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Electronics => Electronics => Topic started by: Admin on September 28, 2009, 10:26:14 AM

Title: problem: my Venus GPS not getting fix
Post by: Admin on September 28, 2009, 10:26:14 AM
I'm using this Venus GPS:
http://www.sparkfun.com/commerce/product_info.php?products_id=9133 (http://www.sparkfun.com/commerce/product_info.php?products_id=9133)

All I'm getting from it is:
Quote
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$GPRMC,120554.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*7B
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPGGA,120555.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*6B
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$GPRMC,120555.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*7A
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPGGA,120556.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*68
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$GPRMC,120556.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*79
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPGGA,120557.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*69
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$GPRMC,120557.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*78
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPGGA,120558.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*66
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30
$GPRMC,120558.000,V,0000.0000,N,00000.0000,E,000.0,000.0,280606,,,N*77
$GPVTG,000.0,T,,M,000.0,N,000.0,K,N*02
$GPGGA,120559.000,0000.0000,N,00000.0000,E,0,00,0.0,0.0,M,0.0,M,,0000*67
$GPGSA,A,1,,,,,,,,,,,,,0.0,0.0,0.0*30

I'm on a 2nd floor, with my duck antenna and GPS right next to a very large window. My coworker says he gets a signal in his car, so I know they aren't scrambling the signal (I'm on a Navy base right now).

I have the device powered using VBAT, and tried both 3.3V and 5V.

I also tried using the SkyTraq software for it, and the data is coming out fine (I think), its just not getting a fix.

Anyone familiar with this? I'm going to try and take out a laptop later today and try again outside, but doubt it'll work.
Title: Re: problem: my Venus GPS not getting fix
Post by: Soeren on September 28, 2009, 10:56:05 AM
Hi,

It took me 20..30 minutes to get a fix on my Garmin GPS when I was in Belgium last week. This was outdoors, free access to the sky and everything - I've never experienced something like this before.
Wondered if the satellites were being "maintained" or something.
Probably don't help you a bit though.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on September 28, 2009, 12:50:39 PM
Yea, if I was in Europe/Asia, I'd assume just no signal. But I'm in Washington, DC, and like 3 miles away from an international airport.

I just got my new work laptop to try GPS outside, but unfortunately it looks like its about to rain. Doh!

Does the output I got at least look like its the right format? A lot of commas and what looks like hex at the end . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on September 28, 2009, 03:03:28 PM
Problem solved, sorta.

Apparently there were no sats at the time I think. After 18 minutes I only had 2 sats, then suddenly got 6 more in the next few minutes. So the data was all correct.

Then I unpowered everything for ~5 min, then turned it all back on again, and got 8 sats in under 2 minutes. I'm using it near my big window inside.

The altitude and direction seem very fickle . . . but whatever . . .

the results:
By matching it up using Google maps, its accurate within 60 feet. By recording position history, it fluctuated by about 40 feet as it locked on. The realtime 2D RMS over 30 minutes fluctuated up to 15 feet and as low as 1 foot. The datasheet claims to be accurate under 8 feet . . .

Oh, and I'm using a regular duck antenna.
Title: Re: problem: my Venus GPS not getting fix
Post by: c02cutter on September 28, 2009, 05:33:59 PM
Just because you have a window available does not mean you will get signal. In the United States the satellites for positioning are predominately to the south. Most all the satellites are south for all communication in the United States. GPS's need a particular number of satellite fixes for positioning. Depending on software of the unit, it may tell you how accurate it's positioning is at a particular time. A  window can reflect the signal depending on your position to the window from GPS to satellite. GPS's are only as accurate as the the information received and the programming involved in the unit. Another point is that on occasion the satellites are updated and information needs to be downloaded to your GPS for it's programming to position correctly. Since GPS's were opened up to close to military accuracy, acquiring of satellites is a bit more complex.
Title: Re: problem: my Venus GPS not getting fix
Post by: kd5kfl on September 28, 2009, 07:26:39 PM
if a GPS has been off for a while, or has moved 500 or more miles since it was powered on, it has to initialize. figure out where it is, from scratch. takes time.
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on September 28, 2009, 08:38:28 PM
Yea, if I was in Europe/Asia, I'd assume just no signal. But I'm in Washington, DC, and like 3 miles away from an international airport.
Us 'poor' Europeans managed to drag ourselves out of the slime a while ago. Yes - we have 'airports', 'satellites', etc - we even have 'cities' like your 'Washington DC' - but we tend to give them real names rather than acronyms ;-).  We even have windows in our rooms and on our disposable laptops! We also invented quite a lot of stuff: computers, radar, car tyres, jet aircraft etc etc. Sorry - it was just too good let it go!

