Author Topic: problem: my Venus GPS not getting fix  (Read 10782 times)

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Offline AdminTopic starter

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Re: problem: my Venus GPS not getting fix
« Reply #60 on: June 24, 2010, 04:08:04 PM »
Here are my quantitative results for the uBlox . . .

I took it outside and its fairly sunny out.

I got 8 sat locks. About 4 locks in under a minute (I didn't actually track elapsed time, but it was fast).

RMS was about 3.5 meters. Maximum deviation from center was 10 meters.

That occasional 10m jump outside of the RMS is disconcerting . . .

Offline madsci1016

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Re: problem: my Venus GPS not getting fix
« Reply #61 on: June 24, 2010, 04:23:00 PM »
If you are going to test it on your person or holding it, you try changing one of the navigational settings from "vehicle" to "pedestrian". It's something about what kind of motion the GPS expects to see.

Are you getting any WAAS signals? I usually see 2 where I live.

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Re: problem: my Venus GPS not getting fix
« Reply #62 on: June 24, 2010, 04:46:26 PM »
If you are going to test it on your person or holding it, you try changing one of the navigational settings from "vehicle" to "pedestrian". It's something about what kind of motion the GPS expects to see.
I just laid it down on a table . . .

Quote
Are you getting any WAAS signals? I usually see 2 where I live.
Where do I find that option? Wasn't really paying attention to the details . . . might be awhile before I run another GPS test . . .

Offline madsci1016

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Re: problem: my Venus GPS not getting fix
« Reply #63 on: June 24, 2010, 10:36:27 PM »
My laptop I had U-Center installed on died a while back, so I will have to install it again and find where those options are. I just remember hearing about the pedestrian vs vehicle modes on DIYdrones.

Offline madsci1016

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Re: problem: my Venus GPS not getting fix
« Reply #64 on: June 25, 2010, 12:50:35 PM »
Did you see that SFE just did an 'objective' GPS comparison test, yet the Venus wasn't tested. Convenient.

The Ublox did well though.

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Re: problem: my Venus GPS not getting fix
« Reply #65 on: June 25, 2010, 01:37:32 PM »
Did you see that SFE just did an 'objective' GPS comparison test, yet the Venus wasn't tested. Convenient.

The Ublox did well though.

Someone should have done that test ages ago!
http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=169

The ublox actually didn't do so well, they said it had a 'hiccup'. When I did my test yesterday, it also had a really bad similar hiccup.

This is of course just one single test, and they really should do multiple runs to get a definitive answer . . . and they used a different antenna type for each GPS unit, making it a poorly designed experiment . . .

but it looks like the Copernicus was the best unit . . .

Offline madsci1016

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Re: problem: my Venus GPS not getting fix
« Reply #66 on: June 25, 2010, 02:20:10 PM »
The ublox actually didn't do so well, they said it had a 'hiccup'. When I did my test yesterday, it also had a really bad similar hiccup.


Umm, what?

O I see, I was not 100% accurate, they tested the the 406, not the 407 (what our Ublox is). The 406 did well.
Quote
EM-406A Pros

    * Tried-Tested-and-True
    * Fix indicator LED
    * Excellent tracking data in all conditions
    * PCB is completely shielded
    * Plenty of online support

EM-406A Cons

    * 5V operation


Some other GPS that looks like ours was the one that had the hiccup, not ours.

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Re: problem: my Venus GPS not getting fix
« Reply #67 on: June 25, 2010, 02:32:17 PM »
The ublox actually didn't do so well, they said it had a 'hiccup'. When I did my test yesterday, it also had a really bad similar hiccup.


Umm, what?

O I see, I was not 100% accurate, they tested the the 406, not the 407 (what our Ublox is). The 406 did well.
Quote
EM-406A Pros

    * Tried-Tested-and-True
    * Fix indicator LED
    * Excellent tracking data in all conditions
    * PCB is completely shielded
    * Plenty of online support

EM-406A Cons

    * 5V operation


Some other GPS that looks like ours was the one that had the hiccup, not ours.


Looking closer, oops, yea it just looks like the ublox but isn't. That said, we have the GS407 (2nd image), not EM-406A (first image). The ublox wasn't actually tested, either.


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Re: problem: my Venus GPS not getting fix
« Reply #68 on: October 29, 2010, 04:48:40 PM »
This isn't even funny any more :(

I finally got around to trying out the Copernicus GPS by sparkfun:
http://www.sparkfun.com/commerce/product_info.php?products_id=8146
with this antenna (which shouldn't matter here):
http://www.sparkfun.com/commerce/product_info.php?products_id=177

I hooked up 3.3V to VCC, ground to ground.

I hooked up an oscilloscope to ground, and to both Tx-A and Tx-B (I tried both).

I kept it on outside for 20 minutes . . . it's cold out there!

Guess what happens? Nothing. No TLL signal. Tx-A gives a constant 1.8V, and Tx-B gives a constant 0V.


So I start reading the manual in detail, and see this on page 25:
"If you are using the serial port option, the XSTANDBY pin should always be held high."
So I apply 3.3V to this pin, but no change.

page 13 says:
"XRESET Active low logic level reset. Connect to VCC with or without a pullup resistor, if not used."
I apply 3.3V, no change.

Anyone manage to get this to work?

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Re: problem: my Venus GPS not getting fix
« Reply #69 on: March 09, 2011, 06:18:14 PM »
An update on the Venus GPS. (in conclusion, it still sucks)

I tried this antenna just to make sure I wasn't using the wrong one:
http://www.sparkfun.com/products/177

It couldn't get more than 2 sats fixed for the first hour. After about an hour, it suddenly jumped to 7 sat fix. It then gave me an RMS of about 30m over the next half hour.

I ran my uBlox GPS literally right next to it. The uBlox got a 3 sat fix in like 15 minutes, also with 30m RMS.
« Last Edit: March 09, 2011, 06:43:56 PM by Admin »

Offline madsci1016

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Re: problem: my Venus GPS not getting fix
« Reply #70 on: March 10, 2011, 07:51:26 AM »
I get the same with the Venus but...

my uBlox is solid. good sat fixes in my apartment and accuracy down to 2-3 meters. Enough to have my robot drive through a crowded parking lot and not hit anything.

Maybe you live in the bermuda triangle of GPS?

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Re: problem: my Venus GPS not getting fix
« Reply #71 on: March 10, 2011, 08:44:24 AM »
my uBlox is solid. good sat fixes in my apartment and accuracy down to 2-3 meters. Enough to have my robot drive through a crowded parking lot and not hit anything.

Maybe you live in the bermuda triangle of GPS?
Forgot to mention . . . I was testing it inside my apartment last night, near windows. I'm sure I'd get better RMS if I was outside. But it's cold and rainy lately . . .

I'm going to retry the Copernicus tomorrow, I think I figured out what was wrong with it.

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Re: problem: my Venus GPS not getting fix
« Reply #72 on: May 06, 2011, 11:37:33 AM »
I started a new thread to debug the Copernicus and uBlox here:

http://www.societyofrobots.com/robotforum/index.php?topic=13739.0

 


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