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[aprssig] TNC-X anyone?

scott at opentrac.org scott at opentrac.org
Mon Aug 28 15:54:20 UTC 2006


> True, but it is a true KISS TNC.  It can handle packet lengths 1K in 
> length and it has a significant transmit buffer that allows it to 
> continue to take in outgoing data while it is waiting for a busy 
> frequency to clear up (note that KISS does not support flow 
> control, so 
> the data will keep coming!).  If the only thing you ever want 
> to do with 
> it is APRS, these things may not matter (or they might, if you are 
> digi-ing on a busy frequency).  For other applications they 
> certainly will.

John makes a good point - the T2 was designed from the ground up for APRS
and doesn't have a lot of buffer space.  The buffer could be expanded with
an optional FRAM, but the waveform synthesis takes a lot of CPU time and as
the firmware stands now it doesn't buffer incoming data while it's
transmitting.  You wouldn't want to use it for TCP/IP or bulk file
transfers.

On the other hand, the software-based modulator means it'll also transmit
PSK31 (and I'm working on RTTY), and the audio level can be set in software.
It was that flexibility - and the difference in cost - that kept me away
from the MX614 for this project.

Eventually I'll port all this to a chip with the horsepower to do real DSP,
but that's going to take some time.

Scott
N1VG







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