I live one mile from any other house in the middle of the countryside  - I cant get a cellphone signal but my GPS gets a fix in about 40 seconds.


Does the output I got at least look like its the right format? A lot of commas and what looks like hex at the end . . .
Have sent you you links to formats. But that hex stuff at the end is a checksum. Ignore it at your peril (WebbotCLib uses it) - otherwise you may think you are in Europe one moment and, a few seconds later,  in Thailand.

Cold boot - normally takes a minute or so. Others refer to 20 minutes which is just crazy! Something to check on data sheets though.
Warm boot - the GPS retains some info 'on chip' and so if re-started before it looses the charge then it gets its fix a lot quicker.
Title: Re: problem: my Venus GPS not getting fix
Post by: Kohanbash on September 28, 2009, 08:46:25 PM
Hi
The NMEA strings that you have look correct.
The 20minutes to acquire a good lock I have only seen when moving significant distances (CMU to S. America) or when using commercial corrections (omnistar etc...).

With no corrections the GPS speed and altitude are very coarse.

Where are you getting direction from?

Admin welcome back to the states!
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on September 28, 2009, 08:58:06 PM
All that extra stuff: altitude, direction (compass), speed etc are pretty useless. Guess they are built for cars doing 60mph not a robot going at a snails pace.Think direction and speed may well be calculated from previous readings over time. So 'slow robot' = 'bad readings'. It will all be based on longitude/latitude anyway - and those reading may be a few meters out. May not sound much but if the GPS thinks you've jumped by a meter in 1 second then it will think you are going much faster than you probably are.
Title: Re: problem: my Venus GPS not getting fix
Post by: Kohanbash on September 28, 2009, 09:17:42 PM
Hey
Also you need to be careful if you are writing the driver.
For a reported position of LLMM.mmmmm the LL is degrees and the MM.mmmm is the minutes   
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on September 29, 2009, 07:44:24 AM
if a GPS has been off for a while, or has moved 500 or more miles since it was powered on, it has to initialize. figure out where it is, from scratch. takes time.
I'm trying it out again this morning. It appears the Venus has a *very* slow cold start of 20+ minutes. Arg! Now I understand why there is a VBAT connection - for a battery to avoid cold starts . . .

(the datasheet says 29 seconds, but that just isn't happening)


sdk32285, welcome back to SoR! :P
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on September 30, 2009, 12:46:24 PM
Time-to-first-fix (TTFF) is crucial with these devices.

If its any help I find the modules available from GlobaSat to be very good. http://www.easydevices.co.uk/scp/GPS_Receivers/GPS_Modules.html (http://www.easydevices.co.uk/scp/GPS_Receivers/GPS_Modules.html) with a cold start TTFF of about 45 seconds.

Think that Parallax used one of these in their GPS receiver. http://www.parallax.com/tabid/768/ProductID/396/Default.aspx (http://www.parallax.com/tabid/768/ProductID/396/Default.aspx)

I use the EM-406 module - its just a 1 inch square box (of negligible height) with a cable.

Look at the Parallex link above and its just that thing with the pink border.

The cable output connection is very small and fiddly, and the matching connector from Digitkey is SMD. I just cut off the existing plug and added a Molex connector instead - warning - the lead is only one to two inches long and so doesn't allow you many goes at getting it wrong and the cable is hardwire into the device at the other end. But it saves you the cost of paying someone else to add a mounting board. I just use velcro on the bottom of the device to stick it to my robot.

I get a TTFF of about 45 seconds and I live 'in-the-wild' - but I can still get a signal if the receiver is locked in my desk drawer. Note: the device has a built in aerial so no worries with that.

I recommend this bare module - but replacing the connector with a Molex is not for newbs or people with a faint heart !!

