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Re: [gpsd-dev] SiRF IV on gpsmon
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] SiRF IV on gpsmon |
Date: |
Mon, 18 Nov 2013 10:58:36 -0800 |
Yo Eric!
On Mon, 18 Nov 2013 04:21:06 -0500
"Eric S. Raymond" <address@hidden> wrote:
> 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.
I did not put those in, they were there, just not consistent. All I
did was make them consistent.
And yes, the sirf driver code has basically allowed no output from the
GPS while doing a large nnumber of control writes.
> 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.
The problem is, and I have tested this, if you always wait 4 seconds
then the GPS output buffer overflows.
> 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.
But the doc says to wait for the ACK.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
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- Re: [gpsd-dev] SiRF IV on gpsmon, (continued)
- Re: [gpsd-dev] SiRF IV on gpsmon, Gary E. Miller, 2013/11/13
- Re: [gpsd-dev] SiRF IV on gpsmon, Eric S. Raymond, 2013/11/13
- Re: [gpsd-dev] SiRF IV on gpsmon, Gary E. Miller, 2013/11/13
- Re: [gpsd-dev] SiRF IV on gpsmon, Eric S. Raymond, 2013/11/13
- Re: [gpsd-dev] SiRF IV on gpsmon, Gary E. Miller, 2013/11/14
- Re: [gpsd-dev] SiRF IV on gpsmon, Eric S. Raymond, 2013/11/17
- Re: [gpsd-dev] SiRF IV on gpsmon, Beat Bolli, 2013/11/17
- Re: [gpsd-dev] SiRF IV on gpsmon, Eric S. Raymond, 2013/11/17
- Re: [gpsd-dev] SiRF IV on gpsmon, Gary E. Miller, 2013/11/18
- Re: [gpsd-dev] SiRF IV on gpsmon, Eric S. Raymond, 2013/11/18
- Re: [gpsd-dev] SiRF IV on gpsmon,
Gary E. Miller <=
- Re: [gpsd-dev] SiRF IV on gpsmon, Sanjeev Gupta, 2013/11/15
- Re: [gpsd-dev] SiRF IV on gpsmon, Sanjeev Gupta, 2013/11/17