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Originally Posted by zippyt
Now USB 1 v USB 2 , whats the deal ??
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USB 1.1 or USB 2.0. Latter is significantly faster which is why Firewire is now so much a niche product promoted by too few vendors (Apple, Sony, etc). Firewire's initial advantage was speed. USB 2.0 eliminated that advantage.
USB 2.0 uses diferent standards from USB 1.1. To get to USB 2.0, first, communication negotiates between device and port using USB 1.1 hardware. This means USB 2.0 ports and devices must support both USB 1.1 and 2.0 hardware - two completely separate functions inside a same chip. Even interface driver and receivers (the semiconductor that connect to USB cable copper wire) for USB 1.1 and 2.0 are different.
To you, any detachable USB cable for low, full, and high speed will be USB 2.0 standard with a type A and a type B connector at each end. Low speed only USB 1.1 cables will not have a standard USB connectors at one end. IOW a low speed USB will connect to a hub (type A) but will not have the USB standard 'B' type connector for device end. B type connector is the more square type connector. A type is the larger more rectangle type connector.
USB extension cords are prohibited. Maximum cable length is determined by mechanical paramters inside each cable. Maximum cable length is not defined by USB standards. Length is defined by the cable manufacturer whose cable must meet USB electrical signal parameters. If he can make a 50 foot cable to meet those parameters, then he can sell it as a USB cable. Don't expect to find 50 foot USB 2.0 cables which are typically 5 meters or less. USB extenders for up to 100 and 500 meters:
USB Extenders use ethernet or fiber optics
Whereas 'low speed' in USB 1.1 was up to 100 kilobits per second (analog modem speeds) and 'full speed' USB 1.1 was 12 kilobits per second (writing at diskette speed); 'high speed' USB 2.0 is 400 Mb/sec (faster than ethernet speed).
Whereas classic RS-232 software was trivial - I would write serial port code in assembly. USB 2.0 software is about as complex as MS-D0S due to the so many things that simple serial port does.