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Thread ID: 35827	2003-07-22 11:36:00	USB Cables	Poppa John (284)	Press F1

Post ID	Timestamp	Content	User
162106	2003-07-22 11:36:00	Curious . Why is a USB connection purportibly (spelling?) faster than, say, a 9 pin connector. It is not just the piece of wire surely?. More to do with what card it is plugged into? Yes? No? Poppa John	Poppa John (284)
162107	2003-07-22 11:54:00	Different technology and communication protocols PJ, that's the simple answer. Google will give you more info if you really want it. Cheers Billy 8-{)	Billy T (70)
162108	2003-07-23 01:38:00	In fact a 9 pin (serial) connector really only uses 3-4 wires. Serial: Pin 5 = Ground Pin 3 =Data + (xmit) Pin 2 = Data - (Recv) USB: Same as above but has a +5V pin (USB Power) OLD Serial (pretty much) used to have things like DTS/CTS and other sort of communication things (most of the other pins) to set send & recieve modes (1 way & then the other). All these old complexities were OK for their time because it was a way of error checking & to make sure that there were no communication problems. USB differrs as it doesn't need it, it is a faster bus also as it is more reliant on the PC to most of the 'thinking' - hence why USB printers are cheaper than Parallel printers. (Less brains). USB streams data faster as it doesn't need as much technical checking behind it and todays PC's are much more capapble of doing the communication. Hope this helps. Also although USB 1.1 is 12Mbps - it only equates to 1.5MegaBytes a second.. USB 2.0 is just a much harder pump for data on that cable. Hope this helps.	kiwistag (2875)
162109	2003-07-23 02:07:00	Not quite true . . . It's basically that the technology has changed . The highest rate for serial RS232 on PCs is 115200 because of the design of the original IBM PC in 1981 (and the original PC couldn't go more than 9600 because of the slow CPU and UARTs used) . Parallel printers were cheaper than RS232 ones for a long time . A USB one is cheaper now, because of the much cheaper connector . The interface electronics don't count, because its all in one complicated chi, which is "the printer chip" . :D RS232 as a communications standard is deliberately limited in speed/distance (by slew rates etc) for noise reasons . Current loop links can go much faster, for other reasons . A parallel link, as well as needing (and because of) more wires runs into problems with slew (signals on different wires arriving at different times) . This is the reason why disk drives are starting to appear with serial interfaces . But "proper" drivers (say LP11) and receivers (say LN03) allowed parallel printer cables 100 ft long with no problems . An article in this months Silicon Chip magazine features a serial link between two microcontroller (PICAXE --- look nice) units using wet string as the "wire" . USB does look nice . When all the various manufacturers of things which use it come to better agreement on what the standards mean, it will be wonderful . :D	Graham L (2)
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