D2523T Problem

GPS/GNSS Development Boards
1

OK I am either an real doofus or just missing somthing but definately am in need of some help. You can decide what kind??

I bought a D2523T GPS module and have it connected to an Mini ARM 2440 TTL Serial Port. I am receiving data no problem at 9600,8,N,1. The problem id that the GPS wont get a fix or much else for that matter. I logged some of the data and it does look like the GPS time is there but there is not much else. Here is a copy and paste of it.

$GPVTG,N*30

$GPGGA,050446.00,0,00,99.99,*65

$GPGSA,A,1,99.99,99.99,99.99*30

$GPGSV,1,1,01,23,33*79

$GPGLL,050446.00,V,N*49

$GPRMC,050447.00,V,061010,N*79

$GPVTG,N*30

$GPGGA,050447.00,0,00,99.99,*64

$GPGSA,A,1,99.99,99.99,99.99*30

$GPGSV,1,1,01,23,34*7E

$GPGLL,050447.00,V,N*48

$GPRMC,050448.00,V,061010,N*76

CLIPED SOME OUT BUT LOG WAS CONTINUOUS.

$GPVTG,N*30

$GPGGA,063008.00,0,00,99.99,*6B

$GPGSA,A,1,99.99,99.99,99.99*30

$GPGSV,1,1,01,19,29*7B

$GPGLL,063008.00,V,N*47

$GPRMC,063009.00,V,061010,N*77

$GPVTG,N*30

$GPGGA,063009.00,0,00,99.99,*6A

$GPGSA,A,1,99.99,99.99,99.99*30

$GPGSV,1,1,02,07,25,19,28*79

$GPGLL,063009.00,V,N*46

$GPRMC,063010.00,V,061010,N*7F

$GPVTG,N*30

$GPGGA,063010.00,0,00,99.99,*62

$GPGSA,A,1,99.99,99.99,99.99*30

Note the time of each packet. Ticking along quite fine. Please tell me I neglected to read the right part of the manual… I didnt hook up the Ubloks Config yet as I understood that there should be full NMEA Date comming out already… Please help…

2

Hi,

I am using the same module for a couple of days now, and here it gets a fix indoors just fine.

You must however allow it for some time (I think mine took 10 minutes) to get a fix, preferably with the antenna outside looking at a clear sky so I would try that first.

Question: how much current is your module using? I am having a problem with mine where the current just increased with 100mA to almost 200mA during acquisition…

good luck!

3

If you care to take a look at the attached log you will see that I had it running quite a while. About an hour and it was outside where my other GPS devices had no problem. Time stamps will be broken because of my turning the logging on and off as it was filling my memory too fast.

Cant say I have measured the current demands. Perhaps I should as I think I may be looking at potential damage should it go over 200mA. Did you have any need to connect it to a PC and set it up or are you just using it out of the box?

I am also surprised that yours took 10 minutes to get a fix. I believe the Cold Start should get a fix in less than 2 minutes. If it was running in the last 4 hours then it should be as little as a few seconds.

4

Hi,

sorry did not look at your log! I am using the receiver indoors (top floor though) so that probably explains why it takes so long. Have not yet tried outside (have to move the lab outside but it’s raining now hehe).

I used the U-center software because for me that was the easiest way to capture the NMEA data. And I want to use it in an application that requires 4800Bd instead of the 9600Bd default data rate, but for the rest I am using it out of the box (it worked out of the box).

Good luck!

5

Yes being indoors would explain it. Good luck to you also with the current issue…

6

Not sure if you solved this yet, but if you look at the messages the reciever never acquires even a single bird. Have you tried another location? (Across the street, down the block, etc)

Some information Breakdowns from your data

$GPGGA,050446.00,0,00,99.99,*65

050446.00 -Fix taken at 05:04:46.00 UTC

(blank) -Latitude

(blank) -Latitude Direction (N/S)

(blank) -Longitude

(blank) -Longitude Direction (E/W)

0 -Fix Quality is 0 – Invalid (You want a value between 1 & 5)

00 -Number of satellites being tracked

99.99 -Horizontal dilution of position (error)

$GPGSA,A,1,99.99,99.99,99.99*30

A -Automatic selection of 2D/3D fix

1 -No Fix

(multiple blanks) -PRNs of sats used in fix

(multiple) 99.99 -dilution of precision (error)

7

Yep that is exactly why the thread has been started. Messages from support suggest that I may have a defective device. Unfortunately I wont be able to deal with it for quite a while as I am leaving on the trip I bought the device for today. Just lucky I happen to have a Garmin GPS16 Puck laying about. Before I send it back I plan to try and reset it with their software by flashing it with the manimal output strings that I need. I should get away with GPGGA. Thanks all for the replies.

8

For future debugging help, let me add that all of the GPS modules I’ve used will cheerfully increment their notion of the current time in the NMEA messages even if they never see a satellite. The modules I’ve used also won’t start telling you about satellites until they do have a fix.

9

Hi

When connecting up GPS please remember the following.

  1. Power supply needs to be very clean and noise free. If you can, then supply the GPS from a seperate regulator. In most cases the GPS is being run in a make or break situation. A little more noise and it wont work at all, a little less noise and it would work like there was never a problem. Clean Supply is major issue. Also most GPS will fail to startup properly if your supplies current ability is not enough to give them the current surge they need to start. For example a GPS drawing 100mAH normally may draw upto 300mA for a very short time (lets say a milli second) at startup. So please make sure that you over specify your regulator and current source (i.e battery, e.g a large 3V button cell will usually peat at 60mA, any more current drawn from it and its voltage will colapse. )

  2. Proper decoupling of the device is also nessasary. Just adding a 100nF sometimes is not enough.

  3. Try using shorter wires to regulator as possible.

  4. Avoid using switched regulators as they are usually very noisy.

hope this helps