No GPS fix with AirPrime MC7355

IoT Modules MC/EM Series
1

Hello,

I am trying to configure the MC7355 board in order to get a GPS fix using the GobiSerial driver. After many tries, the module seems not to be able to catch a fix in Standalone mode (timeout error returned by AT!GPSSTATUS?). I have issued the following commands to the module :

AT!GPSTRACK=1,255,5000,1000,10
or
AT!GPSFIX=1,255,5000

I have 2 antennas, both active. So I expect I must have to enable the antenna power (AT+WANTGNSSPWR) but it does not work (ERROR replied). Unfortunately, AT+WANTS is not supported with my version of firmware, and the 06.xx.xx.xx firmware does not exist yet.

I have tried to modify the common variables with the AT!CUSTOM= command:
ISVOICEN (=> error)
GPSENABLE
GPSSEL
but the fix failed again.

I have also tried with AT!GPSCLRASSIST=1,1,1,1,1 without success.

The AT!GPSSATINFO? returns NO_SAT_INFO

AT!PCINFO?
State: Online
LPM force flags - W_DISABLE:0, User:0, Temp:0, Volt:0, BIOS:0, GOBIIM:0
W_DISABLE: 0
Poweroff mode: 0
LPM Persistent: 0
OK

AT!HWID?
Revision: 1.1
OK

AT!GVER?
!GVER: SWI9X15C_05.05.58.00 r27038 carmd-fwbuild1 2015/03/04 21:30:23
OK

AT!CUSTOM?
!CUSTOM:
PCSCDISABLE 0x03
GPSENABLE 0x01
GPSLPM 0x01
RRCREL7CAPDIS 0x02
NMEAENABLE 0x01
GOBIIMEN 0x01
SINGLEAPNSWITCH 0x01
USBSERIALENABLE 0x02
OK

AT!ERR
QDSP6 ARM9 (not saved)
00 96 ecall_e 00315
01 85 uim 12788
02 01 nvim 00740
03 02 nvarchi 00211
04 01 atsd 03377
05 96 stm 00512
06 03 rrccspd 01035
07 96 mc 05725
08 96 hdrscp 07855
09 96 hdrscmd 04824
10 96 hdrscmr 00647
11 96 hdrlmac 00760
12 96 hdrlmac 00770
13 96 hdrlmac 00782
14 96 gmmutil 01114
15 96 hdrlmac 00811
16 96 gmmutil 01147
17 FF cmnv 00792
18 96 hdridle 00800
19 02 mc_fee 01963
OK

I am not completely sure my antenna is plugged on the right antenna output (GPS named output, I suppose it is related to GPSSEL setting).
Is the PIN code mandatory when using GPS feature only?
Is the password for AAT commands always the same on the MC/EM series? I have been searching for a long time on the web in order to find it.

Thank you for your help.

Best regards.

Frederic

Update : I came accross an application note about GPS active antenna supply (2174027-1.0) and I noticed that the 3.3V power supply was not provided by the module to my antenna. However, the GPSSEL variable is set to 0 which should enable the GPS antenna supply according to this application note.

2

Any mistake in the way I proceed to make the GPS work? Thank you.

3

I suggest you take a look at the application notes regarding active antennas for GPS:

http://source.sierrawireless.com/resources/airprime/application_notes_and_code_samples/airprime-gps_active_antenna_supply/

4

Thank you krima919. I have already seen this application note (see my update in the first post).

5

In your case I assume your two antennae are the main and diversity ones. This means the 3rd antenna connector for GPS is open. Then you need to issue at!entercnd=“A710”

at!custom=“gpssel”,1

also you need to set up the gpssuplurl to supl.google.com. at!gpsportid to 7275 or 7276. at!gpstranssec can be used to disable the transport security so you won’t run into SSL problems. In addition you want to do an MS-Based fix otherwise it will take 10 minutes to get a fix. Also at!gpsxtradataenable and the related settings if you wish to use gpsonextra. I have gps working well now on my mc7355 but it is an ordeal to get all the settings right. I have been able to get the GPS assistance to work on AT&T, T-Mobile and Sprint networks.

As an aside I still wonder why modern equipment takes so long to get a fix without assistance when my old Bluetooth GPS receiver GNS 5870 from 7 years ago gets it so fast without any type of A-GPS/GPSOneXtra.

Best thing is to download the MC/EM73xx AT command reference and go to the GPS section and set all the appropriate settings.

6

Thanks for your answer guho but it does not work.

What firmware do you use?
What antenna do you use (passive or active)?

7

Currently running sprint SWI9x15C_05.05.63.01 r 28860 firmware on my mc7355.

Antenna is WWAN passive antenna built in notebook. There are only 2 WWAN antennas in my notebook so I do not have a dedicated GPS antenna. So the diversity antenna receives GPS signals with GPSSEL=1.

In skylight, set to MS Based. If it is greyed out you have to download an old version of skylight (it was called aircard watcher). I have reported a number of times that the MS Based selection was greyed out on the latest skylight but that report has been ignored by the Sierra Wireless employees on this forum.