[Xastir] Linux AX25 KISS driver for Kenwood D700 (fwd)

[Curt, WE7U]

FYI.  I'll forward my response to this message next, as soon as I
get it back from the list.  This subject is certainly worthy of
discussing here as well.  The Winlink people have figured out how to
make TM-D710's reliable in KISS mode for their purposes.  If we
could do the same, without corrupting things too badly for other
devices, we should.  --we7u

---------- Forwarded message ----------
Date: Thu, 17 Dec 2009 14:34:47 -0800
From: Bill V WA7NWP <wa7nwp at gmail.com>
To: linux-hams <linux-hams at vger.kernel.org>
Subject: Linux AX25 KISS driver for Kenwood D700

Is this where the maintainers of the Linux KISS code would be found?
  A simple tweak would eliminate the possibility of some ASCI sequences
kicking the Kenwood D7 or D700 radios out of KISS mode...

We really need to feed this info back to Kenwood so they correctly fix
the D710.   I don't hold any hope in firmware updates for the D7/D700
so it seems tweaking the KISS generator is the best answer.

73
Bill - WA7NWP


---
The 710 “bug” is not a violation of the KISS protocol…it is the result
of trying to use the same serial port for both a TNC and a Front panel
control. The problem is when in KISS mode (which sends binary packets
“encapsulated in the KISS protocol”  it is possible to have the
character sequence “TC 0<Cr>”  as binary or  character data within the
KISS encapsulation. This sequence will be interpreted by the serial
port controller in the Control head of the D710 as “escape to control
mode” and which will switch the serial interface from TNC mode to
front panel control mode.  This can have disastrous affects when
trying to transfer binary files using KISS.



One solution would be to entice Kenwood to modify the firmware in the
control head to having entered the KISS protocol to ignore all mode
control commands including “TC 0<Cr>”. This would require using the
standardized escape KISS sequence {0xC0, 0xFF, 0xC0} prior to any
control panel commands and then re enabling KISS to continue TNC
operation…This gets tricky and is very likely to impact existing
programs that now work.



The solution we used and which appears to work well and is solid is to
escape the “C” character.  So when any data is sent to the TNC in KISS
mode if there is an ASCII “C” it is replaced by the sequence <0xDB>”C”
which essentially escapes the “TC 0<Cr>” sequence. The KISS protocol
(in the D710’s KISS TNC implementation) removes the <0xDB> which is
the frame escape so no modification of the transmitted data stream is
actually made. Thanks to Peter Woods for figuring this out.



73,



Rick Muething, KN6KB

Winlink Development Team
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