Re: [gpsd-dev] SiRF IV on gpsmon

[Eric S. Raymond]

Gary E. Miller <address@hidden>:
> I read the SiRF IV doc.  It specifically says that once you initialize
> a SiRCC IV that you must wait for each ACK before proceeding.  I found
> that by lengthening the delays between initialization messages that
> things work a bit better.  But the doc says that waits up to 4 seconds
> may be required annd that sending another message before the ACK will
> result in problems.  Looks pretty much like what I amm seeing.

OK, looking at code...I see your workaround. Has the problem that the
settle-down waits you put in potentially block message traffic from
the device, especially during the big sequence of configuration sends
at activation time.

There's a slightly better way to do it, I think.  The model is the way that
driver probes are spaced out over the first nine seconds of NMEA activation
- look in drivers.c:nmea_event_hook(). We can pull a similar trick in the
SiRF configure_event hook to space the 9 sends it wants to do over the
first 36 seconds, guaranteeing a 4-second interval between them.

Then we put a guard in sirf_write() itself that stalls until 4 seconds
have elapsed since the *last* send, then sends and updates the last-send
timestamp.  That way control sends will never fail or screw up the
device unless SiRF is being optimistic about the settling time.

Working on it...

> > Sorry, that was my error.  Those commands are disabled in client-mode
> > gpsmon.  It is theoretically possible they could be, but I'm not
> > going to try this before 3.10.  I've added an item about this to the
> > TO-DO.
> 
> It at least needs a warning message.

Each of the unavailable commands already generates one if you try it 
in client mode.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>

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