MicroNav USBL GPS on a BR2

Type this command in the terminal window:

screen -r nmearx

position seems to be going into the PI, am i correct ?

Data is getting to the Pi,. But it looks like there’s an issue with the NMEA stream
Is it in this format:

The error in the terminal indicates a checksum issue

i re ran it again and got this

I think that’s a Linux thing. My weak point. I think if you hit ctrl-x and exit, then open the window again. It should work.


the first screen -r nmearx was with $GPGGA

and then i changed it to $GPRMC to see if it made any difference ,

i was advised to use the GPGGA data format to send the transponder position by tritech

my NMEA router settings


$GPRMC data format going through my router


It looks like the checksum is not right?

I’m used to seeing something like “A*43” as a checksum format. not just “*73” like you have.

Hopefully someone else in this forum can advise…NMEA_ROV

HI thanks for all your help and assistance , i hope that maybe the BR technician will be able to advise me on the correct setting tomorrow when they get back to work


@Mac1 can you paste some lines in this online NMEA checksum tester to verify the checksums?

hello william,
I opened the online check sum calculator page , but cannot see how it runs , what do i click on to see the data ,what lines do i paste ?
sorry for not understanding

just pasting the line in the text field and pressing enter/tab.


The checksum does look wrong (or perhaps I wrote something wrong, and I typed that in manually).

Hi i pasted the line from the NMEA router into the checksum


and this was the checksum reading after hitting enter

the checksum here is the *7A,
so you should paste GPRMC,153611.11,A,3557.61860,N,01422.33320,E,0.00,000.00,040121,
and it will show the whole NMEA sentence (with calculated checksum) at the bottom.

that was the checksum reply after hitting enter

Command: $
With checksum: $GPRMC,153611.11,A,3557.61860,N,01422.33320,E,0.00,000.00,040121,*11

These are my data output option formats on my micronav

I would like to thank the Blue Robotics team and the people on this forum for all their help and assistance in working towards and fixing my transponder position reading on the QGC, in the end it was resolved by Blue Robotics technician Willian Galvni who set up a remote access and fixed the problem.
Thanks you all and keep up the good BR products

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Nice you had a solution in the end!
What was the problem, for the knowledge base?

it turned out that it was a check sum issue , Willian managed sorted the program out , it was a problem with the Tritech genesis program

Willian contacted Tritech and they updated the program,

Reply from Tritech :
The coding in Genesis skips the first character in the checksum generation but the string being sent to the function has the $ already removed.

Thank you for making us aware of this and a fix has already been implemented. This fix will definitely be rolled out in V1.7 of Genesis