[time-nuts] M12+T more confusion

Chris Kuethe chris.kuethe at gmail.com
Fri Nov 21 23:29:03 UTC 2008


On Fri, Nov 21, 2008 at 3:06 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
> You are enabling output messages, right? Sounds like the
> order in which you individually *enable* one or more messages
> is unrelated to the order in which, once a second(*), all selected
> messages are *output*. I've never confirmed if they are output
> alphabetically or by size or priority or what. Does someone know
> for sure? Or does it matter?

i've not seen a gps yet that doesn't act like there's a big,
fixed-order list against which the enabled output messages are checked
once per reporting cycle. it's not impossible to dynamically schedule
a specific order of messages at a certain rate by building an array of
function calls, but that sounds like more work... the first way can be
done with a single char comparison per message.

some messages are certainly more expensive to generate (GSV vs GLL)
and are probably less interesting - so long has there is a good fix
and a navigation solution the average user probably won't care too
much about satellite locations. And the fix data will be more relevant
if you can output location immediately after it's calculated, rather
than delaying it 200ms for a satellite status report. Some receivers
do have certain message types triggered at set time - I hear SiRF's
ZDA message is supposed to be sync'd with the top of the second.


-- 
GDB has a 'break' feature; why doesn't it have 'fix' too?



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