Title: Re: problem: my Venus GPS not getting fix
Post by: Soeren on September 30, 2009, 04:58:59 PM
Hi,

Yea, if I was in Europe/Asia, I'd assume just no signal. But I'm in Washington, DC, and like 3 miles away from an international airport.
And why do you think the Global Positioning System would work differently in Europe or Asia than in Washington?

Usually I get a fix very quickly with my Garmin, a bit faster than my Navman (which isn't slow either).
My point was simply that I had this strange incident where it looked like all the sattellites were switched off for a period.

I am looking forward to the European system however, it should be more up to date on both precision and coverage (probably due to a higher power transmission). And for a number of years, the navigators will be able to receive from both systems, so that will be the right time to shop ;D
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 01, 2009, 06:48:55 AM
Webbot, I already bought 2 Venus GPS modules . . . so kinda stuck for now. But I guess I'll need to try others and compare . . .


Quote
And why do you think the Global Positioning System would work differently in Europe or Asia than in Washington?
My technical friends in Thailand all tell me the GPS signal there is exceptionally weak/bad. I'm not really sure why. Figured maybe some areas are disadvantaged in terms of sat orbits . . .

So uhhh, when will the Euro GPS ever be finished? ;)
Title: Re: problem: my Venus GPS not getting fix
Post by: kd5kfl on October 01, 2009, 08:00:26 AM
http://www.kowoma.de/en/gps/orbits.htm (http://www.kowoma.de/en/gps/orbits.htm)

tell them Thais not to breathe the fumes when they burn the weeds. no reason Thailand should be different from India, Belize or Japan in re gps
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 01, 2009, 08:48:53 AM
http://www.kowoma.de/en/gps/orbits.htm (http://www.kowoma.de/en/gps/orbits.htm)

tell them Thais not to breathe the fumes when they burn the weeds. no reason Thailand should be different from India, Belize or Japan in re gps
Weeds?

I'm not saying they don't get GPS, as I've certainly used an automobile GPS over there without a signal problem. They only told me that the signal is very weak. And I've been told this from several unrelated/connected groups of people. I was planning to test out my Venus GPS over there during my next trip . . .

Anyway, I've been testing it even more, and this Venus GPS really sucks . . . the datasheet says:
Hot start: 1 Seconds
Cold Start: 29 Seconds

but I'm getting more like:
Hot start: 1-2 minutes
Cold Start: 20-30 minutes
This morning I've had it running for 1.5 hours and it still hasn't got a sat lock.

My only theory is perhaps my duck antenna is a bad choice, but the datasheet and Sparkfun both don't recommend any antenna lengths. Wikipedia says 'Civilian use signal, broadcast on the L1 frequency (1575.42 MHz)'. So using this calculator:
http://www.crompton.com/wa3dsp/hamradio/antcalc.html (http://www.crompton.com/wa3dsp/hamradio/antcalc.html)
It suggests 3.6" for half-wave, and 1.8" for quarter-wave. I'm using a 4.5" duck antenna. I've also tried helical antennas meant for 2400 MHz, and a few others around 4"+. Should I find a 3.6" antenna and try again?

What length antennas are you guys using?



Just as a side note, I've noticed that the red LED on the Venus blinks when there is a sat lock.
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on October 01, 2009, 01:55:29 PM
I dont use any antenna at all !!
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 01, 2009, 03:46:39 PM
I dont use any antenna at all !!

not even those built in chip or PCB trace antennas?!
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on October 01, 2009, 05:12:06 PM
Just one of these modules http://www.globalsat.co.uk/product_pages/product_em406.htm (http://www.globalsat.co.uk/product_pages/product_em406.htm)

Has built in antenna etc. So its just plugs into a UART header and off you go.

Check out those acquisition times !
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 02, 2009, 08:26:23 AM
Just one of these modules http://www.globalsat.co.uk/product_pages/product_em406.htm (http://www.globalsat.co.uk/product_pages/product_em406.htm)

Has built in antenna etc. So its just plugs into a UART header and off you go.

Check out those acquisition times !
Did you measure/verify those acquisition times? The Venus *claims* much better times than that . . . I'm just curious.

