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[aprssig] USB, Underwear, Washing Machines, and Serial Ports

Kent Hufford khufford at comcast.net
Wed May 28 22:25:42 UTC 2008

When I got into "computers" in the early 1980's, someone said to "Never buy
a computer from a store that sells underwear or washing machines." Don't
remember who that was. The idea at the time was to not buy a "PC junior"
from SEARS big box store. 


For some time, I had the impression that PC's, especially laptops cannot be
purchased with SERIAL ports anymore, just has USB ports. With the help of
some of the APRS forums, I found out that Toshiba, Dell, and HP do sell
laptops with real serial ports. still. Nice ones to great ones.


However, I went looking at Best Buy, Circuit City, Staples, even Micro
Center. None of them sold any of the three brands with serial ports. (Two of
the four stores sell washing machines <g>)


I could find them on the internet, mostly direct from them. Not the consumer
level that Best Buy sells, but "business/tech class". 


Yea, in the end, all of us will be USB.  Right now, many of us are SERIAL
people stuck in a USB world.  


The best things in life might be a GPS that has a serial port and a USB port
and a new laptop with serial ports.


I do like  my new D710. 






 Below, from Steve Smith, is a VERY good overview as to why you cannot just
connect a USB device to a serial port wanting device, that is not a


"As has been pointed out repeatedly on numerous APRS-related lists, USB  GPS
devices are *unusable* with standalone non-PC hardware like TNCs, TinyTraks,
Kenwood APRS radios, etc. 

There is no simple way to convert USB to serial. USB is a protocol  with a
master/slave relationship (normally referred to as host & client) in the
hardware. USB devices always require a full-blown computer or  equivalent on
the master end running a complex multi-level stack of  software to assign
USB devices an identity and to communicate with  them. You cannot connect a
non-computer USB "slave" device directly to  another non-computer slave
device. There must always be a computer "master" in the loop. You cannot
just wire two differently-shaped  connectors together. 

You would have to insert the equivalent of a small PC(or at least  something
with the computing "horsepower" of a PDA or smart phone; i.e.  many times
the capability of the Ti nyTrak or GPS CPU) typically running  Windows or
Linux between the GPS and a TT to do this conversion. 

Note that the common USB<-->serial converter cables a.k.a. "dongles" are
always plugged into a COMPUTER host or master; not another non-computer
device like a GPS, printer, modem, etc. 

Further, note the nature of USB cables. The wide, flat so-called "A"
connector always plugs into the computer host or master. The smaller  square
plug with beveled edges (a.k.a. "B" connector) always faces the  client or
slave device. The two different shaped plugs (rather than just male/female
versions of the same plug) are purposely intended to prevent users from
connecting two slaves or two masters directly to each  other.


Stephen H. Smith wa8lmf (at) aol.com"

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