LinFBB / F6FBB over KISS

This is the recommended FBB setup for AXLoRaTNC.

Use AXLoRaTNC as a normal serial KISS TNC, attach it to the Linux AX.25 stack with kissattach, then let LinFBB use the kernel AX.25 port through interface 9 in port.sys.

WA8DED hostmode remains available for compatibility testing, but KISS is the preferred route for a stable BBS link over LoRa.

TNC setup

Configure every AXLoRaTNC node with the same radio settings:

mode console
callsign YOURCALL-0
radio reset
profile fast
mode kiss

For real RF operation, replace profile fast with legal duty-cycle settings. profile fast disables the duty guard and is intended for bench testing or a dummy load.

Linux AX.25 port

Create or edit /etc/ax25/axports:

# name    callsign    speed  paclen  window  description
axlora    YOURCALL-3  115200 64      1       AXLoRaTNC KISS

Attach the TNC:

sudo kissattach /dev/ttyACM0 axlora
sudo kissparms -p axlora -c 1 -f n -t 0 -s 10 -r 255

Use /dev/serial/by-id/... instead of /dev/ttyACM0 if you want the port name to survive reboots.

For more robust long-range LoRa settings:

sudo kissparms -p axlora -c 1 -f n -t 20 -s 10 -r 192

LinFBB port.sys

In LinFBB, use Linux interface 9 and point MultCh at the AX.25 port name from /etc/ax25/axports.

Minimal example:

# Ports TNCs
1      1

# Com Interface Address Baud
1      9         0      115200

# TNC NbCh Com MultCh Pacln Maxfr NbFwd MxBloc M/P-Fwd Mode  Freq
1     4    1   axlora   64    1     1     10     00/60   XUWY  LoRa

# TNC Nbs Callsign-SSID Mode
# 1   1   YOURCALL-1    B

A ready-to-edit example is included in the repository:

examples/linfbb-axloratnc-kiss-port.sys

Important values:

• Interface 9 means LinFBB uses Linux AX.25 sockets.
• MultCh axlora must match the name in /etc/ax25/axports.
• Pacln 64 keeps LoRa airtime short.
• Maxfr 1 is recommended for LoRa.
• NbFwd 1 keeps forwarding conservative until the link is proven stable.

Basic test

After starting LinFBB, verify the Linux AX.25 port exists:

ip link show axlora
axlisten -a

On the AXLoRaTNC console, useful diagnostics are:

console
radio
stats
mheard
mode kiss

If raw_rx rises on AXLoRaTNC but axlisten is quiet, check that the TNC is still in mode kiss and that kissattach is attached to the correct serial device.

If pieces of text are missing, check stats on both TNCs. qdrops must stay at zero. A rising qdrops counter means the KISS host is feeding frames faster than the LoRa side can transmit them. Lower Pacln to 40-64, keep Maxfr/window at 1, and make sure both TNCs were configured with profile fast or equivalent KISS parameters.