Also, the accuracy on your GPS is kinda poor (for my application):
Quote
10 meters, 2D RMS 5 meters, 2D RMS, WAAS enabled
I measured the Venus at RMS of 3 meters. At least when it actually has a sat lock . . . :-X
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 02, 2009, 01:05:03 PM
Further investigating the problem, I found something interesting . . .

The Venus datasheet says:
vcc 2.8-3.6V
vbat 1.5V-6V

The sparkfun Venus schematic says vbat and vcc are NOT connected. It says there is a jumper, of which I cannot find. They are also two separate pins. I only use the vbat pin. I've occasionally connected my Venus vbat to 5V regulated, and noticed it was getting strangely too warm. Wasn't sure if that was normal, so I investigated further.

Then I looked at the sparkfun Venus board file - and guess what! vcc and vbat ARE directly connected!

Why the heck they included a vbat pin if its directly connected to the vcc AND not have an schematic, I have no idea . . .

The Venus is probably damaged, and maybe why its not working properly . . .

I'll go rant on the sparkfun site now :P
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on October 04, 2009, 01:25:21 PM
Admin, I am using the same Venus GPS from Sparkfun.

I have come to the decisions it is just flaky. Sometimes i'll get cold starts of seconds, or sometimes 30 minutes. On average it's around 3-5 minutes.

I am using this antenna http://www.sparkfun.com/commerce/product_info.php?products_id=177 (http://www.sparkfun.com/commerce/product_info.php?products_id=177)

I haven't messed with attaching a Vbat, and if i remember correctly, there is a solder bridge on the breakout board you can de-solder if you want a separate Vbat. It is located right off one of the corners of the chip itself, next to a pin header.

Beside that, i am realizing that it may not be as accurate as i need, some testing has shown on my UGV it can vary as much as 50 feet, so my GPS navigating robot will just need BIG fields to navigate until i invest in a better GPS.

I have used their software to set in flash to only output the sentence i need, which saves my Axon from having to parse or deal with all the sentences.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 04, 2009, 06:04:52 PM
Quote
I haven't messed with attaching a Vbat, and if i remember correctly, there is a solder bridge on the breakout board you can de-solder if you want a separate Vbat. It is located right off one of the corners of the chip itself, next to a pin header.
Nope, it has two jumpers, but neither are for VBAT.


I own two Venuses, and decided to try them both at home, about 15 miles from work. I plugged in the first one, the one that I thought was damaged, and it locked on to 3 sats within 5 minutes, and another 4 sats minutes later. Cold start. It was giving me about 50 meters RMS.

Then I plugged in my second Venus, which I haven't yet used before so not damaged or anything. It sat for 1.5 hours and never managed to get more than 2 sats.

For both, I have it sitting on my windowsill with clear skies.

If the Venus datasheet is correct, I'm thinking that maybe SparkFun screwed up the PCB, perhaps adding the wrong components and thats why its working so poorly.

I'm just going to buy another GPS :-\
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on October 04, 2009, 07:36:16 PM
Wow, so i looked closely on mine and found the Vbat jumper (mine has three jumpers) and then compared to the image on Sparkfun, and it's not there!

Here is where it is located on mine (purple circle).
(http://www.billporter.info/img/09133-01-L.jpg)

Time for refund from Sparkfun for selling you and old revision?

Please, let me know if you find another GPS and are happy with it. I might want to replace my Venus sometime soon.

Edit: i just saw on your SparkFun comment about the current issues, sounded like you are powering the GPS off the 3.3V Axon bus? I tried that in the beginning, even though it should work, i was getting sporadic (GPS) resets and poor gps performance when i powered off the Axon. Now it has it's own 3.3V regulator and it hasen't reset or freaked out again. Maybe that could be an issue for you?
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 04, 2009, 07:46:45 PM
Quote
Time for refund from Sparkfun for selling you and old revision?
I wish . . . I bought mine like ~2 months ago if I remember right . . .


I'll probably just buy several and try them all out. It might take a month before I report back, however.
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on October 04, 2009, 07:49:18 PM
Cool, let me know.

Also did you catch my edit?

