go-mavlink

This is a fork of ungerik's MAVLink protocol Go implementation that fixes a panic condition upon first run after reboot with serial link connected PX4.

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MAVLink or Micro Air Vehicle Link is a protocol for communicating with small unmanned vehicle. It's designed as a header-only message marshaling library. MAVLink was first released early 2009 by Lorenz Meier under LGPL license.

This implementation is mainly inspired by the C version (see on GitHub). Only tested under Unix

Usage

Here two quick examples to understand how to deal with it but first, look at the MavPacket definition.

MavPacket definition :

type Message interface {
        ID() uint8
        Size() uint8
}

type MavHeader struct {
        FrameStart     uint8
        PayloadLength  uint8
        PacketSequence uint8
        SystemID       uint8
        ComponentID    uint8
        MessageID      uint8
}

type MavPacket struct {
        Header   MavHeader
        Msg      Message
        Checksum uint16
}

You got all the message definitions in message.go.

UDP communication (receiving example)

package main

import (
	"bufio"
	"fmt"
	mav "github.com/Sabmit/go-mavlink"
	"log"
	"net"
)

func main() {
	laddr, _ := net.ResolveUDPAddr("udp", "127.0.0.1:14550")
	conn, _ := net.ListenUDP("udp", laddr) // check errors

	parser := mav.GetMavParser()
    reader := bufio.NewReader(conn)

    for {
    	c, _ := reader.ReadByte() // check errors

        packet, err := parser(c)
        if err != nil {
        	log.Fatalf("Parser error: ", err)
        } else if packet != nil {
        	fmt.Println("Packet received :", packet.Bytes())
    	}
	}
}

The C server is available here, you can also test it by hand...

$ echo -ne "\xfe\x09\x0\x01\xC8\x00\x0\x0\x0\x0\x0\x0\x0\x0\x0\x5A\x3E" | nc -u 127.0.0.1 14550

Serial communication (Sending example)

import (
	"github.com/tarm/goserial"
	mav "github.com/Sabmit/go-mavlink"
       "log"
)

func main() {
	port := &serial.Config{Name: "/dev/ttyUSB0", Baud: 57600}
        s, _ := serial.OpenPort(port) // check errors

	message := new(mav.RequestDataStream)
        message.ReqMessageRate = 20

        err := mav.Send(s, 1, 200, message)
        if err != nil {
		log.Fatalf("Error while sending the packet:", err)
	}
}

More

The operation is simple : get the MavParser and then, parse each received byte untill you get a non-nil pointer pointing to the full MavPacket.

Please read main_udp.go and main_serial.go if you want the full code examples.

TO-DO

• For now, only the received packet has its own checksum computed on the go
• Verify if all properties of each message is in its own place (see Mavlink generator)

See

• Mavlink documentation
• QGroundControl

Authors

ungerik
sabmit