I have an iPod Touch, purchased ~2010. It uses a cable with a 30-pin connector on one end, and a USB plug on the other end. Last time I looked, a USB cable only had four wires in it, So what was the point of Apple going with the 30-pin plug?
The newer Lightning cable has 8 pins on it. Why is Apple, even now, not using a connector with just four pins? What am I missing?
Think back, way back, to the iPod classic days. You weren’t supposed to actually plug your iPod classic into a computer directly with a USB cable. No, you had an iPod Dock, and the Dock had a plug on the back that you would then plug into your computer. But the dock also had a line out, and later with the iPod video it had video outs. And they were pushing hard for this ecosystem where everything had iPod docks, rather than just simple 3.5mm audio cables like all the other MP3 players on the market used. The idea was that your iPod would be a stereo, so it needed all of the plugs and ports that you normally see on the back of a receiver. Except those are huge, so they condensed them down to a 30 pin connector and then relied on the Dock to convert those to normally used ports.
eta: The lightning connector has 8 pins because it’s reversible, each pin has a pair that runs to the same wire.
This is what the pinout of the 30-pin connector looks like:
It was a very successful system, and allowed a HUGE ecosystem of audio and video components powered by iPods and iPhones - something that no other competing device even approached.
For proprietariness, so you have to buy your connectors and all your other accessories from Apple or companies who have paid Apple a license. And with the technical points I make below, it was apparently pretty dead easy to make, say a speaker dock, resulting in a MASSIVE amount of “iPhone” speaker docks and other stuff out there, the volume and available of which no doubt encouraged people to buy iPhones (and then stay with them once they’d already invested in that ecosystem.
Technical: the dock connector does a lot of other stuff besides USB transfer. Yes, 4 of those 30 pins are for USB (ground, power, data+, and data-). There are also pins for Audio Input (L and R), Audio Output (L and R), Video (SVIDEO, Component Y, Pb, Pr), Firewire, Power/Ground, and other proprietary/special uses.
That connector was a sort of hybrid that could carry both digital and analog signals, making it simpler for docks/devices to provide certain features (analog audio output means you just have to amplify the signal on those pins, no decoding or conversion, etc.). The Lightning connector uses fewer pins, but is all-digital and the pins are “adaptive” – it’s up to the devices being connected to negotiate what’s going on and what pins are used for what. This is simpler for the user, but more complicated for the device maker (in having to add controller chips and drivers and whatnot). Still eight pins instead of four, because I believe the devices could simply negotiate something like “pins 5 and 7 will be Audio L and R” and then pass an analog signal through, as before, which even though the negotiation and control of that is digital, amplifying the analog signal is cheaper for the accessory than having to have built-in audio decoding or digital-to-analog converter chips.
The socket has eight pins on one side (and none on the other), but the plug on the end of the cable has eight pins on each side. The Wikipedia page gives a pinout for all eight of those contacts, but it’s not clear how all eight of those relate to the four pins of a USB connector.
Ah, my bad. :smack:
Well, the lightning plug has a little chip built into it for authentication. It could be that those extra data pins are to allow the device to communicate directly with that chip.
As noted the 30 pin connector carried a huge amount of stuff. They weren’t an Apple proprietary design - you could buy them off the shelf (I have a box of ten somewhere). All sorts of functionality was carried. It was never formally publicly documented, but was reverse engineered.
The Lightning connector isn’t actually USB. In their current implementation all devices are capable of talking USB-3 over the connector. But the spec allows for future use of other protocols. It is supposed to be pretty future proof. And of course reversible. Which is done with some careful assignment of pins and smarts in the device. The Lightning to 30pin adaptor is quite smart, and include an analogue to digital converter to allow the audio output pins in the 30-pin to work. It does not however include the video out capability.
The Iphone is happy to detect USB data on one of the pins ,and then revert to USB mode … it can assume it should send USB data on the appropriate pin…
If it hasn’t detected USB, its talking via its two “lanes” , in lightning mode.
It can also receive or send USB power on the power pin , too.
Interestingly the 30 pin connector could carry 1080p video with the AV adaptor while the lightning connector seemingly cannot.
The lightning-HDMI adaptor actually has a arm SOC embedded into the connector which is doing a conversion from compressed h264 to HDMI. Thats why this adaptor costs $50.
Also why it won’t to 1080p. The 30 pin connector was just wires, and the video the responsibility of the actual iDevice. The Lightning to HDMI adaptor is treated by the iDevice in the same manner as an Airplay device. There just isn’t the grunt in the SOC to do anything faster. Next revision perhaps. (Then we will complain it won’t do 4K.)