Edit: i just saw on your SparkFun comment about the current issues, sounded like you are powering the GPS off the 3.3V Axon bus? I tried that in the beginning, even though it should work, i was getting sporadic (GPS) resets and poor gps performance when i powered off the Axon. Now it has it's own 3.3V regulator and it hasen't reset or freaked out again. Maybe that could be an issue for you?
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 04, 2009, 07:56:18 PM
I haven't had any sporadic issues or resets with either my Axon or Axon II. My guess is that they removed/changed the capacitors on your version, resulting in those resets.

I of course also tried regulated 5V with the same problems.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on October 05, 2009, 12:36:56 PM
I'm thinking of getting this module:
http://www.sparkfun.com/commerce/product_info.php?products_id=8266 (http://www.sparkfun.com/commerce/product_info.php?products_id=8266)

Its not SparkFun designed, and has a built in antenna, so I think I can trust those specs. :P

Anyone tried this module and can verify?


Webbot: good thing you no longer have a required 4800bps baud rate in the WebbotLib GPS library. All the latest GPS devices seem to operate at higher baud rates. This one does 38400 at 5 Hz, for example.
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on October 05, 2009, 05:07:26 PM
Admin,

I've used http://www.sparkfun.com/commerce/product_info.php?products_id=8266 (http://www.sparkfun.com/commerce/product_info.php?products_id=8266) and have had much better luck with http://www.sparkfun.com/commerce/product_info.php?products_id=465 (http://www.sparkfun.com/commerce/product_info.php?products_id=465).

Also, it seems like http://www.sparkfun.com/commerce/product_info.php?products_id=9436 (http://www.sparkfun.com/commerce/product_info.php?products_id=9436) is even better, but I've only been playing with it for a few weeks.  If you go with this one, get the adapter from DIY Drones http://store.diydrones.com/PhotoGallery.asp?ProductCode=BR%2D0008%2D01 (http://store.diydrones.com/PhotoGallery.asp?ProductCode=BR%2D0008%2D01).

     Rick Brooks
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on October 05, 2009, 06:18:23 PM
Has anyone tried http://www.parallax.com/tabid/768/ProductID/396/Default.aspx (http://www.parallax.com/tabid/768/ProductID/396/Default.aspx)
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on October 05, 2009, 07:05:56 PM
I am very interested where this thread goes; before i drop $100 on a GPS i want to see it proven by some peers.

Rick<--- What accuracies are you observing with those models? 
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on October 05, 2009, 07:44:13 PM
Madsci,

For short term accuracy, with the EM-406A, I can normally get within one meter of the waypoint.

For long term accuracy (a few hours later) it could be several meters.

    Rick Brooks
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on October 05, 2009, 08:11:11 PM
Hmm, I may get that sooner rather then later.

Let me know when you reach a verdict on the 407; it's datasheet says it's more accurate then the 406's datasheet. (2.5m compard to 10 ) If not, then it won't be worth the $30 over the 406.

It's kind of silly the 407 can track 50 sats when there are not even that many in the sky.
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on December 30, 2009, 11:28:56 PM
Quote
Time for refund from Sparkfun for selling you and old revision?
I wish . . . I bought mine like ~2 months ago if I remember right . . .


I'll probably just buy several and try them all out. It might take a month before I report back, however.

Did you ever find one you like, Admin?
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on January 05, 2010, 12:38:08 AM
Well, I put in an order for one, but where I work shipping takes up to 3 months. Assuming it doesn't get lost in the system . . . government efficiency, you know . . .

I return to work next summer, so hopefully its arrived by then and I can play with it.
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on April 12, 2010, 06:53:13 PM
Just to update everyone.

I removed my Venus GPS from SAGAR and installed a GS407 U-Blox5 GPS.

MAN!!! What a difference. The U-blox is awesome. While I'm running into issues with the accuracy of floating point when parsing my mission file, every time i repeated the mission, it was eerie how identical the same mission ran (Ran into the same car every time, the same spot on the curb, etc).

I recommend the U-blox to any robot builder, and I got it here with a nice adapter board.

http://store.diydrones.com/product_p/spk-gps-gs407.htm (http://store.diydrones.com/product_p/spk-gps-gs407.htm)
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on April 13, 2010, 03:12:51 PM
Madsci,

Are you following the DIYdrone discussions about the U-Blox?  Particularly this one:
http://diydrones.com/forum/topics/for-gs407-ublox5-gps-4hz-diy (http://diydrones.com/forum/topics/for-gs407-ublox5-gps-4hz-diy)

They do mention a new GPS unit that may be even better.

