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Page: of 39

saimhe

Lithuania
135 Posts

Posted - 14 mars 2006 :  21:06:07  Show Profile  Reply with Quote
quote:
Originally posted by Carl@SiRF

"-" is the first character in a Field if the value is nagative. When used, this increments the specified size of fixed length fields by one.

However the receiver gives "-3" instead of "-03" -- as per printf() format string "%02d". Therefore -10 would be reported as "-10", right?

This means that parsing is not so trivial, especially where every microcontroller instruction counts :|
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Carl@SiRF

USA
159 Posts

Posted - 14 mars 2006 :  23:14:02  Show Profile  Reply with Quote
Code space is not tight in the receiver, and I suspect we don't worry about holding to exactly 2 character spaces plus the sign. That type of thing is typically handled quite well by parsers, so is not an issue.

Carl - SiRF Customer Support
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saimhe

Lithuania
135 Posts

Posted - 17 mars 2006 :  03:05:24  Show Profile  Reply with Quote
quote:
Originally posted by Carl@SiRF

Code space is not tight in the receiver, and I suspect we don't worry about holding to exactly 2 character spaces

Actually, if "receiver" means "GSP2e/LP", you made an opposite point here. To conform to the specification, merely a different format string, "%03d" instead of "%02d", would be required for negative values; in a case of trivial approach, this costs additional five bytes and a couple of instructions. (I still assume printf() as C is the core language in the ARM ADS 1.2.) One must be REALLY tight in code space to sacrifice conformance here :)

Enterprise politics aside, it's interesting though how large these negative elevations may be. Simple geometry at the present altitude limit, 18 km, yields horizon angle of about -4°. OTOH the Binary Protocol Manual specifies the navigation mask in MID 139 down to -20°. I believe the first one is more realistic, right?

Edited by - saimhe on 17 mars 2006 03:06:51
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Carl@SiRF

USA
159 Posts

Posted - 17 mars 2006 :  17:04:55  Show Profile  Reply with Quote
Negative elevation angles generally only happen before the receiver has solved for its current location. Prior to that, when doing a warm start (or during some of the stages of a cold start), the receiver assumes a location and predicts visibility. If its position assumption is wrong, those satellites with negative elevation could in fact be above the horizon. That is why they are searched when there are channels available. Consider that you navigate in one location, then hop on an airplane and fly part way around the globe, then try your receiver again. Unless we widened the satellite search to include potentially unavailable satellites, we might find 1 or 2 satellites that both locations could see but no more. By looking for those we expect to be below the horizon, we dramatically improve TTFF in those situations.

Carl - SiRF Customer Support
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merrypig

44 Posts

Posted - 18 mars 2006 :  07:58:11  Show Profile  Reply with Quote
I'm using sirfdemo 3.81; with a haicom hi303iii. My problem isn't switching in and out of SIRF mode - this I can do and have it happily updating the maps/satellite info etc.

What I can't do however is get any feedback from 'poll' commands. Ie poll nav parameters, or software version. In my response view window it is spitting out time/clock drift messages continuously; in my output window I see all sorts of status messages.

but clicking poll\nav parms or poll\software version seems to do nothing.

Is this a common issue ? Am I missing something on how to get the readback of the settings? Even haicom told me to just do the poll menu option but I can't get anything like what is described in this thread or their email to happen.

Any ideas?
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NormGa

USA
13 Posts

Posted - 18 mars 2006 :  18:41:35  Show Profile  Reply with Quote
I am having the same problem with a HaiCom Hi-305 as merrypig.

But my question is about the DGPS view window on SIRFdemo 3.81. I lock into the WAAS satellite 122, get a 40 dB signal, and see a status of 3F. The mode shows 3d+Dgps. But when I look at DGPS view, all the satellite corrections are +276.80 m with an age of zero. The other parameters in this window are blank. This never changes.

What am I doing wrong?
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gpspassion

93884 Posts

Posted - 18 mars 2006 :  19:06:07  Show Profile  Visit gpspassion's Homepage  Reply with Quote
hum...how about taking a quick look around existing threads http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=51234 ?

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merrypig

44 Posts

Posted - 19 mars 2006 :  23:23:25  Show Profile  Reply with Quote
So, you're saying that sirfdemo is broken with sirfstarfIII chipsets?

