Several errors wthen subscribing to two topics

asked 2017-01-26 13:11:01 -0500

zfellone
26 ●1 ●1 ●3

updated 2017-01-26 13:33:41 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

When I subscribe to one topic everything works perfectly but when I try to subscribe to two topics I get a variety of errors

[INFO] [1485455415.530806]: ROS Serial Python Node
init done
[INFO] [1485455415.598943]: Connecting to /dev/ttyACM0 at 57600 baud
[INFO] [1485455415.730069]: ROS Serial Python Node
[INFO] [1485455415.759043]: Connecting to /dev/ttyACM0 at 57600 baud
[INFO] [1485455417.851490]: Note: subscribe buffer size is 512 bytes
[INFO] [1485455417.851787]: Setup subscriber on external1/tag_pose [apriltags_ros/MetaPose]
[INFO] [1485455417.862592]: Setup subscriber on external2/tag_pose [apriltags_ros/MetaPose]
[INFO] [1485455417.974516]: Note: subscribe buffer size is 512 bytes
[INFO] [1485455417.974869]: Setup subscriber on external1/tag_pose [apriltags_ros/MetaPose]
[INFO] [1485455430.471515]: wrong checksum for topic id and msg
[ERROR] [1485455432.946574]: Lost sync with device, restarting...
[INFO] [1485455432.993689]: wrong checksum for topic id and msg
[INFO] [1485455435.496778]: wrong checksum for msg length, length -2304
[INFO] [1485455435.502251]: chk is 10
[ERROR] [1485455447.947238]: Lost sync with device, restarting...
[WARN] [1485455453.022465]: Serial Port read failure: object of type 'int' has no len()
[INFO] [1485455453.028041]: Packet Failed :  Failed to read msg data
[INFO] [1485455453.028446]: msg len is 8
[INFO] [1485455458.150668]: wrong checksum for topic id and msg
[INFO] [1485455493.152246]: wrong checksum for topic id and msg
[ERROR] [1485455493.157915]: Lost sync with device, restarting...
[INFO] [1485455493.291012]: Setup subscriber on external2/tag_pose [apriltags_ros/MetaPose]
[WARN] [1485455500.782483]: Serial Port read failure: device reports readiness to read but returned no data (device disconnected or multiple access on port?)
[INFO] [1485455538.406165]: wrong checksum for topic id and msg
[INFO] [1485455558.412407]: wrong checksum for msg length, length -257
[INFO] [1485455558.412790]: chk is 8
[ERROR] [1485455580.912865]: Mismatched protocol version in packet: lost sync or rosserial_python is from different ros release than the rosserial client
[INFO] [1485455580.913300]: Protocol version of client is unrecognized, expected Rev 1 (rosserial 0.5+)

For reference I have two callback functions(messageCb1 and messageCb2) and two different subscribers(ex1 and ex2). Both subscribers subscribe to the same message type but each is from a different topic. The message type is a custom message with a Pose and two floats.

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answered 2017-01-27 08:44:14 -0500

zfellone
26 ●1 ●1 ●3

My problem was trying to run two serial nodes in launch. Fixed and works wonderfully.

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answered 2017-01-26 14:53:38 -0500

Steven_Daniluk

606 ●2 ●7 ●14

My first thought is that you are trying to send too much data over serial. You mention that the messages that you are receiving contain a pose and two floats. That means they are (7*64 + 32 + 32) bits per message. This gives ~512 bits per message, and you are subscribing to two topics containing these messages.

If you are using the default baud rate of 9600, you will likely have issues. If both of your topics were publishing at 20Hz, that would result in 20,480 bits/s (202512). Plus there should be a bit of overhead for communication on top of that.

Also, I believe rosserial_arduino's buffer is about 80 bytes (I read that somewhere, but I cannot recall where). Two of your messages consume 128 bytes, which would be problematic if my memory of an 80 byte buffer is correct.

So, your options then would be:

Increase the baud rate, and hope the buffer is not the limiting factor
Find a way to reduce your message size (do you need all 6 degrees of freedom in the pose?)
Throttle the frequency which your messages are published (can whatever your messages are being used for respond at that rate?)

You can increase the baud rate with the arduino by adding to your arduino script:

nh.getHardware()->setBaud(57600);

Along with the parameter for the rosserial_arduino node:

<param name="baud" value="57600"/>

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I'll look into increasing the baud rate. I am already using a baud rate of 57600.

zfellone ( 2017-01-26 15:15:08 -0500 )edit

Ah, I missed that from your log output, sorry. I also missed that it states the subscriber buffer size as 512 bytes. Would you be calling spin() on the arduino close to how frequently the messages are being published? Just to avoid messages piling up.