Parallax Gps giving weird Long Lat Points

TylerSkyler · 2012-03-11 10:46

Hello All! I'm using a Parallax Gps for reading gps data(This One). Using this code I'm continually printing Longitude and Latitude:

Pub Main
repeat
  Debug.str(string("Longitude : "))
  lon2 := GPS.GetLongitude
  Debug.str(FS.FloatToString(lon2))
  Debug.str(string(" degrees",13))
  Debug.str(string("Latitude : "))
  lat2 := GPS.GetLatitude
  Debug.str(FS.FloatToString(lat2))
  Debug.str(string(" degrees",13))
  waitcnt(clkfreq + cnt)

All of the variables are declared in VAr. This prints values to the terminal. But the values are completely erratic jumping from .1degree to degrees in one debug. The light on the module is solid and it is reading in smart mode with the GPS_SmartMode object in the obex. some said it needed to be moving to get good values so I drove it around my block then plotted the points and they were skattered all over europe(im in California

). Why would this be? How can I fix it?

As Always...Thanks,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-11 10:52

Are you sure that GetLongitude and its mate return floating-point values? Perhaps they're integer with an assumed decimal point location. What happens if you use Debug.dec to print them out?

-Phil

TylerSkyler · 2012-03-11 11:16

Thanks for the reply. I changed it to Debug.dec() and ran the program again and I got this:

Longitude : 1113523308 degrees
Latitude : 1110657089 degrees


Longitude : 1108090073 degrees
Latitude : 1100105870 degrees


Longitude : 1110653863 degrees
Latitude : -1035524249 degrees


Longitude : 1095952913 degrees
Latitude : 1111984838 degrees


Longitude : 1112500388 degrees
Latitude : 1112270057 degrees


Longitude : 1111697261 degrees
Latitude : 1084938900 degrees


Longitude : 1112212481 degrees
Latitude : 1112246983 degrees


Longitude : 1108664015 degrees
Latitude : 1112505874 degrees


Longitude : 1120935621 degrees
Latitude : 1099208876 degrees


Longitude : 1117023207 degrees
Latitude : 1092237621 degrees


Longitude : 1113783530 degrees
Latitude : 1112517303 degrees


Longitude : 1111959963 degrees
Latitude : 1110730917 degrees


Longitude : 1113042376 degrees
Latitude : 1084309418 degrees


Longitude : 1115971052 degrees
Latitude : 1075141855 degrees


Longitude : 1118326528 degrees
Latitude : 1117222776 degrees


Longitude : 1112859211 degrees
Latitude : 1117963620 degrees


Longitude : 1117941103 degrees
Latitude : 1117618742 degrees


Longitude : 1111697037 degrees
Latitude : 1111181377 degrees


Longitude : 1110787714 degrees
Latitude : 1110730924 degrees


Longitude : 1112238244 degrees
Latitude : 1111207144 degrees


Longitude : 1118667429 degrees
Latitude : 1113299927 degrees


Longitude : 1112999131 degrees
Latitude : 1070051228 degrees


Longitude : 1111194048 degrees
Latitude : 1089507385 degrees


Longitude : 1110135134 degrees
Latitude : 1107877588 degrees


Longitude : 1115831462 degrees
Latitude : 1115691179 degrees


Longitude : 1084683893 degrees
Latitude : 1092392576 degrees


Longitude : 1108496028 degrees
Latitude : 1094892462 degrees


Longitude : 1112887997 degrees
Latitude : 1113805489 degrees


Longitude : -1035783366 degrees
Latitude : 1117618742 degrees


Longitude : 1110147794 degrees
Latitude : 1113025570 degrees


Longitude : 1111692549 degrees
Latitude : 1116303990 degrees


Longitude : 1110670530 degrees
Latitude : 1112474957 degrees


Longitude : 1113554218 degrees
Latitude : 1112255733 degrees

Even If I assumed a decimal place it isn't close to my location(i have found it on my gps). Any other ideas?

Thanks,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-11 11:58

Are you sure that the GPS_SmartMode object that you're using was written for your GPS and not an earlier model? The only one I can find online was written in 2007. Please post the GPS_SmartMode object that you're using.

-Phil

TylerSkyler · 2012-03-11 13:39

The one I'm using was written in 2007, but the BS2 demo for the new and old GPS module are the same. It seems therefore that the Propeller demo written for the other should be acceptable. Correct me if i'm wrong please.

