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Old November 24th 03, 12:14 AM
Odd Erling N. Eriksen
 
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Default On address fields in AX.25 packets

Hi,

I am currently implementing a TNC following the specs in the v2.2 AX.25
protocol. Platform: An ATmega32 microcontroller. Will be a neat, little
package when I'm done.

Anyway, as I am rather tired now and the AX.25 paper appears to have
no other answer than "impossible" to my problem, I have a question
for this forum:

What if I wish to put a seven character callsign in the address field?
True, seven octets are reserved for each callsign, but one of these is
for the SSID. Can it be done?

What happens if I extend the source address field to eight octets?

Dependent on the TNC at the receiving end?

Will the last character simply be discarded?

Will the frame get rejected as not correctly formatted?

This problem is not hypothetical. The target application is a picosatellite
which has been assigned (Tentatively, at least) a seven-character call.

Perhaps I'd better spend my time talking the post- and telecom authority
into giving us a six-letter call, rather than trying to work my way
around a protocol limitation... :-)

--
73 de LB1LF

Odd Erling, ARK

"Das Lied schläft in der Maschine" -Einstürzende Neubauten