blimb
January 17, 2025, 1:47pm
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!
jyijyi
January 17, 2025, 1:59pm
2
You need to enter the following
At!gpsend=0
At!gpsfix=1,255,100000
blimb
January 17, 2025, 2:14pm
3
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?
jyijyi
January 17, 2025, 2:17pm
4
Are you testing in linux?
If so, do you open the correct nmea port to check?
blimb
January 17, 2025, 2:21pm
5
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#
jyijyi
January 17, 2025, 2:23pm
6
Then did you see the nmea port like /dev/ttyUSB1 ?
blimb
January 17, 2025, 2:36pm
7
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.
jyijyi
January 17, 2025, 2:38pm
8
Uart is only for AT command, not for nmea frame
blimb
January 17, 2025, 2:44pm
9
Ah ok. Is the NMEA frame send using USB?
blimb
January 17, 2025, 2:48pm
11
That cleared up a lot. Thanks for the help!
blimb
January 23, 2025, 12:21pm
12
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?
jyijyi
January 23, 2025, 3:07pm
13
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.
1 Like
blimb
January 24, 2025, 8:37am
14
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?
jyijyi
January 24, 2025, 9:12am
15
you need to use USB to have AT command communication
Once UART is set to NMEA service, it cannot accept AT command
blimb
January 24, 2025, 9:13am
16
Ah so that’s the tradeoff. All clear, thanks!
blimb
January 24, 2025, 2:06pm
17
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.