nothing show when I run rostopic echo /nmea_sentence

asked 2020-11-09 03:17:06 -0500

huanghehe
1 ●1 ●1 ●1

updated 2020-11-10 08:50:16 -0500

Hi, I played a utbm_robocar rosbag with "rosbag play utbm_robocar_dataset_20190418_noimage.bag" ,which contains NMEA messages (nmea_msgs/Sentence),it run well.

then I run rostopic list , there show:

/clock
/cloud
/hdl32e_left/velodyne_packets
/imu/data
/imu/mag
/imu_data_str
/nmea_sentence
/objects
/received_messages
/rosout
/rosout_agg
/scan
/velocity

Then I run `rostopic echo /nmea_sentence, nothing show in the terminal,why?

I had installed ros-melodic-nmea-msg

Any, idea of what is going on?

I checked rostopic echo /imu/data or rostopic echo /scan, it show correctly

I checked rostopic info /nmea_sentence, it show

Type: nmea_msgs/Sentence

Publishers: 
  * /play_1604911497764697838 (http://huanghehe:44631/)

Subscribers: None

Thanks in advance

Hi, I played a utbm_robocar rosbag with "rosbag play utbm_robocar_dataset_20190418_noimage.bag" ,which contains NMEA messages (nmea_msgs/Sentence),it run well.

then I run rostopic list , there show:

/clock
/cloud
/hdl32e_left/velodyne_packets
/imu/data
/imu/mag
/imu_data_str
/nmea_sentence
/objects
/received_messages
/rosout
/rosout_agg
/scan
/velocity

Then I run `rostopic echo /nmea_sentence, nothing show in the terminal,why?

I had installed ros-melodic-nmea-msg

Any, idea of what is going on?

I checked rostopic echo /imu/data or rostopic echo /scan, it show correctly

I checked rostopic info /nmea_sentence, it show

Type: nmea_msgs/Sentence

Publishers: 
  * /play_1604911497764697838 (http://huanghehe:44631/)

Subscribers: None

Thanks in advance

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Comments

Could you please run rosbag info utbm_robocar_dataset_20190418_noimage.bag and post the results? You might notice something.

miura ( 2020-11-09 09:42:20 -0500 )edit

'rosbag info utbm_robocar_dataset_20190418_noimage.bag'

topics:

  /cloud                            11198 msgs    : sensor_msgs/PointCloud2       
  /imu/data                         89575 msgs    : sensor_msgs/Imu            
  /imu/mag                          89575 msgs    : sensor_msgs/MagneticField  
  /imu_data_str                     89575 msgs    : std_msgs/String            
  /nmea_sentence                    13435 msgs    : nmea_msgs/Sentence         
  /objects                          11193 msgs    : sick_ldmrs_msgs/ObjectArray
  /received_messages              2695753 msgs    : can_msgs/Frame             
  /scan                             44609 msgs    : sensor_msgs/LaserScan

as you said. sorry, I run rostopic info /nmea_sentence can see everything, but I run rostopic echo /nmea_sentence can't see anything. I made a mistake about the question.

huanghehe ( 2020-11-10 05:52:57 -0500 )edit

I suspect this has to do with nmea_sentence being of a custom message type. Can you try rosmsg show nmea_msgs/Sentence in the same terminal where the rostopic echo doesn't work? I could imagine that it will not work, because the message definitions are not loaded.

chfritz ( 2020-11-10 09:38:37 -0500 )edit

I also met this problem.Try play bag on another PC,can get the echo data.

wjh731 ( 2020-12-02 21:32:05 -0500 )edit

If bag file sharing was possible, I can try it on my PC.

miura ( 2020-12-06 05:45:47 -0500 )edit

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answered 2020-11-10 08:02:12 -0500

miura

1908 ●1 ●171 ●24 https://twitter.com/miura

I came up with one idea. It may contain special characters and clear the screen or something. You could try rostopic hz /nmea_sentence to check the communication cycle and rostopic echo /nmea_sentence > log_file to output to a text file and then look at the text file.

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I try rostopic hz /nmea_sentence and get information like this and it is updating:

subscribed to [/nmea_sentence]
average rate: 15.491
min: 0.000s max: 0.218s std dev: 0.08024s window: 15
average rate: 15.252
min: 0.000s max: 0.218s std dev: 0.07575s window: 30
average rate: 15.152
min: 0.000s max: 0.218s std dev: 0.07317s window: 45
average rate: 15.103
min: 0.000s max: 0.218s std dev: 0.07266s window: 60
...

But I tryrostopic echo /nmea_sentence > log_file and vim log_file,nothing show up, the file is empty

huanghehe ( 2020-11-10 08:47:13 -0500 )edit

Okay. I'm sorry, my prediction don't correct. I don't have any other ideas at the moment. If I come up with one, I'll comment on it.

miura ( 2020-11-11 05:08:02 -0500 )edit

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nothing show when I run rostopic echo /nmea_sentence

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