Thanks,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-11 13:56

The 2007 version I'm looking at uses 4800 baud and sends commands to the GPS in the form "!GPS". That's both the wrong baudrate and wrong command for the GPS unit that you have. So, again, please post the object that you're using.

-Phil

GordonMcComb · 2012-03-11 14:19

Use this to test. It was written for and tested with the VPN1513 unit. Note it uses 9600 bps to communicate with the GPS unit rather than 4800 of the older model. As Phil surmises, this is very likely your problem. No additional objects are required other than those that come with the Propeller tool. The output is Google Maps friendly.

!GPS is still the command word to use with this unit. Not sure what Phil was looking at there.

Please also note the unit requires 5V to 12V (won't run reliably at 3.3V as it has its own 3.3V voltage regulator) but its I/O pin is 3.3V friendly, having already a suitable 1K series resistor.

OBJ

  PST    :  "FullDuplexSerial"
  GPS    :  "FullDuplexSerial"

CON

  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000

  GetLat   = $05
  GetLong  = $06

PUB main 

  PST.start(31, 30, 0, 115200)
  GPS.start(0, 0, 00, 9600)                ' GPS connected to pin0
   
  repeat
    GPS.str(string("!GPS"))                   ' GPS command header
    GPS.tx(GetLat)                            '  for latitude  
    WriteVal
   
    PST.str(string(",")) 
    GPS.str(string("!GPS"))                   ' GPS command header
    GPS.tx(GetLong)                           '  for longitude 
    WriteVal
    PST.str(string(13))
    WaitCnt(ClkFreq + Cnt)                    ' Wait 1 second
  
PRI  WriteVal | Degrees, Minutes, MinutesD, Dir, workVal

  WaitCnt(ClkFreq / 10 + Cnt)                 ' 1/10 second wait

  Degrees := GPS.rx                           ' Retrieve bytes from GPS
  Minutes := GPS.rx
  MinutesD := (GPS.rx << 8) | GPS.rx
  Dir := GPS.rx==1
  
  if dir == -1                                ' If Dir = -1, prepend - sign
    PST.str(string("-"))
  PST.dec(Degrees)
  PST.str(string("."))

  workVal := (Minutes * 1000 / 6) + (MinutesD / 60)
  PST.dec(workVal)

-- Gordon

TylerSkyler · 2012-03-11 14:37

@Phil- sorry i don't have access to my computer right now that is why I wasn't able to post the object, but it is the one written in 2007 that you mentioned.

@Gordon- thanks I'll look at that code when I get a chance(I'm responding on my iPod touch right now). I'll post the results of your code. Wish me luck!

As always Thanks,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-11 15:26

GordonMcComb wrote:

!GPS is still the command word to use with this unit. Not sure what Phil was looking at there.

Odd that "!GPS" is not mentioned in the 28506 PDF anywhere. All that's listed there are command codes ranging from 0x00 to 0x0A.

-Phil

TylerSkyler · 2012-03-11 21:04

@Gordon I tested out your code and it just gave me 33.12175 for the longitude and latitude over and over again. It's very strange. Do you know why this is? and how could it be fixed??

Thanks,

Tyler

Ken Gracey · 2012-03-11 21:44

Hey Tyler, it's really odd that the GPS reports data and that the data is incorrect. As you guys continue to debug this system, feel free to drop me a line if you think you need a replacement to this unit. It seems like a code situation but we don't make these chips [just source them] so I really couldn't definitively say that it's entirely functional. However, that particular unit would have passed our internal tests to properly identify its location after it was manufactured.

Ken Gracey

GordonMcComb · 2012-03-11 22:50

TylerSkyler wrote: »

@Gordon I tested out your code and it just gave me 33.12175 for the longitude and latitude over and over again. It's very strange. Do you know why this is? and how could it be fixed?

It could be in the formatting of the code. Compare the indenting shown in the code here with yours. As you didn't provide the actual output (you can copy and paste, as you did before) it's hard to know from just your short description. It helps if you're as specific and complete as possible.

Apart from that, is 33.12175 correct for your latitude? That would be helpful info. (Or is it your longitude, and you're in eastern Europe or some such?)

You can also switch to /RAW mode, and just read the sentences as they stream into the Propeller. This is a great way to verify proper operation of any GPS module.

Phil, The docs on this one are a little scant. The BS2 code was updated (the main change was the baud rate), but for whatever reason the additional detail that was in the 28146 docs were omitted for the replacement unit.

