Respond to MAVLINK 2 PROTOCOL_VERSION request

[jonathanreeves]

MAVSDK comfortably supports MAVLINK 2, but the server component doesn't currently respond to the MAVLINK_MSG_ID_PROTOCOL_VERSION request, and thus GCSes like QGroundControl fall back to MAVLINK 1 when establishing communication.

This change adds the MAVLINK_MSG_ID_PROTOCOL_VERSION handler with a corresponding capability to communicate to clients that MAVLINK 2 is supported.

QGroundControl log before:

InitialConnectStateMachineLog: Sending REQUEST_MESSAGE:PROTOCOL_VERSION
VehicleLog: _waitForMavlinkMessage msg:timeout 300 1000
...
InitialConnectStateMachineLog: REQUEST_MESSAGE PROTOCOL_VERSION command acked but message never received
InitialConnectStateMachineLog: "Setting _maxProtoVersion to 100 due to timeout on receiving PROTOCOL_VERSION message."
VehicleLog: _setMaxProtoVersionFromBothSources using protocol version message
VehicleLog: _setMaxProtoVersion before:after 200 100

QGroundControl log after:

InitialConnectStateMachineLog: Sending REQUEST_MESSAGE:PROTOCOL_VERSION
VehicleLog: _waitForMavlinkMessage msg:timeout 300 1000
VehicleLog: _sendMavCommandFromList command:tryCount "MAV_CMD_REQUEST_MESSAGE" 0
MissionControllerLog: _recalcFlightPathSegments homePositionValid false
VehicleLog: _waitForMavlinkMessageMessageReceived message received 300
VehicleLog: _waitForMavlinkMessageClear
VehicleLog: "_handleCommandAck command(MAV_CMD_REQUEST_MESSAGE) result(MAV_RESULT_ACCEPTED)"
InitialConnectStateMachineLog: PROTOCOL_VERSION received mav_version: 300
VehicleLog: _setMaxProtoVersionFromBothSources using protocol version message

[JonasVautherin]

Thanks!

I didn't know that QGC was checking the version like this 👍. I just have a nitpick on the format of the static constexpr 👍.

[JonasVautherin]

Looking at other static constexpr in the project, it feels like they are usually written more like this:

Suggested change

	static constexpr mavlink_protocol_version_t kMavlinkVersionInfo{
	static constexpr mavlink_protocol_version_t MAVLINK_VERSION_INFO {

[jonathanreeves]

Good call, sorry I should have looked at that more carefully. Change pushed to my fork and re-tested, thanks for the review and feedback!

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[julianoes]

Thanks!