            Rick Brooks
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on April 13, 2010, 04:11:39 PM
Madsci,

Are you following the DIYdrone discussions about the U-Blox?  Particularly this one:
http://diydrones.com/forum/topics/for-gs407-ublox5-gps-4hz-diy (http://diydrones.com/forum/topics/for-gs407-ublox5-gps-4hz-diy)

They do mention a new GPS unit that may be even better.

            Rick Brooks

Lol, that's the one I have and linked to in my last post. I love it.
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on April 13, 2010, 07:21:49 PM
Quote
Lol, that's the one I have and linked to in my last post. I love it.

Which one do you have and love?  The older U-Blox, newer U-Blox, or the Media TeK?

          Rick Brooks
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on April 13, 2010, 07:54:07 PM
This one exactly, bought from the DIYdrones store.

http://store.diydrones.com/product_p/spk-gps-gs407.htm (http://store.diydrones.com/product_p/spk-gps-gs407.htm)

So it's the 407, which is the newer one, I believe.
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on April 13, 2010, 09:17:50 PM
I have one of the older units with 4 Hz update rate.  That is in the robot and I ran it a little last fall.  I should be able to run it more, now that the weather is better.

I did get a Media Tek and that seems to be even better, but I'm not going to stick it in the robot until I run the U-Bloc much more.

         Rick Brooks
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on April 13, 2010, 09:45:15 PM
It's the same unit, different firmware.

I think the consensus in DIY is the older firmware at 2Hz was better (more accurate) then the newer firmware at 4Hz.
Title: Re: problem: my Venus GPS not getting fix
Post by: Rick Brooks on April 14, 2010, 12:28:02 AM
The newer firmware is 2 Hz, the older is 4 Hz, accuracy appears to be about the same.
Title: Re: problem: my Venus GPS not getting fix
Post by: corrado33 on April 18, 2010, 06:40:51 PM
I really don't want to jump into this really complicated conversation.... but as for the altitude on civilian GPS units.  I read a while ago that A. the altitude measurement will never be accurate because of government restrictions (easy to build a GPS system for a missile if it has altitude as well?) and B. that to get a semi decent altitude measurement you pretty much have to be on a plain somewhere because it requires a satellite very near to the horizon, so if you're surrounded by mountains, you're SOL.  Just thought I'd throw in my 2 cents..
Title: Re: problem: my Venus GPS not getting fix
Post by: Webbot on April 18, 2010, 07:22:40 PM
Yep the good ol' USA wants to confuse everyone by making GPS low res for non-military purposes.

They assume everyone else but them is a terrorist!

In the same way as they don't want in-coming missiles to be accurate then they don't want your robots to be accurate either.

So GPS hardware may be 'very accurate' but the 'government' insists that it gives a 'wrong reading'.

But then thats 'the price of freedom' - right?

There are some GPS devices out there which use Russian satellites. Russia seems 'happier' to give real information. Perhaps they cant afford all the hassle involved in giving the wrong answer.

So they are more accurate than US 'big brothered' devices..

NB Above is 'statement of reality' - not a statement of 'ideology'.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on April 18, 2010, 08:12:01 PM
Before we go around bashing the US, and false spreading rumors, the US stopped the GPS reduction in accuracy like 10 years ago. DGPS made GPS so accurate even with the added intentional noise that it didn't matter any more.

Also, the Russian system is really only accurate in and near Russia.

Speaking of bashing other countries, when is Europe ever going to get their 'better' GPS system working? I hear you guys still haven't figured it out ;)
(I'm asking for trouble on purpose)
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on April 18, 2010, 08:28:12 PM
the US stopped the GPS reduction in accuracy like 10 years ago. DGPS made GPS so accurate even with the added intentional noise that it didn't matter any more.

Yes, the US stopped that when Bush became president, so it's been a while. Altitude is very poor because it's even harder to calculate distance to the sats, and requires more sats to determine a 3D fix opposed a simple 2D fix.

