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[aprssig] Questions about paths

Scott Miller scott at opentrac.org
Tue Sep 7 20:42:49 UTC 2004


> Maybe Scott can put that feature in his up-and-coming project, if it
> has enough horsepower to do that sort of computation on the fly.
> Keep it to integer subsets of lat/long and it'd be easy to compute.
> It'd be harder to have to decode the Mic-E and Base-91 compressed
> packets before checking for a fit.  Should be easy for OpenTrac
> packets too I'd think.

Piece of cake.  For OpenTRAC packets especially, since for a rectangle it's
just doing a few integer comparisons.  I've been thinking about adding that
sort of comparison to the config change criteria for the OpenTracker, so you
could have it switch configs based on where it's at.  Memory's running a
little short for that, though.  Might have to wait for my next tracker
project... I'm aiming for 8 or 16 profiles in that one, to allow a sort of
primitive scripting.

An example for a high alititude balloon tracker might be something like
this:

Profile 1 - Startup and ascent
 path = relay, wide2-2
 switch to profile 2 when altitude > 10,000 feet

Profile 2 - At altitude
 path = <none>
 switch to profile 3 when time > 18:00 or outside area

Profile 3 - Cut-down
 Set output pin high (connected to cut-down device)
 switch to profile 4 when altitude < 10,000 feet

Profile 4 - Recovery
 path = relay, wide2-2
 switch to profile 5 when GPS lock lost

Profile 5 - Recovery (no GPS)
 CW ID only
 switch to profile 4 when GPS lock acquired

The ability to set an output pin based on the profile is something I'll
probably implement in the current OpenTracker, but there's really only one
available pin to do it with, and two profiles.  Switching based on GPS lock
lost/acquired (for x seconds) is on the to-do list, as is the area rectangle
test.  With plenty of profiles available, it'd probably make sense to have
the ability to test at least two separate sets of conditions to allow
branching rather than just a linear flow as demonstrated above.  CW ID has
been partially written, but won't fit into the standard firmware for the
existing hardware.  I'm planning a custom AX.25 + CW + PSK31 beacon for the
PropNet guys, though.

Scott
N1VG






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