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santiagolopez
 
Posts: 8
Joined: Wed Jan 25, 2017 8:58 am

I can't get the GPS signal.

by santiagolopez Fri Feb 17, 2017 12:01 pm

Hi all,
I'm trying to get the GPS signal with a TD1205p but I have some problems.

I have loaded the td1205P_modem_SOFT2067.bin firmware with TDloader.exe. I can acces to the device via serial:
image001.png
image001.png (29.56 KiB) Viewed 450 times

But, when I have tryed to get the GPS signal with the AT command: AT$GPS=1,16,0,65535,1,1 I don't get any information.
image002.png
image002.png (42.02 KiB) Viewed 450 times

also with this command: AT$GPS=1,4,900,180,2,2
I never get any GPGGA response
image003.png
image003.png (9.37 KiB) Viewed 450 times


I don't know what i'm doing wrong, Can anybody helpme?
aoc
 
Posts: 7
Joined: Tue Aug 02, 2016 2:44 pm

Re: I can't get the GPS signal.

by aoc Fri Feb 17, 2017 4:01 pm

Hi,

First of all, I am not using TD1205P, but I guess TD GPS functions are the same.

santiagolopez wrote:But, when I have tryed to get the GPS signal with the AT command: AT$GPS=1,16,0,65535,1,1 I don't get any information.

The hdop can't be zero as dilution of precision won't be null. A value of 500 is quite correct.
The 16 satellites in view may be too much. A value of 4 or 5 is enough.

santiagolopez wrote:also with this command: AT$GPS=1,4,900,180,2,2

Here, the timeout may be too short. The GPS chip requires at least 30 seconds to get a position after a cold start.
If you're testing indoor, geolocation can be very long or might not succeed. You should test outdoor.
Also, the GPS antenna should be upward.
santiagolopez
 
Posts: 8
Joined: Wed Jan 25, 2017 8:58 am

Re: I can't get the GPS signal.

by santiagolopez Mon Feb 20, 2017 8:48 am

Thanks you aoc. I will try with your indications. But these commands are from official documentation of TD1205p and I suppose there are correct.
aoc
 
Posts: 7
Joined: Tue Aug 02, 2016 2:44 pm

Re: I can't get the GPS signal.

by aoc Mon Feb 20, 2017 10:11 am

The second example will definitely work for outdoor applications.
Using GPS indoor, you should either increase hdop or timeout.
santiagolopez
 
Posts: 8
Joined: Wed Jan 25, 2017 8:58 am

Re: I can't get the GPS signal.

by santiagolopez Mon Feb 20, 2017 3:22 pm

aoc wrote:The second example will definitely work for outdoor applications.
Using GPS indoor, you should either increase hdop or timeout.


I just have tried in outdoor and the results are the same, I don't get any GPS signal. I only get the time, but not the localization. What am I forgetting?
aoc
 
Posts: 7
Joined: Tue Aug 02, 2016 2:44 pm

Re: I can't get the GPS signal.

by aoc Thu Feb 23, 2017 3:54 pm

I don't know how I can help.
Being indoor, 1 meter from a large window, I have tried AT$GPS=1,4,1000,65000,1,1 on my TD1204 EVB and I have got a position in 5 minutes.
I tried the same command 15 minutes later and couldn't get any position in 20 minutes.
santiagolopez
 
Posts: 8
Joined: Wed Jan 25, 2017 8:58 am

Re: I can't get the GPS signal.

by santiagolopez Thu Mar 02, 2017 1:38 pm

aoc wrote:I don't know how I can help.
Being indoor, 1 meter from a large window, I have tried AT$GPS=1,4,1000,65000,1,1 on my TD1204 EVB and I have got a position in 5 minutes.
I tried the same command 15 minutes later and couldn't get any position in 20 minutes.


I have a question, when you send the AT command, you get an OK answer immediately? I can't understand why I can't get the GPS signal... I have tried with three different boards.
aoc
 
Posts: 7
Joined: Tue Aug 02, 2016 2:44 pm

Re: I can't get the GPS signal.

by aoc Tue Mar 07, 2017 2:43 pm

santiagolopez wrote:I have a question, when you send the AT command, you get an OK answer immediately?

Sometimes yes, sometimes almost.
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