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nmea_navsat_driver /fix topic hangs indefinitely

asked 2018-04-30 13:02:12 -0600

popenc gravatar image

Hey everyone!

I'm running into an issue that I've previously resolved and have seen posted in a few different places, so apologies if it's a duplicate. This weekend, I started getting this problem again where I run the nmea navsat driver ROS package to read in GPS strings via USB, and can see the serial messages via "$ cat /dev/<device>", but when I try to echo the "/fix" topic it just hangs.

Goal: Have the robot read GPS data via USB from a GPS unit.


  • OS - Ubuntu 14.04
  • More OS info - Linux CPR-J100-0057 3.16.0-77-generic #99~14.04.1-Ubuntu SMP Tue Jun 28 19:17:10 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
  • ROS - Indigo 1.11.20
  • GPS Package - nmea_navsat_driver 0.4.2
  • GPS unit - Emlid Reach RS, ReachView app 2.11


  • With the robot powered on, the ROS core is started with the following env vars using the robot's IP address:

    export ROS_MASTER_URI=

    export ROS_IP=

  • GPS device is plugged into the robot's USB port, I see the device shows up in /dev:

    ls /dev/ttyA*

    Listed devices: /dev/ttyACM0 /dev/ttyACM1

  • I'm able to display the serial data coming into the robot:

    cat /dev/ttyACM1

    Example printout:

    $GPGSA,A,3,07,08,09,11,23,48,51,,,,,,3.1,1.7,2.6*3D $GLGSA,A,3,67,68,77,78,88,,,,,,,,15.2,4.7,14.4*2A $GPGSV,2,1,07,07,44,322,48,08,79,128,45,09,55,248,45,11,27,170,37,1*65 $GPGSV,2,2,07,23,39,190,42,48,26,246,37,51,45,220,43,,,,,1*58 $GLGSV,2,1,05,67,22,239,41,68,22,296,44,77,49,019,38,78,27,317,38,1*7B $GLGSV,2,2,05,88,36,166,37,,,,,,,,,,,,,1*4D $GNGST,173725.20,1.220,,,,4.514,4.529,10.741*5C $GNVTG,,T,,M,0.09,N,0.17,K,A*32 $GNRMC,173725.40,A,3128.5281612,N,08331.7091448,W,0.04,,300418,,,A*4A $GNGGA,173725.40,3128.5281612,N,08331.7091448,W,1,12,0.0,108.391,M,-28.500,M,0.0,*61

  • Next, I try running the nmea navsat driver ROS package and match the GPS settings for port and baud rate. It seems like these settings being wrong is a classic way for this not to work, but given step 3 above, it seems like that isn't the issue here.

    rosrun nmea_navsat_driver nmea_serial_driver _port:=/dev/ttyACM1 _baud:=4800

    NOTE: I get this warning when I run the package, but I think it's only temporary at startup. I've had this same warning a week ago when everything was working. The warning:

    [WARN] [WallTime: 1525110076.762267] Received a sentence with an invalid checksum. Sentence was: '$GPGSV,2,1,08,07,45,323,43,08,80,117,46 ...

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1 Answer

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answered 2018-05-02 07:35:39 -0600

popenc gravatar image

For my particular situation, this doesn't seem like a ROS issue and ended up being an issue on the Emlid Reach RS GPS unit side.

As I mentioned in the OP, the problem described in this post didn't happen until after updating the GPS unit's control/monitoring software, ReachView. Given that I was able to verify the serial data (i.e., GPS strings) coming into the robot, I really didn't expect the GPS software update to be a factor in the issue at all. The only reason I was suspicious of the upgrade causing any issues was that it was the only thing changed between it working and not working.

When I downgraded my ReachView app version from 2.11 back to 2.10, and ran the same setup described above, I get the /fix and /vel topics echoing again.

I'd like to attempt to recreate this exact same behavior before fully committing to the idea that the ReachView upgrade caused an odd bug with ROS, the NMEA driver, or something along the chain.

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The command stty -F /dev/ttyACM1 may help you troubleshoot. I used it when I had a problem with a ROS node and serial port configuration. I had a serial-to-USB adapter, so I used stty -F /dev/ttyUSB0 to see the working and non-working configurations and find the difference.

tryan gravatar image tryan  ( 2018-09-15 09:31:44 -0600 )edit

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Asked: 2018-04-30 13:02:12 -0600

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Last updated: May 02 '18