-- Gordon

TylerSkyler · 2012-03-11 23:17

@Gordon- Thanks here's the output:

33.12175, 33.12175

33.12175, 33.12175

33.12175, 33.12175

33.12175, 33.12175

33.12175, 33.12175

33.12175, 33.12175

33.12175, 33.12175

No my position isn't 33.12175 lat or long(I'm in California). The you provided code seems to reports data even when the gps isn't connected. The wire to the antenna is very loose and I'm worried that the gps antenna isn't send data to the module or being grounded properly. Would the gps light go solid even if the gps antenna isn't enjoying a good connection?

@Ken- Thanks for the info. If it is deemed to be a bad module I'll have it replaced, but I how it is user error on my part

Thanks,

Tyler

GordonMcComb · 2012-03-12 09:34

TylerSkyler wrote: »

No my position isn't 33.12175 lat or long(I'm in California).

That latitude is valid for California (north San Diego county, parts of Imperial county), so without knowing what it's supposed to be anything I suggest is just guessing.

The only thing I can say is to check the usual things:

1. Don't connect /RAW (let it float high, so it's in Smart Mode).
2. Be sure you're powering it from an *adequate* 5V supply (not 3.3V)
3. Recheck the wiring to the GPS (the example I provided assumes the GPS is on pin 0.)

etc.

You may also want to simply try receiving the GPS in raw mode at 4800. Pull /RAW low, reset power to the GPS, and see if you get what looks like valid sentences. You'll see sentences that should include your location (but it's not Google Maps ready).

The antenna on this is a bit loose (I wouldn't classify it as "very loose"). It just snaps on. If you get satellite lock within a minute or so then it should be fine.

-- Gordon

TylerSkyler · 2012-03-12 09:53

@Gordon- Thanks i'll check all that when I get a chance. My Location is 35,-118(Approximately) so neither Lat or Long was right. I'll check those things and try again.

Thanks,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-12 10:10

Gordon McComb wrote:

You may also want to simply try receiving the GPS in raw mode at 9600.

I assume you meant to say "4800." According to the doc:

"RAW: Selected by pulling the /RAW pin LOW. When low, the module outputs raw NMEA0183 strings @ 4800 baud."

-Phil

GordonMcComb · 2012-03-12 11:26

Phil Pilgrim (PhiPi) wrote: »

I assume you meant to say "4800."

Yes, that's correct. Should be 4800 baud. I edited original post as well.

-- Gordon

GordonMcComb · 2012-03-12 11:51

TylerSkyler wrote: »

@Gordon- Thanks i'll check all that when I get a chance.

I looked at the posted code and I see the forum software lobbed off some characters. The line should read:

GPS.start(0, 0, (percent sign)1100, 9600)

where the (percent sign) is %.

In case there's anything else missing I'm posting it, as well.

For a more robust test, you might want to go back to the smart mode object you started out with, changing it to 9600 baud (edit GPS_SmartMode.spin), and trying that again. That demo provides more data. The one I posted just gives latitude and longitude only.

-- Gordon

Phil Pilgrim (PhiPi) · 2012-03-12 12:05

GordonMcComb wrote:

I don't know why the got chopped off. In case there's anything else missing I'm posting it, as well.

That's really weird. I was all ready to send Bump an email about it. But, when I tried it myself, I couldn't get it to screw up:

OBJ

  PST    :  "FullDuplexSerial"
  GPS    :  "FullDuplexSerial"

CON

  _clkmode = xtal1 + pll16x
  _xinfreq = 5_000_000

  GetLat   = $05
  GetLong  = $06

PUB main 

  PST.start(31, 30, 0, 115200)
  GPS.start(0, 0, %1100, 9600)                ' GPS connected to pin0
   
  repeat
    GPS.str(string("!GPS"))                   ' GPS command header
    GPS.tx(GetLat)                            '  for latitude  
    WriteVal
   
    PST.str(string(",")) 
    GPS.str(string("!GPS"))                   ' GPS command header
    GPS.tx(GetLong)                           '  for longitude 
    WriteVal
    PST.str(string(13))
    WaitCnt(ClkFreq + Cnt)                    ' Wait 1 second
  
PRI  WriteVal | Degrees, Minutes, MinutesD, Dir, workVal

  WaitCnt(ClkFreq / 10 + Cnt)                 ' 1/10 second wait

  Degrees := GPS.rx                           ' Retrieve bytes from GPS
  Minutes := GPS.rx
  MinutesD := (GPS.rx << 8) | GPS.rx
  Dir := GPS.rx==1
  
  if dir == -1                                ' If Dir = -1, prepend - sign
    PST.str(string("-"))
  PST.dec(Degrees)
  PST.str(string("."))

  workVal := (Minutes * 1000 / 6) + (MinutesD / 60)
  PST.dec(workVal)

Which browser and OS are you using?