Quote
when is Europe ever going to get their 'better' GPS system working? I hear you guys still haven't figured it out ;)

Zing!!! Also, they keep complaining that the US shouldn't have control of ICANN, even though we invented the internet.
Title: Re: problem: my Venus GPS not getting fix
Post by: corrado33 on April 18, 2010, 08:30:27 PM
Before we go around bashing the US, and false spreading rumors, the US stopped the GPS reduction in accuracy like 10 years ago. DGPS made GPS so accurate even with the added intentional noise that it didn't matter any more.

Did I not mention that I read that years ago?   ::) I thought that the reduction was reduced, but I still think altitude on GPS is pretty messed up.  It makes sense though, if you have 5 satelites almost directly above you, there's almost no trigonometrical way to even measure altitude.  (I think)
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 14, 2010, 10:39:54 AM
I've decided to get the U-Blox5 (http://store.diydrones.com/product_p/spk-gps-gs407.htm) that you guys recommended.

Is that $20 adapter a good idea? (It'll be connected directly to my Axon)

I ask because I can't make out the connection on the unit in the single image . . .

(http://store.diydrones.com/v/vspfiles/photos/options/SPK-GPS-GS407-43-T.jpg)
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on June 14, 2010, 11:12:12 AM
Yes, I would recommend it. The GPS itself has some funky micro-miniature board to board connector.

What they don't tell you is you are suppose to epoxy the connector board to the GPS. See my forum post:

http://diydrones.com/forum/topics/ublox-has-bad-connection-with (http://diydrones.com/forum/topics/ublox-has-bad-connection-with)

Super glue worked fine for me.

And just to repeat; it's a super awesome GPS well worth the money. While SAGAR was driving into lakes with the Venus; Now it can navigate crowed parking lots full of parked cars without running into one. And I get locks in my living room while I'm working on code.
Title: Re: problem: my Venus GPS not getting fix
Post by: TrickyNekro on June 14, 2010, 11:16:13 AM
I have had my sharing at finding a nice GPS too...
I got the LS20031...


Cold start in the open could be less that 20 seconds...tested! It has a battery to hold last known satellites...
Hot start can be as short as 1 - 3 sec... And I could see myself moving in a urban area, one meter each direction with
good accuracy...

I won't be spending money anytime soon, for a GPS again, but it's a nice nice choice...
And If I remember right, it was also recommended by some DIY drone guys ;-)

And comes 30$ cheaper... :p
Title: Re: problem: my Venus GPS not getting fix
Post by: Ro-Bot-X on June 14, 2010, 11:42:58 AM
Since the GPSbee (http://www.seeedstudio.com/depot/gps-bee-50-channel-ublox-5-p-560.html?cPath=84_89) from Seeed Studio uses U-blox5, it costs $55 and comes in Xbee form factor I think it's a better deal, as you can get a shield (http://www.seeedstudio.com/depot/xbee%C3%82%C2%AE-shield-v11-by-seeedstudio-p-419.html?cPath=35) or adapter board and plug in whatever "bee" you need at the time. They also make a Bluetooth Bee (http://www.seeedstudio.com/depot/bluetooth-bee-p-598.html?cPath=2) that is cheaper ($23.50!) than a BlueSmirf module... and RFbee (http://www.seeedstudio.com/depot/rfbee-v10wireless-node-with-arduino-inside-p-614.html?cPath=2)...
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on June 14, 2010, 10:50:46 PM
Some of the expense of the DIY drones approved Ublox5 is it's super awesome helix antenna. And either you have to spend more on an antenna for the GPSbee, or it has some crummy on chip antenna that wouldn't compare to the quality helix.

And other units may be recommended by 'some' DIY drone guys, the Ublox5 is the "officially recommended" and official Ardupilot GPS. The Venus taught me my lesson, I'm not going to try to save $20 here or there,  when there's a whole relevant community recommending a single unit.

