How to get a NMEA sentence using RC7620-1

Hello!

I have been using the RC7620-1 that is connected to a MCU and using Zephyr to communicate with it. Currently I am trying to retrieve a NMEA sentence, but I do not understand how to do this.

I am able to acquire a fix using:

AT!GNSSCONFIG=1,1,1,1,1
AT!GPSAUTOSTART=1,1,60,4294967280,10
AT!GPSSTATUS?
AT!GPSLOC?

I tried adding the following AT commands, but that did not seem to change anything.

AT!GPSNMEASENTENCE=3
AT!GPSNMEACONFIG=1,10

I seem to be misunderstanding or missing something. Any insight is greatly appreciated!

You need to enter the following

At!gpsend=0
At!gpsfix=1,255,100000

Thanks for the reply!

I initially used GPSFIX but back then I received NO CARRIER, but it seems fine now?

After adding the commands to my other commands, I sadly cannot see any NMEA sentences. It might be on my end then?

Are you testing in linux?
If so, do you open the correct nmea port to check?

I am using Zephyr RTOS with the Modem driver. And communicating to the Modem using CMUX and PPP

AT+CMUX=0,0,5,127
ATD*99***1#

Then did you see the nmea port like /dev/ttyUSB1 ?

Sorry I actually have no clue how I should be looking for it currently.

I am connected to a MCU that is connected to the modem. In the Device Tree within Zephyr I mapped the pins, so that I can communicate to it using UART. The only port that I am able to see on my workstation is the one connected to the MCU.

Uart is only for AT command, not for nmea frame

Ah ok. Is the NMEA frame send using USB?

Yes, that is correct

That cleared up a lot. Thanks for the help!

Sorry 1 more question.

I was fiddling around with DLCI and noticed that NMEA sentences are send through the 3rd channel when it has not yet found a fix.

Also the RC76xx firmware release 10.0 mentions the following:

USB NMEA format data can now be transmitted through the UART interface.

I could not find documentation regarding it, so it is not completely supported yet I guess?

I just found that you can set NMEA service with UART with AT!MAPUART=4,1 with FW R10

So I believe NMEA format data can now be transmitted through the UART interface in FW R10.

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Yes that seemed to work thanks!

Got a slightly new issue though. It sends out so many NMEA sentences that I kind of locked myself from sending any new AT commands. Any suggestion on how to solve this problem? :sweat_smile:

you need to use USB to have AT command communication

Once UART is set to NMEA service, it cannot accept AT command

Ah so that’s the tradeoff. All clear, thanks!

Another way is listening to DLCI 3. Seems like it returns NMEA sentences as well. So I am able to send AT commands and acquire NMEA sentences on UART.