MC7710 GPS no signal no sat info at all


#1

Hi everyone,

I have an MC7710 AirPrime device and my goal is only to get GPS information.

  • I’m using Debian 8 and my device firmware version is as follows: SWI9200X_03.05.19.04ap r5475 carmd-en-10527 2012/09/17 17:57:14
  • Issuing AT commands on ttyUSB2 and reading NMEA ouput on ttyUSB1.
  • MAIN and GPS antennae are connected to passive antennae.

Custom config is as follows:

!CUSTOM: 

        PUKPRMPT		0x01
        MEPCODE		0x01
        ISVOICEN		0x02
        PRLREGION		0x01
        PCSCDISABLE		0x03
        GPSENABLE		0x04

I’ve been trying hard for 2 days, but it seems like the MC7710 gets no signal at all:
printf ‘AT!GPSSATINFO?\r’ > /dev/ttyUSB2
NO SAT INFO

I’ve verified with my phone and GPS signal seems OK, 6 sats at 20-30 dB of SNR.

printf 'AT!GPSSTATUS?\r' > /dev/ttyUSB2
Current time: 2015 08 26 2 12:31:21

    2015 08 26 2 12:30:49 Last Fix Status    = FAIL,  FAILCODE = 12

    1980 01 06 6 00:00:00 Fix Session Status = ACTIVE

No TTFF available

Date and time are terribly wrong, but I don’t know how to set it. I live in Argentina and my date and time were 2018-08-24 16:45

I executed the diagnostic procedure shown in the tech specs and I get :
CtoN=0.0 Freq=0

ttyUSB1 outputs constantly as follows:

$GPRMC,,V,,,,,,,,,,N*53
$GNGNS,,,,,,NN,,,,,,*53
$GPVTG,,T,,M,,N,,K,N*2C
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GNGSA,A,1,,,,,,,,,,,,,,,*00
$GPGGA,,,,,,0,,,,,,,,*66
$GNGNS,,,,,,NN,,,,,,*53
$GNGNS,,,,,,NN,,,,,,*53
*78

I really have no idea what can be done. Can anyone shed some light?

Regards,


#2

Try connect your GPS antenna to the dedicated GPS port with a blue triangle indicator.


#3

Thanks for your reply. That’s what I’m doing, I mistyped… “MAIN and GPS antennae ports are connected to passive antennae”.

I’m using regular router 20cm antenna as passive GPS antenna.


#4

Just a newbie question… I don’t have a SIM card connected to my computer, could this be a problem? Or is the GPS module completely independent?


#5

You don’t need a SIM to get the GPS working but you do need a GPS antenna to get good reception. A router antenna may not be designed to receive GPS signal. You’d better try a antenna that supports GPS.


#6

The antenna is ok since the signal’s wavelength is suitable for the anntenna’s length. Nevertheless, I’m buying an active GPS antenna to give it a try.

Another thing I’d like to stress: my MC7710’s date and time are very wrong, how can I correct this?


#7

If you are sure the GPS antenna is okay then connecting it to the aux port and issuing the following AT commands and see how it goes before getting the active antenna. Make sure you are in clear view to the sky though.
AT!CUSTOM=“GPSSEL”,01
AT!RESET

Also for active GPS antenna to work, you need to connect to the dedicated GPS port.


#8

From my experience pretty much all of these issues are down to getting a working antenna, after that it just fires up.

You also might want to look at this.

2170045 - SWI Application Note - SL8 and Mini card GPS operation.docx (245.1 KB)

Regards

Matt