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Able to subscribe to topic but no output

asked 2020-09-14 10:06:49 -0600

Mackou gravatar image

updated 2022-08-07 08:53:07 -0600

lucasw gravatar image

Hello everyone, I have a very weird problem while subscribing to a topic.

I have a bagfile containing this specific topic :

/radar_fc/parsed_tx/radartrack                                  395180 msgs    : delphi_esr_msgs/EsrTrack

It contains messages, so it looks fine.

But when I play the bag and subscribe or try to echo the topic, I get nothing. No error message, no error, nothing !

rostopic echo /radar_fc/parsed_tx/radartrack

rostopic info /radar_fc/parsed_tx/radartrack tells me that I subscribe to it correctly :

Type: delphi_esr_msgs/EsrTrack

 * /play_1600094136880686877 (http://max-XPS:34781/)

 * /rostopic_8207_1600094360816 (http://max-XPS:40245/)

When I try rostopic hz I get an output :

rostopic hz /radar_fc/parsed_tx/radartrack
subscribed to [/radar_fc/parsed_tx/radartrack]
average rate: 1205.332
    min: 0.000s max: 0.059s std dev: 0.00480s window: 1144
average rate: 1200.979
    min: 0.000s max: 0.059s std dev: 0.00483s window: 2342
average rate: 1218.411
    min: 0.000s max: 0.059s std dev: 0.00475s window: 3597
average rate: 1227.879
    min: 0.000s max: 0.059s std dev: 0.00473s window: 3999

First I though that the message was not installed or compiled but when I do rosmsg info delphi_esr_msgs/EsrTrack to get the message information everything is correct :

rosmsg info delphi_esr_msgs/EsrTrack        
std_msgs/Header header
  uint32 seq
  time stamp
  string frame_id
string canmsg
uint8 track_id
float32 track_lat_rate
bool track_group_changed
uint8 track_status
float32 track_angle
float32 track_range
bool track_bridge_object
bool track_rolling_count
float32 track_width
float32 track_range_accel
uint8 track_med_range_mode
float32 track_range_rate

roswtf tells me there is an error but I don't understand where it comes from :

Found 1 error(s).

ERROR The following nodes should be connected but aren't:
 * /play_1600094136880686877->/rostopic_8207_1600094360816 (/radar_fc/parsed_tx/radartrack)

Do you have any idea what could be the problem ?

Thanks !

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I have to rostopic echo after starting the starting bagfile? Are you using sim time while playing file. Is it possible echo is looking for current messages and bagfile playing old messages? <-- just a thought, I don't have any experience with bagfiles.

billy gravatar image billy  ( 2020-09-14 20:33:04 -0600 )edit

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answered 2020-09-15 07:09:53 -0600

Mackou gravatar image

Updating ROS solved the issue

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Asked: 2020-09-14 10:06:49 -0600

Seen: 164 times

Last updated: Sep 15 '20