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MAVLink to ROS gateway with proxy for Ground Control Station
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Send a new custom mavlink message from PX4 to mavros #682

Closed zhangyongwei93 closed 7 years ago

zhangyongwei93 commented 7 years ago

Hi,
I want to send a custom mavlink message to mavros, and transform to a ros topic form.
In pixhawk firmware (v1.5.2dev)

In mavros package (indigo-devel)

Current problem
I can read the custom mavlink message with the correct ID(220) and message LEN from serial port assistant in computer by connect the TELEM2 on PX4.
In mavros, after roslaunch mavros px4.launch,terminal outputed that the custom plugin has loaded and initialized.
But after rosrun mavros checkid,terminal outputed OK. I got messages from 1:1. Received 596 messages, from 1 addresses sys:comp list of messages 1:1 0, 65, 1, 230, 70, 33, 105, 74, 141, 111, 241, 242, 83, 147, 87, 36, 32, 30, 245 there is no message id with 220.

vooon commented 7 years ago

Did you recompile whole mavros? Known messages array compilled in libmavconn, and may be in other parts.

zhangyongwei93 commented 7 years ago

@vooon Sorry for replying late. I have recompiled whole mavros, and I tracked into the MAVConnSerial::async_read_end function in libmavconn/src/serial.cpp; at the mavlink message parse part mavlink_parse_char(channel, rx_buf[i], &message, &status), I found the function body in mavlink/v1.0/mavlink_helpers.h, and I confirmed it is the CRC error, then I disabled CRC just for test, the custom mavlink message really appeared. But why the CRC cause error?

vooon commented 7 years ago

Because each message at source gen stage generate additional byte computed from message definition. It is stored in message crc array and used by parse function. Note that msg crc do not send via wire, just added to packet CRC, so any unknown message will be reported as CRC error.

Mavros v0.18 do not process messages with errors, but passes trough /mavlink/from.

zyq1993 commented 7 years ago

hello,@zhangyongwei93

I have updated the /opt/ros/indigo/include/mavlink with mavlink folder in pixhawk firmware.

Can you tell me how to updated the directory /opt/ros/indigo/include/mavlink? I put my custom_messages.xml in mavros/src/mavlink/message_definitions, and rebuild, but there is no custom_messages in /opt/ros/indigo/include/mavlink/v1.0 and v2.0.

vooon commented 7 years ago

@zyq1993 that instruction for you: https://github.com/mavlink/mavros/blob/master/mavros/README.md#source-installation Do not forget to remove binary installed mavros and mavlink. Build result will be in workspace devel dir. Note that Kinetic version also works on Indigo, add --rosdistro=kinetic to all rosinstall_generator.

zyq1993 commented 7 years ago

Now，I have removed binary installed mavros and mavlink, and the mavlink directory in /opt/ros/indigo/include/ is removed too. After I rebuild the mavros package, there is still no mavlink directory in /opt/ros/indigo/include/. Dose it matter?

zyq1993 commented 7 years ago

If I need my custom_messages directory in /opt/ros/indigo/include/mavlink, what should I do?

vooon commented 7 years ago

Look at ~/catkin_ws/devel/include; Place your xml into ~/catkin_ws/src/mavlink/message_defenitions/v1.0

zyq1993 commented 7 years ago

I place the mavlink package and my custom_messages.xml into ~/catkin_ws/src, and do catkin build, I can find the generated headers in ~/catkin_ws/devel, but no mavlink directory in /opt/ros/indigo/include/. What should I do if I want there is a mavlink directory in the path /opt/ros/indigo/include/?

