Problems to get valid location data with Sierra Wireless MC7455

Ulrich Ölmann u.oelmann at
Fri Sep 21 10:02:24 UTC 2018

Hi Aleksander,

Aleksander Morgado <aleksander at> writes:
>> [...]
>> While just pasting ModemManager's log for the first time I stumbled
>> across the second warning ("Could not grab port (tty/ttyUSB1): 'Cannot
>> add port 'tty/ttyUSB1', unhandled serial type'"), and presumably this is
>> the reason for not getting any location data as /dev/ttyUSB1 seems to be
>> the source for GNSS information, right? So what am I doing wrong here?
> That is not the issue, no. ttyUSB1 may be unhandled, because you're
> really receiving all location information via QMI LOC service. If you
> run MM in debug mode (with --debug) then you should see all QMI LOC
> messages being reported every 1s with the NMEA traces reported by the
> modem. You can see those NMEA traces in mmcli output (e.g. GPGGA...)
> but the module isn't returning any location yet.

in fact I repeatedly see many many lines a'la

    [/dev/cdc-wdm0] received message...
    [/dev/cdc-wdm0] received generic indication (translated)...
    <<<<<< TLV:
    <<<<<<   type       = "NMEA String" (0x01)
    <<<<<<   length     = 26
    <<<<<<   value      = 24:47:50:47:47:41:2C:2C:2C:2C:2C:2C:30:2C:2C:2C:2C:2C:2C:2C:2C:2A:36:36:0D:0A
    <<<<<<   translated = $GPGGA,,,,,,0,,,,,,,,*66
    <debug> [1517443403.601456] [NMEA] $GPGGA,,,,,,0,,,,,,,,*66

which is found in the NMEA traces of the mmcli output as well - so it
looks like the data steadily sent by the MC7455 contain always the same
message of invalid location data and at least the software side can be
regarded as being okay.

>> Then there are additional QMI related warnings ending with "No valid
>> firmware images listed. Assuming firmware unsupported." - could it be
>> that they are somehow related? Do I have to flash a more current
>> firmware?
> Nah, don't think those are related.


>> If this looks familiar to somebody I would be very glad to get a hint
>> where to look deeper.
> I assume that given that you don't have network connection, A-GPS may
> not work at all, so you're really running with standalone GPS. [...]

I have the board in our lab where it is connected to the internet via
LAN, so I manually downloaded the data for assisted GPS and sent it up
to the modem

    root at MP:~ wget
    --2018-09-21 11:33:49--
    Resolving (,,, ...
    Connecting to (||:80... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: 29150 (28K) [application/octet-stream]
    Saving to: ‘xtra3grc.bin.6’

    xtra3grc.bin.6          100%[==============================>]  28.47K  --.-KB/s    in 0s

    2018-09-21 11:33:49 (324 MB/s) - ‘xtra3grc.bin.6’ saved [29150/29150]

    root at MP:~ mmcli -m 0 --location-inject-assistance-data=xtra3grc.bin
    successfully injected assistance data

Waiting for 15 minutes I still get no valid location

    root at MP:~ mmcli -m 0 --location-get

      3GPP location   | Not available
      GPS NMEA traces | $GPGGA,,,,,,0,,,,,,,,*66
                      | $GPGSA,A,1,,,,,,,,,,,,,,,*1E
                      | $GPVTG,,T,,M,,N,,K,N*2C
                      | $GPRMC,,V,,,,,,,,,,N*53
      Raw GPS         | Not available
      CDMA BS         | Not available

> [...] Do you have the GPS specific antenna connected to the module? Do
> you have good satellite coverage?

The GPS specific antenna is connected to the module and hopefully the
satellite coverage is sufficient (my mobile phone tells me that it sees
10/27 satellites if it is held next to the GPS antenna). So I assume
that perhaps there is some technical problem with respect to the antenna
which should be excluded before further suspecting the software setup.

Have my big thanks for helping! :-D
(At least I hopefully can give a little bit back as I stumbled across a
small thing in the code that I am going to send a patch for right now).

Best regards
Pengutronix e.K.                           | Ulrich Ölmann               |
Industrial Linux Solutions                 |  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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