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[aprssig] Re: Serial port to USB question

Andrew Rich vk4tec at tech-software.net
Sun Sep 4 02:25:07 UTC 2005


it is because your usb to serial adaptor gets confused about handshaking to
the radio

i get it all the time


  -----Original Message-----
  From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Stephen H. Smith
  Sent: Sunday, 4 September 2005 12:20 PM
  To: TAPR APRS Mailing List; victorf at windreader.com
  Subject: [aprssig] Re: Serial port to USB question


  victorf at windreader.com wrote:
    I am attempting to connect my D700 to APRSPoint. I have a 'modern' Dell
laptop sans serial ports. I can attach the TNC output to a USB port using a
Belkin Serial => USB converter and can see the APRS packets streaming into a
terminal program - 9600Baud, 8N1. So I am sure the converter is working and
the comport selection matches what is found in the Windows XP Device table
(com4 in this case). However attaching in EXACTLY the same way to APRSPoint
and setting the TNC port as above does not work. I get the error message
"TNC not detected". I have MapPoint 2004 installed and am using AP 2.1 for
MP 2004. I AM a registered user of both MP and AP.
  Serial-to-USB converter "dongles" vary wildly in how faithfully they
emulate a real serial port.  Especially how they emulate (or don't emulate!)
the hand-shaking lines of a real serial port since these lines don't exist
in USB. Some will work only with some programs, others with nearly all.
The Belkin converters are especially notorious for poor compatibility and
have been repeatedly blasted on this list,  the UIview mailing list and the
MixW list.

  Some of the variables involved are:
  o     What IC chipset is the cable based on?
  o     What IC chipset is used for the USB ports on the PC?
  o     Are the PC's ports USB 1.1 or 2.0?
  o     Are you going directly into a PC's USB "root port" or through a USB
hub or splitter?
  o     What operating system (Win 98SE, Win2K or WinXP) are you using?
  o     What patch or service pack level is your OS at?
  o     How many other USB devices are in use at the same time?
  o     Does the application depend on accurate handshaking or does it only
require the basic RXD/TXD/Gnd three-wire serial hookup?  [This often drives
sound-card-interface users to despair since the serial port's handshaking
lines are used for Radio PTT, CW keying, Receiver squelch detect, etc. ]

  The Edgeport converters have frequently been commended as being among the
most trouble free on the UIview list.   I have personally used SIIG and
pFranc/Purple Computing cables with my D700 and TH-D7.

  The Purple Computing (actually MCT Technology) cable works successfully to
connect my D700 to UIview, APRSplus and APRSpoint, or to feed a GPS into
Delorme Street Atlas or Precision Mapping 6.0  or 7.0.  However it
ABSOLUTELY WON'T WORK to feed a GPS directly into MapPoint 2002 or 2004.
(The Microsoft web site even confirms that MapPoint will only work with
"real" serial ports!).

  [Note that I am referrring here to feeding a GPS directly into MapPoint
for a moving map display of my own location; not using an APRS application.
I am only citing it here to illustrate how inconsistent the behavior of
these devices are, and to illustrate  that "because it worked with app A but
doesn't work with B" doesn't prove there is anything wrong with your
etup.  ]

  The SIIG dual serial-to-USB works perfectly on everything I threw at it on
a PC with only USB 1.1 ports, but only works on another similar machine with
USB 2.0 ports with only about 2/3rds of the programs/hardware tested.

  A no-name generic cable with a DB9 encapsulated in transparent "Imac blue"
plastic that is based on the FTDI chipset, has worked flawlessly for 12
months 24/7 nonstop connecting a KPC3+ TNC to my APRN / HF-VHF-APRS /
Echolink "Ham Superserver" based on a Via EPIA-TC motherboard.

  On a 1.6 GHz P4 Centrino laptop (i.e. recent machine about 9 months old
with native USB 2.0 ports) running Windows 2K, a USB-interfaced Holux GPS
mouse will not work with MapPoint directly (It will with Streets & Trips!) ,
but WILL work if I have Franson GPS Gate (a utility that intercepts data
from a GPS on a single serial port and shares it with several programs at
the same time) in between the virtual serial port and the application.
       [The Holux, like all "USB" GPS devices, is actually a serial device
with a built-in serial-to-USB converter chip. These converters are identical
to the ones used in stand-alone serial-to-USB converter cables.  In fact the
Holux uses the identical chip and driver as the pFranc/Purple Computing
cable.  Thus the same random compatibiliy issues prevail. ]

  Bottom line:

  You will have to experiment with several different USB-to-serial dongles
to find one that works with your particular hardware and OS revision.

  Note further that the chronic random instability of Windows
"Plug-and-Pray" auto-configuration will cause some of these converters to
assign themselves a different virtual COM port number on successive boots.
Some of the better drivers for Win2K and XP give you an option, in the
Windows Device Manager, to assign and lock down the COM port assignment.




  Stephen H. Smith    wa8lmf (at) aol.com
  EchoLink Node:      14400    [Think bottom of the 2M band]
  Home Page:          http://wa8lmf.com

  "APRS 101"  Explanation of APRS Path Selection & Digipeating
    http://webs.lanset.com/wa8lmf/DigiPaths

  Updated APRS Symbol Chart
    http://webs.lanset.com/wa8lmf/miscinfo/APRS_Symbol_Chart.pdf

  New/Updated "Rev G" APRS     http://webs.lanset.com/wa8lmf/aprs
  Symbols Set for UI-View,
  UIpoint and APRSplus:












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