zhangyongwei93 commented 7 years ago

I think you can copy the generated mavlink directory in pixhawk firmware to the path /opt/ros/indigo/include/

zyq1993 commented 7 years ago

Oh, I solved it. Thanks a lot for the help of both of you! @vooon @zhangyongwei93

zyq1993 commented 7 years ago

Oh，I copied the generated mavlink directory to path /opt/ros/indigo/include/, but there is a new problem. I have a package, and that package needs generated mavlink header files, but I don't want to put the mavlink package into my package to compile together. I need a mavlink directory in /opt/ros/indigo/include/, so I don't need to put the mavlink package in my package. But the binary installed mavlink package dosen't contain my custom messages. Although I copied the mavlink package(contains custom messages) into /opt/ros/indigo/include/, but I can't use the copied mavlink headers in my code. It implied that there is no mavlink headers. How to solve my problem? Thanks a lot.

vooon commented 7 years ago

@zhangyongwei93 how thing going? Is that issue fixed?

@zyq1993 relying on particular directory is bad idea, you have cmake! And ros release provide config for build system. Also after build headers not heed anymore. And your package may build in same workspace as mavlink. To solve your task, i think (a bit dirty) solution is to make fork of release/kinetic/mavlink branch and commit here your dialect xml.

zhangyongwei93 commented 7 years ago

@vooon I modified the MAVLINK_MESSAGE_CRCS, and the issue has fixed. Thanks a lot.

zhangyongwei93 commented 7 years ago

@zyq1993 can you commit here your error message which implied that there is no mavlink headers?

zyq1993 commented 7 years ago

The mavlink msg id of my custom message is MAVLINK_MSG_ID_SENSOR_COMBINED_RAW, and when I compiles, the error is " 'MAVLINK_MSG_ID_SENSOR_COMBINED_RAW' was not declared in this scope". So，I gave up using headers in /opt/ros/indigo/include/ . I think only binary installed package can put their headers directories to that path. I finally compile the mavlink package and my package together and it works well. @vooon @zhangyongwei93 Thanks for your help~~~

lamhung81 commented 7 years ago

Hi all, We would like to create a new custom mavlink message to mavros, and transform to a ros topic form, for the purpose of transferring data from a new external pressure sensor in px4 to an on-board computer. We have followed all the steps that you have mentioned. Our platform includes Ubuntu 14.04, ROS indigo, PX4 v1.6.5 However, there some issues that we do need your help:

  1. We follows the tutorial to generate new mavlink header file http://qgroundcontrol.org/mavlink/create_new_mavlink_message However, in the generator interface, if "validate" option is chosen, then there are some errors preventing generate common.xml; If without "validate", there some warnings. If possible, could you tell us which generator (and which version) we should use? Do we need "validate" option?

  2. We found another mavlink generator in mavlink github. https://github.com/mavlink/mavlink Should we use this one?

  3. During PX4 compilation, we found that there compiler was searching for one id name (declared in mavlink v1.0 (after generating)) in v2.0. So, do we need to generate only v1.0 or also v2.0 of mavlink?

  4. There are two directories that contain mavlink v1.0 header files, one is in ROS ~/catkin_ws/build/mavlink/include/v1.0 and the other one is in the OS system ~/opt/ros/indigo/include/mavlink/v1.0; So what you have updated is that only for the OS system?

TSC21 commented 7 years ago

@lamhung81:

  1. https://github.com/ArduPilot/pymavlink - that's the generator. Though, you will require the full spec of the Mavlink package, so I advise you to generate the mavlink headers from the pymavlink version that comes from https://github.com/mavlink/mavlink;
  2. That's not another. pymavlink it is what generates your headers and it is included on the Mavlink repo.
  3. That depends if your you want to use Mavlink 2.0 capabilities or not. Since we already parse Mavlink 2.0 msgs on MAVROS, you can generate 2.0 msgs already;
  4. The first is generated from building the packages on your catkin_ws. The other one is the headers from the ROS mavlink package. And I don't understand your question. I advise to see what @JoonmoAhn did in https://github.com/mavlink/mavros/issues/783. Do not continue commenting on this issue, since it is closed already. If you have any issues, just open a new issue so it can be tracked.