Leveraging GPS in MC7700

[Adam Sherman]

On 2017-02-06 07:42 AM, Aleksander Morgado wrote:
>>>>> No, there is a way to do that, enabling the GPS receiver with AT
>>>>> commands and processing the NMEA traces received from another TTY; it
>>>>> just isn't implemented in ModemManager. We could implement the
>>>>> "unmanaged gps" location support in the Sierra plugin to handle that
>>>>> usecase.
>>>> If I need to use the GPS in this card right now, what does that look like?
>>> For a quick hack, you could blacklist all tty ports exposed by the
>>> modem with MM_PORT_IGNORE flags in udev rules, and then do the AT
>>> commands to start/stop GPS yourself. This would leave the modem
>>> running in QMI mode through ModemManager and you would be able to use
>>> the ttys as you wish at the same time.
>> And none of those ttys are required for the network data?
> None of them,no. When running in QMI mode just the cdc-wdm port and
> the wwan network interface are required to manage the modem.

Output of mmcli shows ports: 'ttyUSB0 (qcdm), ttyUSB2 (at), cdc-wdm0
(qmi), wwp0s20u4i8 (net)'.

Does that mean it ttyUSB1 is the serial GPS strings port?

I found the example[1] you provided in comments on your blob, actually
directed at me, which I didn't compute until going through all of this,
sorry about that. So I think I will try the following:

$ cat /etc/udev/rules.d/77-mm-MC7700-ignore-TTYs.rules
ATTRS{idVendor}=="0f3d", ATTRS{idProduct}=="68a2", SUBSYSTEM=="tty",
ENV{ID_MM_PORT_IGNORE}="1"

Then I should issue the AT commands to ttyUSB2. Going to test this right
away.

Thanks,

A.

[1]:
https://sigquit.wordpress.com/2012/03/29/enabling-gps-location-in-modemmanager/#comment-7138

-- 
Adam Sherman <adam at sherman.ca>