USB cable/socket questions.
Bobb Fwed
Posts: 1,119
What does a USB cable have in it 4 wires or 5? The USB-mini sockets I use have 5 connections, but only 4 are used. The Cable I use has 4 connections in the full-size USB plug. Maybe the 5th connection is connected to the shield or something? Please explain.
What I want to know is if I did a USB-mini to USB-mini connection could I use all 5 connections?
I guess I could cut open a USB cable, but I want to keep them all in tact. And maybe a mini-to-mini cable (which I don't posses) may be different than full-size to mini cable.
What I want to know is if I did a USB-mini to USB-mini connection could I use all 5 connections?
I guess I could cut open a USB cable, but I want to keep them all in tact. And maybe a mini-to-mini cable (which I don't posses) may be different than full-size to mini cable.
Comments
There's a wiring diagram here
http://www.maxim-ic.com/app-notes/index.mvp/id/1822
http://en.wikipedia.org/wiki/Usb#USB_Mini_and_Micro_connectors
From the wikipedia page above:
1 VCC Red +5 V
2 D− White Data −
3 D+ Green Data +
4 GND Black Ground
The couple of cables that I've cut up had the correct color wires. But, I wouldn't necessarily count on it without checking.
I actually wanted to use the 5th pin for connection detection (not quite what I want, but I may be able to use it).
So how exactly do I do host/device detection? Put an AB or B socket on my "slave" device. Then short the ID pin to GND on the A (or AB) socket on the "master" PCB? Once that is done, how do the devices detect which side is shorted or open (which is master and slave)?
USB In a simple term is done as a master slave system ..
( one day I was so bored I read the entire USB white paper .)
I encourage everyone to read it . its very interesting .
this lack of true Duplex BI data on 2.0 and below was one of the reasons Firewire ( ieee 1394 ) was/is "faster In real life " per generation .
the Unused Pin is sometimes used for charger detection for phones.
Be aware the GND and cable foil sheathing is not tied on both ends to the same point in some applications .( GND loop issue ) . the whitepaper will explain how to implement USB in a Good manner
-Phil
Always wondered why. So what are the limitations of firewire? Is it less flexible because it has rigid TX/RX lines? Can slave devices not swap rolls and become masters?
and it is . most will never need the Bandwith FW can do .
FW can have a max of 63 per bus .
In realty USB was meant to Kill the PS2 and RS-232 and thats it .
nothing more.
( funny how you can still find New PCs with PS2 10+ Y after USB)
FW was ment to replace LPT and SCSI .
In USB it is kinda possable to swap master slave but its not supported natively on 99.9 devices today. cause the master needs far more intelingece then the other devices . this is why a Ipad can go both ways as ita 1GHz A4 has the Horsepower to act as a USB master .
where as the little chip in my mouse is well, as dumb as a mouse .
the way USB protects this system is to have A to B plug system .
In nutshell here is what Wiki said
""USB was originally seen as a complement to FireWire (IEEE 1394), which was designed as a high-bandwidth serial bus which could efficiently interconnect peripherals such as hard disks, audio interfaces, and video equipment. USB originally operated at a far lower data rate and used much simpler hardware, and was suitable for small peripherals such as keyboards and mice.( like PS2 / RS-232)
The most significant technical differences between FireWire and USB include the following:
* USB networks use a tiered-star topology, while FireWire networks use a tree topology.
* USB 1.0, 1.1 and 2.0 use a "speak-when-spoken-to" protocol; peripherals cannot communicate with the host unless the host specifically requests communication. USB 3.0 is planned to allow for device-initiated communications towards the host (see USB 3.0 below). A FireWire device can communicate with any other node at any time, subject to network conditions.
* A USB network relies on a single host at the top of the tree to control the network. In a FireWire network, any capable node can control the network.
* USB runs with a 5 V power line, while Firewire in current implementations supplies 12 V and theoretically can supply up to 30 V.
* Standard USB hub ports can provide from the typical 500 mA[2.5 Watts] of current, only 100 mA from non-hub ports. USB 3.0 & USB On-The-Go supply 1800 mA[9.0W] (for dedicated battery charging, 1500 mA[7.5W] Full bandwidth or 900 mA[4.5W] High Bandwidth), while FireWire can in theory supply up to 60 watts of power, although 10 to 20 watts is more typical.
These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, FireWire 400 is faster than USB 2.0 Hi-Bandwidth in real-use,[55] especially in high-bandwidth use such as external hard-drives.[56][57][58][59] The newer FireWire 800 standard is twice as fast as FireWire 400 and faster than USB 2.0 Hi-Bandwidth both theoretically and practically.
***********************'
Sources...
from Wiki USB http://en.wikipedia.org/wiki/USB
And Wiki FW http://en.wikipedia.org/wiki/FireWire
Peter