 3.0 used 9 pins. Then lets consider the other pins that video out and audio line-out need, not to mention the other pins Apple has used and still uses in their dock connector for the accessories they have. Tell me how killing off the accessories market is your idea of thinking.
First, you'll also note that video out and audio line out are NOT part of the specification. Lightning is all-digital. (True.) The 30-pin adaptor and the Lightning to HDMI adaptor both contain chips and digital-analog converters in the ADAPTORS, not in the phone. Hence, your assertion that signaling in the cable would cause "sophisticated" circuitry in the phone to switch the lines to audio or video line outs is flat out wrong.
And you'll also note that Apple is, in fact, "killing off" the existing accessory market. Existing devices will use the adaptor or get tossed. Newer devices will use the new connector, or, as I also maintained, switch to Bluetooth and/or AirPlay. (True.)
So... what did you nail, exactly? (grin)
One other thing I've not really seen mentioned, is that the Lightning port can also function as a USB host, not just as a client. This -- with the proper adaptor -- would allow cameras and other peripherals to be connected to an iPhone or iPad.