-Phil

GordonMcComb · 2012-03-12 12:32

Phil Pilgrim (PhiPi) wrote: »

Which browser and OS are you using?

Try editing your post, and see what happens.

Anyway, I'm using WinXP/SP3 and Firefox (latest whatever). Funnily enough, I get a Unicode symbol box when I view your quote of my post in Firefox, and nothing (a blank space) when I view in Chrome. (Same characters appear in View Source). However, your post of the code shows the percent character.

Same thing happens when I view the page on a Mac with Firefox.

Maybe you have extra posting privileges, being a VIP and all.

Just to test, I'm going to post the line again with the percent sign, and leave it to see what happens now (I won't edit this post either way):

GPS.start(0, 0, $1100, 9600)

-- Gordon

Phil Pilgrim (PhiPi) · 2012-03-12 13:12

Gordon,

I edited my post, and nothing changed. I, too, am using WinXP/SP3 and latest Firefox. I use the plain-text editor, though, not the fancy one. Maybe that's the difference. BTW, your percent sign got changed to a dollar sign in your previous post.

-Phil

cavelamb · 2012-03-12 13:44

Really dumb obvious question to the O.P.?

You ARE outside when you run this?

GordonMcComb · 2012-03-12 16:08

On this unit the satellite lock LED is (I think) under the control of the Prop chip on the board. If the satellites are in lock, the data should be good. However, this could be an issue with the firmware. I had only one unit to test, and it seemed to lock quickly, and indoors. My location indoors is typically within 4-5 feet of a window, and my house uses wood construction and older paper-backed fiberglass insulation. Offices and homes with aluminum construction, and/or aluminum-backed insulation, may not fare as well.

In my tests, accuracy with this unit was always within six feet of my actual location inside my house, as displayed in Google Maps. In fact, it was always more accurate than the GPS in my iPhone. With my iPhone I apparently live two houses down the street.

Try the revised code with the proper mask for the serial port setup. That might do it. Download the spin file itself to avoid any possible errors in formatting of the posted code.

-- Gordon

GordonMcComb · 2012-03-12 16:11

Phil, I posted some tests in the Test forum. I got the problem again when I edited the post. This might be an issue related to posting privileges.

-- Gordon

TylerSkyler · 2012-03-12 16:29

@Gordon- Thanks the updated code works perfectly! I think that it was the lack of the percent as you said in your post. Hopefully soon i'll be give back to the propeller community(Im a noob

).

Thanks Again,

Tyler

Phil Pilgrim (PhiPi) · 2012-03-12 16:30

Gordon,

I don't have any special or unique posting privileges. Are you using the fancy editor, or the plain text editor? If the former, try the latter to see if there's any difference.

Tyler,

'Glad you got it working!

-Phil

GordonMcComb · 2012-03-12 18:32

Looks like it was the enhanced editor. I'll make a new test in the Test forum, again with editing the post afterward, and we'll see what we'll see.

Tyler, Glad it's working now. This GPS is a nice unit, especially as you can tweak the firmware. The existing code is on the shopping page for the GPS. It's not commented much (if at all) though. It's not terribly complicated, fortunately.

-- Gordon

TylerSkyler · 2012-03-14 09:29

Hello All! Sorry to reawaken this thread, but i'm trying to get the heading now. What do I have to do to recieve this as it isn't a number it is a "Word"(according to the documentation). What would be the procudure to recieve a word from the module?

Thanks,

Tyler

GordonMcComb · 2012-03-14 09:48

The module sends one byte at a time, so you send the command request for heading, then receive two bytes. The two bytes together make a word. You need to shift the first (high) byte into the variable, then add (or OR) the low byte. The code I posted earlier demonstrates this for the decimal minutes value:

MinutesD := (GPS.rx << 8) | GPS.rx

Note that heading is usually not accurate unless you're moving, and even then, it's still often off by several degrees. So if you get incorrect or inconsistent results that's probably the reason. You need a magnetometer to get accurate compass headings.

For other values returned and how to handle them look at the smart gps object you originally started with.

-- Gordon

Parallax Gps giving weird Long Lat Points

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