MicroNav USBL GPS on a BR2

ran ping commands on & 1
all happy and good replies

powered ROV off and on again (disconnected )
NMEA router working good
auto connect set to UDP and listen on 27000

transponder position still showing

Go back into the QGC Settings Parameters section;

Search: GPS_TYPE

I believe it should be set to: NMEA

set to NMEA now but no difference to transponder reading 000000

also on the Map screen it has always said “No GPS lock for the Vehicle”
i do not suppose that message gives you any extra info to work with as its more to do with the lat and long 00000 readings not changing

Log into the Raspberry Pi Terminal window, Run the ‘screen’ command and see if it’s happy.

I typed in screen and then enter and got a copy right result ?

is that correct ? for a happy result ?

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