<div dir="ltr">The computer industry found itself in a spot with multiple interfaces for multiple things.<div>MoBos were MUCH easier to build if you could cut down on the number of different types of interfaces.</div><div>The original mouse port was a db9 serial.</div><div><br></div><div>The original serial interface was designed for terminals and modems.</div><div>The RS-232 standard actually has TWO data channels in it, the second being a much slower interface.</div><div>This secong channel was designed for controling the modem and the dialer.</div><div>The "ATDT" command set allowed "in band signalling" and this removed the need for the second data channel.</div><div>The "Xon-Xoff" protocol removed the need for hardware handshaking.</div><div>The DB25 which was about 3in wide shrunk to the DB-9 that was only 3/4in wide.</div><div><br></div><div>What we got from USB, was the ability to use the same protocol for keyboard, mouse, serial, external drives, and in some cases audio & video.</div><div><br></div><div>USB serial ? How does that differ from RS-232?</div><div>USB serial is "TTL level" which means the signal is either 0 or +5 and thats it.</div><div>RS232 is interesting. It was designed to tolerate long cable lengths.</div><div>Ones were between -5 and -25, zeros were between +5 & +25. Voltages between -5 & +5 were invalid as weere voltages in excess of 25 or either + or -.</div><div>Default USB serial is 115k baud.</div><div><br></div><div>By moving to USB, you could also plug any usb device into any usb socket as the bus queries the device and figures out whats what.</div><div>Its all about making computers easier to use so that even morons could use one.</div><div><br></div><div>Technology has marched so far along that even the dimwitted YOTUS (Twitterer Of The USA) is able to use one!</div><div><br></div><div><br></div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 18, 2019 at 11:21 AM Michael Paoli <<a href="mailto:Michael.Paoli@cal.berkeley.edu">Michael.Paoli@cal.berkeley.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">DE-9 (or DE-09), *NOT* DB-9 (nor DB9 nor DB-09). Many folks get this<br>
wrong ... sometimes even vendors' documentation is incorrect.<br>
A DB-9 (were there such an animal) would have the same shell size as<br>
a DB-25, but with only 9 pins.<br>
Once upon a time, Electronics, Etc. in Berkeley had an excellent<br>
display of the various connectors ... and their proper labeling.<br>
<br>
See also: <a href="https://en.wikipedia.org/wiki/D-subminiature" rel="noreferrer" target="_blank">https://en.wikipedia.org/wiki/D-subminiature</a><br>
<br>
> From: "<a href="mailto:paulz@ieee.org" target="_blank">paulz@ieee.org</a>" <<a href="mailto:paulz@ieee.org" target="_blank">paulz@ieee.org</a>><br>
> Subject: Re: [conspire] conspire list hacked?<br>
> Date: Mon, 18 Feb 2019 18:32:00 +0000 (UTC)<br>
<br>
> Regarding USB cables. Before USB there were serial ports. In those <br>
> days, we all had a variety of devices with the DB-9 connector. <br>
> Using a new connector with an older device was a challenge. Several <br>
> companies offered adapter cables. The ones by FTDI actually worked <br>
> well. On the outside they looked like a simple cable with USB A <br>
> connector on one end and DB9 on the other. Molded into the cable <br>
> was a custom chip that provided an active interface. More than <br>
> once, I had to explain to someone that they couldn't just use an <br>
> Ohmmeter to figure out the pin connections. <br>
<br>
<br>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><br>R "Texx" Woodworth<br>Sysadmin, E-Postmaster, IT Molewhacker<br>"Face down, 9 edge 1st, roadkill on the information superdata highway..."<br></div>