Now I wish Sparkfun would rewrite their GPS buying guide with actually tested results, not just sum up features on paper.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 15, 2010, 07:53:13 AM
Some of the expense of the DIY drones approved Ublox5 is it's super awesome helix antenna. And either you have to spend more on an antenna for the GPSbee, or it has some crummy on chip antenna that wouldn't compare to the quality helix.
The adapter also has a battery that'll remember sats for a good two weeks - saving you from cold starts. It also has a built in charger to recharge that battery. Now if only they fix that loose connection that requires glue (I plan to try tape).

Quote
And other units may be recommended by 'some' DIY drone guys, the Ublox5 is the "officially recommended" and official Ardupilot GPS. The Venus taught me my lesson, I'm not going to try to save $20 here or there,  when there's a whole relevant community recommending a single unit.

Now I wish Sparkfun would rewrite their GPS buying guide with actually tested results, not just sum up features on paper.
The Venus (chip) is probably as good as it claims. But the Sparkfun breakout board was obviously badly designed and *never* even tested! I didn't bother looking further into it, but they probably didn't properly balance the antenna with a balun, or as people often complain about Sparkfun, they didn't "RTFD" ;D

That said, I'll never trust a Sparkfun GPS unit again. :-X

Spending 50% more to get 100% more is usually a good idea. :P
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 23, 2010, 04:54:22 PM
I'm having GPS issues again, lol . . .

http://www.societyofrobots.com/robotforum/index.php?topic=11447.0 (http://www.societyofrobots.com/robotforum/index.php?topic=11447.0)
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 23, 2010, 05:45:35 PM
madsci, did you just use a duck antenna with the Venus like me?

A guy in the comments section on SF said this worked great:
http://www.sparkfun.com/commerce/product_info.php?products_id=464 (http://www.sparkfun.com/commerce/product_info.php?products_id=464)
Then again, SF could have changed the design before Feb 2010 when the guy posted . . .

someone else said:
Quote
My two boards had badly mismatched inputs--2 dB return loss. Was able to tune with 5pF capacitor in shunt. Sensitivity is poor, but works OK with active antenna when outside. Takes a very long time to first fix when signal is weak.

I've abandoned the Venus already, but I'm suspecting its an antenna problem . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on June 23, 2010, 06:53:23 PM
I used this one

http://www.sparkfun.com/commerce/product_info.php?products_id=177 (http://www.sparkfun.com/commerce/product_info.php?products_id=177)

But still, I remember it reporting good signal strengths, just crappy calculations and long fix. The Ublox really does blow me away.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 24, 2010, 07:56:14 AM
I used this one

http://www.sparkfun.com/commerce/product_info.php?products_id=177 (http://www.sparkfun.com/commerce/product_info.php?products_id=177)

But still, I remember it reporting good signal strengths, just crappy calculations and long fix. The Ublox really does blow me away.
Thats the one a SF rep suggested using in a forum post on the Venus page. But the way he worded it sounded like they didn't actually try using it . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 on June 24, 2010, 12:46:57 PM
I wouldn't take anything from SparkFun without a grain of salt.

They are still very much a 'started in a garage' company. Between shipping mistakes, evil(or idiotic) marketing ploys, mistakes in products and poorly thought out designs I try my best to avoid them. I have either saved money buying somewhere else or supported DIY websites like DIYDrones.

But they do have a competition I want to enter. Have to give them that.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin on June 24, 2010, 01:03:32 PM
They've served me well, except the Venus incident . . . and the bluetooth incidents . . . I still buy from them often.

That said, they refuse to sell my Axons unless I mark them down to $60 each >:(
They insist no one would ever buy an Axon at my price . . . lol . . . They completely ignored me about the Axon II . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 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.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 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.
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 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.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 (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 . . .
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 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 (http://www.sparkfun.com/commerce/product_info.php?products_id=9566) was the one that had the hiccup, not ours.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 (http://www.sparkfun.com/commerce/product_info.php?products_id=9566) 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.

(http://static.sparkfun.com/images/products/00465-03-L_i_ma.jpg) (http://store.diydrones.com/v/vspfiles/photos/SPK-GPS-GS407-2T.jpg)
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 (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 (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?
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 (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.
Title: Re: problem: my Venus GPS not getting fix
Post by: madsci1016 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?
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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.
Title: Re: problem: my Venus GPS not getting fix
Post by: Admin 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 (http://www.societyofrobots.com/robotforum/index.php?topic=13739.0)