Gecko MsgaPack

This provides a serialization mechanism for gecko messages. It is not part of gecko because I wanted to be modular and able to switch out to a different serialization package if I needed to.

• Msgpack for serialization of messages
• cppzmq is a header only, high level zmq

Install

The version of msgpack that comes with linux is old. Download and install a current version.

macOS

brew install msgpack

Linux

This will install the message formats into gecko in /usr/local.

cd gecko
mkdir build
cd build
cmake ..
make
make package
sudo dpkg -i gecko-x.x.x-linux.deb

Messages

Message formats are pulled from ROS. There are both common messages and time stamped messages.

Common Message Types (_t suffix)

• vec_t: 3D vector
• quaternion_t: 4D quaternion
• twist_t: linear(vec_t), angular(vec_t) rates
• pose_t: robot orientation (quaternion) and position (vector)
• wrench_t: force (vec_t), torque (vec_t)

Time Stamped Messages (_st suffix)

• imu_st: IMU measurement (acceleration, angular velocity, magnetometer)
• lidar_st: lidar measurements, an array of (angle [deg], range [m])

Should you need to change install location, you can change that during the make: cmake .. -DCMAKE_INSTALL_PREFIX=/home/kevin/.local.

Examples

The pub/sub examples below show how to use the msgpack adapter to do a simple UDS pub/sub service.

Subscriber

#include <string>
#include <gecko/gecko.hpp>
#include <gecko/msgpack/msgs.hpp>
#include <msgpack/msgpack_pub_sub.hpp>

using namespace std;

void sub()
{
    string endpt = zmqUDS("/tmp/0");
    Subscriber s;
    s.connect(endpt);

    MsgPack<imu_t> buffer;

    while (gecko::ok())
    {
        zmq::message_t msg = s.recv();
        imu_t m = buffer.unpack(msg);
        // do something with it ...
    }
}

int main(){
    sub();
    return 0;
}

Publisher

#include <string>
#include <iostream>
#include <gecko/gecko.hpp>
#include <gecko/msgpack/msgs.hpp>
#include <msgpack/msgpack_pub_sub.hpp>

using namespace std;

void pub()
{
    string endpt = zmqUDS("/tmp/0");
    Publisher p;
    p.bind(endpt);
    Rate rate(1);

    MsgPack<imu_t> buffer;

    while (gecko::ok())
    {
        vec_t a(1,2,3);
        imu_t b(a,a,a);  // create new timestamp
        zmq::message_t msg = buffer.pack(b);

        p.pub(msg);

        cout << "pub" << endl;
        rate.sleep();
    }
}

int main(){
    pub();
    return 0;
}

To Do

• Build message specific tools

  • echo
  • bag

• Add more messages

• Document how to add new messages

MIT License

Copyright (c) 2019 Kevin J. Walchko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.