Order Tray | Contact Us | Home | SIG Lists

[aprssig] KPC-3 <> AGWPE PROBLEM (Clarification)

Stephen H. Smith wa8lmf2 at aol.com
Mon Feb 28 23:04:00 UTC 2005

jfkraus3 at cox.net wrote:

> I am trying to get PE-Pro  running with a KPC-3 non plus version 6.
> With AGWPE this happens while trying to create a TNC port:
> I get a:  Can't open serial port error.  Probably you specified an 
> illegal port! etc.
> Same thing happens with KPC-2, KPC-4, KPC-2400.
> Yes I have tried deleting AGWPE.INI and PORT0.INI.
> Yes I made sure that no programs are holding the port open.  This 
> would likely cause problems to the other programs as well.
> Any suggestions?
What kind of serial cable are you using to connect the TNCs to the PC's 
serial port?   Is it only a three-wire hookup with RXD, TXD and 
GND/common only?   If it isn't a full cable with complete handshaking 
(i.e. at least 5 or 6 conductors carried through end-to-end) , some apps 
will work and some won't .

 [Some apps only look for the data lines TXD, RXD and GND/common, while 
others are very fussy about  RTS/CTS, DSR, DTR, etc being properly 
asserted. ]  

I found this out the hard way when programs I wrote in QuickBasic simply 
wouldn't work on ports/cables that worked fine with several commercial 
programs.  After struggling for nearly a week, I finally discovered that 
QBasic is very fussy about proper handshaking (unless you added a 
special argument to the OPEN PORT command) while the commercial pgms 
could care less about anything except TXD and RXD.   

If the cable doesn't have all the conductors (or the device at the far 
end doesn't assert the handshake lines correctly), you can almost always 
make a serial port hookup talk by  shorting these pins together in the 
DB9 female at the PC end of the cable:

Short pins 7 (RTS) and 8 (CTS) together
Short pins  1 (CD),  4 (DTR) and 6 (DSR) together

This pinout is for a standard 9-pin PC serial port.   On a classic 
25-pin port, the equivalents are:

Short pins 4 and 5 together.
Short pins 6, 8 and 20 together.

Stephen H. Smith             wa8lmf (at) aol.com
Home Page:                   http://wa8lmf.com

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

More information about the aprssig mailing list