[aprssig] Re: aprsd Mic-E Problem..was passcode

Curt, WE7U archer at eskimo.com
Thu Jun 22 07:16:08 CDT 2006

On Thu, 22 Jun 2006, Ron wrote:

> I've heard rumors of problems with Mic-E 'mangling'
> but have not seen any difinitive explanation.
> My Aprsd Server ver aprsd 2.1.5b9 has been running
> reliably for years and this is the first time I've
> heard it may have a problem. This version does not
> have AX25 and the tnc is in plain cmd mode.

There's a potential problem:  Command mode.  Many TNC's filter out
non-printable characters by default.  I think this is often the
MFILTER setting.  Mic-E uses 4 or 5 non-printable characters, I
think a few right below the space character, and one up near the top
of the set, something like 0x7e or 0x7f?

Anyway, TNC's in command-mode, if not set up to turn off this
filtering, will accept the packet off the air and then very
helpfully strip those characters off the packet before shipping the
packet up to your computer.

For some AEA TNC's: MFILTER 0
Paccomm PicoPacket: MFILTER 0
KAM:                FILT OFF
KPC3:               FILT OFF
TNC2:               MFILTER $00

I believe those are correct.

Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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