In packet radio, AX.25 is a fairly common layer-2 protocol. Many TNCs implement AX.25 in firmware, so the operator interfaces to the TNC with a serial port, using the TNC's firmware from a shell-like interface.

Many TNCs also allow a "raw mode" where data packets are sent directly over the serial port for the host computer to manage. KISS is a common protocol for this.

XKISS is "extended KISS" and it has about 3 very simple improvements over KISS. Kantronics TNC documentation indicates that it was conceived by John Wiseman, G8BPQ. Kantronics TNCs provide an XKISS mode, in addition to a standard KISS mode.

TAPR has some detailed documents for AX.25 and KISS on their FTP site. Where is some documentation to describe XKISS in detail?

  • $\begingroup$ and what is XKISS? $\endgroup$
    – Dan KD2EE
    Commented Oct 30, 2013 at 23:42
  • $\begingroup$ Thanks for the additional information, hopefully someone has the answer $\endgroup$
    – Dan KD2EE
    Commented Oct 31, 2013 at 0:14
  • $\begingroup$ XKISS is the name Kantronics uses for the BPQKISS multi-drop extension to KISS created by John Wiseman, G8BPQ. The fundamental differences between BPQKISS and standard KISS is that BPQKISS may include checksumming in the framing between the computer and the TNC and that BPQKISS may include an address byte to allow several TNCs to share a single serial port connection to a computer. Documentation, as suggested by the original post, is not readily apparent online, but may be available from the BPQ32 Yahoo group, where G8BPQ is an active participant. $\endgroup$
    – James NF8I
    Commented Oct 31, 2013 at 1:30
  • 1
    $\begingroup$ I've just gotten an email from the creator, John Wiseman, G8BPQ, who tells me that he doesn't have any specification document available at this time, but he does have source code, which he says he will use to make some notes available. $\endgroup$
    – James NF8I
    Commented Nov 1, 2013 at 1:48

1 Answer 1


Karl Medcalf, WK5M, of Kantronics, has published a paper titled Multi-Drop KISS operation for ARRL CNC v10 conference (San Jose, California, 1991). That document was distributed as a PostScript file, at some point a copy was in the source code of the Linux ax25-tools, in the doc directory. It seemed a bit hard to find an URL for the file now, so I ran it through ps2pdf and placed a copy on my server:


I checked the old G8BPQ DOS software installers, which include the BPQKISS firmware, hoping to find an original spec. KISSROMS.DOC says:

The protocol used for this multidropped option was changed from version 3.59a onwards to be compatible with similar software produced by KANTRONICS for their range of TNCs. The new version is called BPQKISS, and replaces the old JKISSP.

I would expect Karl's document to document XKISS as implemented by Kantronics. This recent post (2010) by John Wiseman, G8BPQ seems to say so:

The Kantronics XKISS uses the same enhancements as my BPQKISS.

The Linux kernel AX.25 implementation (mkiss module) is apparently based on that document, so that's one place to look into if you wish to see actual source code.


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