NA Burning (but completely unimportant) tech Q's

[Let'sgoflying!]

I notice the sheath on my 30-pin ipad charger cable is separating so I can see, and count, the wires within.
There are only 4.
30 pins, 4 wires.
Hmmm.

 

[flyingron]

That's all there are in USB: Ground, +5, and two differential data wires.

Note there's all kinds of things on the 30 pin connector. In addition to data in and out there are the audio and vidio connections, different power voltages than just +5, and some redundant grounds.

Here's the 30 pin pinout: https://www.theiphonewiki.com/wiki/30-pin_Connector

 

[slacktide]

That should not surprise you much, as if you take a look at the other end of the cable, there are only 4 pins in a USB type "A" connector, and you only need the 4 wires for a USB connection.

The rest of the pins are used when you connect the ipad to a dock, or other adapter cable, and provides analog audio in/out, serial (RS232) data in/out, Video out, and FireWire in/out.

https://www.theiphonewiki.com/wiki/30-pin_Connector

Many years ago I made a custom cable to download my JPI engine monitor to my iPhone using the RS232 connection. Also had to jailbreak the phone and write some shell scripts. Worked but was really clunky so I just use a beater laptop that I keep in the hangar now.

(edit - damn, Ron beat me to the punch. Same link too!)

 

[Let'sgoflying!]

I am no electronics designer.
I am a simple country boy with a voltmeter.
When I see 4 wires, I am thinking I can make the following possible connections:

1. wire 1 to wire 2
2. 1 to 3
3. 1 to 4
4. 2 to 3
5. 2 to 4
6. 3 to 4
maybe pairs ie 1 and 2 connected to 3 but pairs means you lose the discrete options ie 1 to 3 and 2 to 3
maybe when you plug the 30-pin connector into an ipad, it connects things within the ipad itself....but why would they do it in such an inefficient manner?

Still not understanding, despite the link, why 30 pins.
What might help is a wiring diagram, with all 30 pins in use, while connected to whatever is downstream of the USB connection.

 

[slacktide]

Because you can plug other things into an ipad besides just a sync cable. You can plug in a video adapter cable that uses different pins than the sync cable. Or you can plug in an audio adapter that uses some different pins. Or you could use a FireWire sync cable instead of a USB sync cable, which uses different pins on the 30 pin connector.

 

[Let'sgoflying!]

Because you can plug other things into an ipad besides just a sync cable.

Ah, so many of the 30 pins would be unused on the terminus of my 4-wire cable. Thanks, Dan.

 

[slacktide]

Exactly. They got rid of all those legacy features in the newer iPhone / iPad connector, called "Llightning." Also, they added an encryption chip inside the cable so that only Apple licensed cords will work correctly with it.... seriously.