And for the record, I did search all over google. Over half of the posts I came up with all referenced this one thread at various points. Since it was about sirfdemo and no other links had come up anywhere else, it didn't to me that there might have even been another thread.

My apologies, but thanks for the link too.

Anyone know of a similar tool that does work?
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gpspassion

93884 Posts

Posted - 20 mars 2006 :  13:34:33  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Sure, not a problem for the other thread, just feel free to use it now ;-)

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NormGa

USA
13 Posts

Posted - 24 mars 2006 :  23:54:58  Show Profile  Reply with Quote
I am beginning to believe that the Sirf III chip has a personality. Some days it is talkative and responds quickly. Other days it just sits there and ignores me and all my software toys. Can someone help me understand the moods of this precocious child?
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gpspassion

93884 Posts

Posted - 25 mars 2006 :  00:05:08  Show Profile  Visit gpspassion's Homepage  Reply with Quote
Well it's just a computer, you make it sound like it might be HAL ;-) Any specifics on the problems you are encountering ?

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admin_0

1 Posts

Posted - 01 avr. 2006 :  09:55:38  Show Profile  Reply with Quote
I have a BT-338 to which I'm trying to connect using SiRFDemo 3.81 on a desktop PC running Windows XP. My Bluetooth software tells me that it has created a serial port on COM6 for the device. When I try to connect to it in SiRFDemo at 38400 I get the dreaded "Cannot create UART handle. Comm port is not available or may be in use" error. All indications are that the port does indeed exist and no other applications are using the port. What have I fouled-up or forgotten to do? Thanx!
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markus.wagner

2 Posts

Posted - 12 avr. 2006 :  10:33:51  Show Profile  Reply with Quote
Hi!
I am wondering if everything is alright with my new GPS receiver. I bought a Haicom 303III CF(with Sirf III).

When just plugging it into the CF slot and following the NMEA output at 4800bps I can see, that a lot of NMEA sentences are sent.
But: Although being under best conditions, all satellites found are lined up vertically "in the middle" of the earth map.

So, i thought, lets try with SirfDemo - same output; except, that no satellites are shown in the radar window.

Switching the device to Sirf-Mode (either by command or sending raw $PSRF...) does nothing to the device. Using "WinFast Navigator" I had success to put the device into Sirf mode (what does it do different?). Now, if i keep power to the device and hook it to SirfDemo I can use it in SirfMode and see the found satellites. All lined up vertically in the radar window. When switching around with SN, all the sudden the sattelites start to move. But when unplugging or explicitly switching back to NMEA mode, I am at the beginning.

Now my question - is the device somewhat borker?! Case to send it back or is there a chance that I can do something about it?!

Any help is very much appreciated.

Markus

PS: I rather consult a forum where experts are; ordinary customer service here has never heard of NMEA and alike... (and I wish I wouln't have to know either)
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paulkbiba

USA
5064 Posts

Posted - 12 avr. 2006 :  14:58:57  Show Profile  Reply with Quote
It takes a while for a receiver to get its first lock on the satellites. See here: www.gpspassion.com/fr/articles.asp?id=157&page=3#ttff

From what you say it looks as if it is working OK and you just have to be sure it is outside with a clear view of the sky to let it get a lock.

As a newbie I wouldn't play around with SirfDemo. There is nothing it can do for you other than to get you even more confused. Forget about it.

Moderator
Don't forget the GPSPassion Club!
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markus.wagner

2 Posts

Posted - 13 avr. 2006 :  00:44:33  Show Profile  Reply with Quote
Hi!

I am aware, that it can take sometime to get a fix! Therefore I went to a nearby hill, open view to the skys in all directions, no clouds. There it took 1-2 minutes to get the first 2,3 satellites - after about 30 min it hat 9-11 satellites. This is still somewhat ok to me - but all satellites are in exactelly one line "under north N"?!?

And when switching modes, etc (see mail) all the sudden all those satelites move apart and I get a fix?! Still sounds weird to me - and if it takes more than 30min to get a fix under perfect conditions, then -sorry- sirfIII is nothing what is promised...

BTW - I have some experience with other GPS receivcers installed in gliders and other avionic, so I somewhat have an idea, how long a fix might take, even with bad receivers...

Thanks for the hints anyway!

Greetings,
Markus
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