[aprssig] TNC-200 Assistance

Stephen H. Smith wa8lmf2 at aol.com
Mon Jan 1 02:57:54 CST 2007

vk5jfk at activ8.net.au wrote:
> Should the DataBits be 8 and not 7
> Ben Lindner

Yes.    7-E-1 is an obsolete hangover from the mid 1970s when packet was 
born.  At that time, before personal computers, the dumb terminals and 
Teletype machines widely used with minicomputers (and also with and 
early TNCs) almost universally used 7 bits even parity.   This was 
before personal computing and binary files with 8-bit bytes.  [Mass 
storage was something you did with punched paper tape with 7 holes 
across the width of the tape.]  Somehow this configuration persists to 
this day as the default setting in TNCs.    For operation on APRS, you 
want 8-bit transparency.   For most TNC2 devices and similar, the TNC 
init file needs to issue the commands

    8BIT OFF   (meaning don't mask incoming 8-bit bytes off to 7 bits)

    AWLEN  8   (meaning use 8-bit long full bytes)

I have modified the final release of the official TAPR firmware (Ver 
1.1.9) to power up in 8-N-1 instead of the original 7-E-1 mode which 
makes it much more convenient for modern computer applications.    A 
binary file of this modified firmware, which can be used to program an 
EPROM, is on my website at:

     < http://wa8lmf.net/miscinfo/index.htm >  

On this download page of miscellaneous files and reference sheets, look 
for the file


As a added bonus, this release of the TNC2 firmware includes KISS mode, 
and alsd the first (and last) explicit support for APRS in the form of a 
dumb APRS tracker mode.  From an attached terminal, you command the TNC 
into the tracker mode, disconnect the terminal and then connect a 
NMEA-format GPS to the serial port.  The TNC will then transmit raw NMEA 
strings over the air in a manner similar to the dumb tracker mode on a 

Just above this item in my MISCINFO list  is a quick hack I threw 
together years ago in compiled Quickbasic (i.e. standalone .EXE) to send 
the command sequence to get a TNC out of KISS mode.  Look for


Rich Schiller wrote:
> Don;t know if this helps or not, but the serial number for the TNC is 
> 27446.  There are also labels, handwritten, on some of the e-proms, 
> they are as follows:
> State 1.09
> TheNet 2.11 st

TheNet is a replacement EPROM for the standard TNC2-style firmware, to 
use the TNC as a dedicated packet (not APRS!) digipeater.  The TNC is 
never going to function as a normal end-user unit with this firmware in 
it.    Remove this EPROM, erase it and reprogram it with the firmware I 
describe above. 

tim_cunningham at mindspring.com wrote:
> Rich,
> You must replace the TheNet EPROM with a TAPR  EPROM, a Paccomm EPROM, 
> or a KISS (JKISS) EPROM. The Paccomm EPROM v5.0 is still available 
> from Pac-Comm at http://paccomm.com/
> The KISS EPROM would work best if you plan to use the TNC with any of 
> the APRS software programs.

KISS mode will work with UI-View, APRSplus and Xastir.      It WON'T 
work with the original DOSaprs, APRSpoint or WinAPRS.  (None of these 
programs support KISS-mode operation.)


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

NEW!   TNC Test CD

JavAPRS Filter Port 14580 Guide

"APRS 101"  Explanation of APRS Path Selection & Digipeating

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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/aprssig/attachments/20070101/f808686e/attachment.html>

More information about the aprssig mailing list