[SOLVED] SIMCOM SIM548c-EVB with SIM908C gives wrong Latitude from AT-CGPSINFO=2 command

Johanvz said:

Hello everyone,

I'm new to working with SIMCOM units and I have a question to anyone that knows the SIM908 module. I'm currently working with it on the SIM548C-EVB board and I am getting the wrong GPS latitude reading.


The commands and output:

AT+CGPSSTATUS?
+CGPSSTATUS: Location 3D Fix

OK
AT+CGPSINF=2
2,065540,1564.857861,S,2450.196523,E,1,9,0.918522,1536.112427,M,22.779541,M,,000
OK

Now for the Latitude, the value 1564.857861,S is incorrect? As it is in the format ddmm.mmmmmm but the minutes part is out of range as it should not be more than 60 anyway. Ontop of that, the actual value that I am expecting is 2604.851567,S and not 1564.857861,S. The longitude value is 100% correct.

If I look at the output ont he debug port, the values are all correct, so it is just from the AT command when I query the value that it is incorrect.

Sample from debug UART:

$GPGGA,074001.000,2604.851567,S,02450.202795,E,1,8,1.00,1548.101,M,22.780,M,,*7E
$GPGLL,2604.851567,S,02450.202795,E,074001.000,A,A*45

Any suggestions would be welcome.

Oh, the version info:
AT+GSV
SIMCOM_Ltd
SIMCOM_SIM908
Revision:1137B02SIM908M64_ST

Thanks in advance for you help.

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Echo wang said:

Your module's version is B02, pls update to B03, it can solve your problem.

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gosurata said:

Hi, do you know where i can find the firmware and the updater tool ?. Thanks in advance.

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gosurata said:

I've got the b02 version of the firmware, im not who opened this thread, but i had similar problems.
I found out, the data showed by the device was indeed correct, the problem was the format. The datasheet says than the coordinates are in format ddmm.mmmm , and that's wrong. The given format by the device is mmmm.mmmmm. After a while i realized that, and coulde parse the coordinates correctly. Im working on a gps tracker, for an academic assignment. I dont think i will update the firmare due to damage something, time is running, and this devices are rare and expensive in argentina (~70 u$s). But, it would be usefull to anyone who google "how to" or "where to", to upload the tools somewhere.
There is not much usefull information out there, and it could be great, if we start sharing info and "walkthroughts" about how to use sim908.
Thanks in advance, and apologies for my english.

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Echo wang said:

Hi, gosurata,
I can understand you.Never mind!
If you do not want to update the firmware, pls get the GPS information from GPS/DBG-TXD、GPS/DBG-RXD, but not AT.

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gosurata said:

I dont understand this: i am reading the gps from the serial port, (RXD, TXD), the data im reading is correct why should i use GPS-DBG port? . I have just to adjust the parsing program i will use to adquire that data, because of the "error" in the format given by the device (but i suspect than the problem was in the translation of the documentation).
After i finish some part of the project i am working, i try to upload there, with some points. It could help future developers to get a "start point" to get a functional sim908, without the evaluation kit. (I am working without it, i just -welded- little coper wires from the chip pins, to a square test board surronded by pins). Until then thanks you very much!.

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Echo wang said:

Your module's version is B02, pls update to B03, it can solve your problem.

Click to expand...

AT+GSV
SIMCOM_Ltd
SIMCOM_SIM908
Revision:1137B03SIM908M64_ST

OK
AT+CGPSINF=0
0,-116.307060,5146.339662,71.616142,20120731145145.000,257,12,0.000000,88.816719
OK
AT+CGPSINF=32
32,150007.000,A,5146.339662,N,116.307060,W,0.00,88.82,310712,,E,A
OK

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markwj said:

I have B03 firmware, but similar problem:



My location should be 51.77XXXX,-1.27XXXX

I have to use AT commands to poll GPS, due to limited number of async ports in the existing hardware platform I am using.

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Echo wang said:

Hi, Markwj, pls offer a e-mail to me, I send the file to you about your question.

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markwj said:

I PMed you my address. Is there newer firmware?

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Echo wang said:

I have send to you, not newer firmware. pls check your e-mail.

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markwj said:

Got the document. Thanks. Very useful.

I see the problem is the SIM908 gives the coordinates in ddmm.mmmmmm format, but my other tools gives it in decimal. Converting the degrees and minutes with https://transition.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html/ shows them to match, so I'm happy and can now work out how to do that in PIC 8bit code...

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markwj said:

Got the document. Thanks. Very useful.

I see the problem is the SIM908 gives the coordinates in ddmm.mmmmmm format, but my other tools gives it in decimal. Converting the degrees and minutes with https://transition.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html/ shows them to match, so I'm happy and can now work out how to do that in PIC 8bit code...

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rajath s said:

Can u please tel me what is cost of sim548-evb board and where did u buy. I am also in need of it. And what about sim908, which one is best sim548c or sim908

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