[aprssig] KISS mode definition request

[Stephen H. Smith]

CTDay at lbl.gov wrote:
>
> Could someone post a definition of KISS mode to the APRS Wiki, please? 
> I've seen lots of references to it but no definition anywhere. I don't 
> have any idea what is being talked about. Thanks.
>
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A conventional TNC is a combination of a radio-oriented modem and a 
command interpreter in firmware.  When packet radio was born in the late 
'70s/early '80s, most users were using dumb ASCII terminals (not 
computers).   The interpreter would process commands hand-typed from a 
keyboard to set the call sign, digipeater path, set monitor modes, 
beacon intervals, beacon message contents etc.     


The TNC would have two modes.  One was ("COMMAND") where what you typed 
was "swallowed" by the TNC hardware as a command.  The other was 
"CONVERSATIONAL" where what you typed was sent over the air instead.   
To get from the COMMAND mode to the CONVERSATIONAL mode you typed the 
command "CONV <ret>.  To get back from conversational mode back to 
command, you would typically type CNTRL-C.  The exact syntax of this set 
of commands varies from one manufacturer to another.  


Today, virtually all TNCs are used connected to a computer running 
specialized software instead of a dumb terminal.   The variety of 
different command formats is a constant headache to software writers 
that have to accommodate numerous different ways of saying the same 
things to different pieces of hardware.     Not to mention having to 
constantly toggle the TNC between the COMMAND mode and the CONV mode.   


The KISS (literally an acronym for "Keep It Simple Stupid") mode 
bypasses the human-oriented command interpreter inside the TNC, and uses 
the TNC strictly as a PAD (packet assembler/disassembler) and modem.  
Once commanded into the KISS mode, the assumption is that ANYTHING sent 
into the TNC is to be transmitted. Period.    The process of 
interpreting commands, or acting on incoming data from the RF side,  is 
handled entirely inside a program running on the PC.     Theoretically 
the KISS interface behaves identically on ALL hardware with the KISS 
capability. (Some very old TNCs don't support KISS.)   


The KISS mode can also bypass any digipeater functions that may be in 
the TNC hardware/firmware, and allow a much more sophisticated 
digipeater function to be implemented purely in software on the PC.   
This software-based digipeater will function in the same manner on any 
TNC with KISS capability.  This is unlike TNC-firmware-based digis where 
capabilities can vary wildly from one mfr to another, or from one 
firmware revision to another.


KISS mode also makes possible much simpler and cheaper KISS-only TNCs 
since they don't need the extensive firmware ROMs and processor 
"horsepower" to interpret human-typed commands.    However this kind of 
simplified modem-only TNC will ONLY work with a KISS-aware program or 
device.





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


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