Serial LTE Modem + GPS

RE: Serial LTE Modem + GPS

Håkon Alseth — Wed, 15 Mar 2023 08:51:15 GMT

Hi,

If we take the GPGSV from just before a fix is produced (lines 3231-3232):

2023-03-14T16:11:27.636Z DEBUG modem << $GPGSV,2,1,5,7,,,30,8,,,28,9,,,27,27,,,28,1*67
2023-03-14T16:11:27.641Z DEBUG modem << $GPGSV,2,2,5,30,,,27,1*57

Here you have 5 satellites with SNR of 30, 28, 27, 28, and 27.

This is the CN0 (in dB/Hz), which is a number that you want to be >30 to ensure a good reception.

This was from the DK, right? If you get the fanstel module logging these NMEA strings in the exact same position as you tested just now, we can compare the GPGSV strings between the two to see if there's an antenna performance difference.

Kind regards,

Håkon

RE: Serial LTE Modem + GPS

jhadella — Tue, 14 Mar 2023 23:05:38 GMT

I was able to collect some data using that project on the DK board. See attached.

I was having trouble getting the same on the Fanstel board. I normally use my custom nrf52840 usb uart passthrough app, but the frequency of the NMEA was causing issue. The nrf connect app doesn't seem to work correctly with that hardware. I'm using another dk with jtag.

devzone.nordicsemi.com/.../nrf9160_5F00_dk_5F00_gnss_5F00_log.txt

RE: Serial LTE Modem + GPS

Håkon Alseth — Fri, 10 Mar 2023 13:41:18 GMT

Hi,

Thanks for posting the pictures. This helps alot.

[quote user="jhadella"]

Tested again today with no other changes. This time, I mounted the Fanstel device to the roof of my car. It eventually worked! Seems like after enabling it took 10-15 to lock. Tested with and without LTE.

Interestingly, the last test I did had LTE enabled. Not sure if coincidence or not, but after 10 minutes or so it didn't seem like it was working then I did a "AT%XMAGPIO?" and it immediately started pumping out GPS data.

I need to automate this stuff for use in our device. Let me know if that weird polling for the xmagpio is sensible. Could just be a fluke it started right after?

[/quote]

Good to hear that you got a fix. I think there is a performance gap between the two designs here.

If you run the gnss sample (and set CONFIG_GNSS_SAMPLE_NMEA_ONLY=y), you should be able to get NMEA strings out directly from each module. Here, I'm interested in the CN0 for each respective satellite. This is a number that you want to be >30 for atleast 4 satellites in order to produce a fix.

Could you try this and share the log for both DK and your custom board?

Kind regards,

Håkon

RE: Serial LTE Modem + GPS

jhadella — Thu, 09 Mar 2023 23:21:06 GMT

I need to automate this stuff for use in our device. Let me know if that weird polling for the xmagpio is sensible. Could just be a fluke it started right after?

RE: Serial LTE Modem + GPS

jhadella — Thu, 09 Mar 2023 17:00:47 GMT

I've been testing the DK board and the module labeled BLN60E-B840-V6.

On the Nordic side, I'm using the LTE Link Monitor. On the module, the nRF52840 is a running some firmware I wrote which allows me to write AT commands via USB which are rerouted to the nRF9160 over UART, and then the UART responses are written back over USB. It functions almost the same as the LTE Link Monitor but is simpler.

The module's connector under the label is for LTE -- this is just a pic of a loose board.

RE: Serial LTE Modem + GPS

Håkon Alseth — Thu, 09 Mar 2023 14:41:42 GMT

Hi,

Can you share pictures of the module that you're using?

Kind regards,

Håkon