Help on getting telemetry stream

[davebest]

I'm using ArduSub and am creating a stand-alone program to retrieve the depth of the ROV and output it as an NMEA-0183 message. I would like send a PARAM_REQUEST_READ message and receive the stream over UDP.

Looking at the examples I'm not sure if I should connect as a udp-client, or udp-broadcast, since I'd like the stream to be directed rather than broadcast.
I have studied the examples and looked a bit into the source code, but I'm afraid I'm stumped. I have tried to include the message to dialect.Messages, with no success:

msgs := []msg.Message{}
msgs = append(msgs, &common.MessageParamRequestRead{1, 1, "", 6})
dialect := ardupilotmega.Dialect
dialect.Messages = msgs
node, err := gomavlib.NewNode(gomavlib.NodeConf{
    Endpoints: []gomavlib.EndpointConf{
        gomavlib.EndpointUDPBroadcast{
            BroadcastAddress: "192.168.2.255:14550",
            LocalAddress:     ":14550",
        },
    },
    Dialect:                dialect,
    OutVersion:             gomavlib.V2, // change to V1 if you're unable to communicate with the target
    OutSystemID:            10,
    StreamRequestEnable:    true,
    StreamRequestFrequency: 4,
})

Any help would be appreciated. A new example showing this common requirement might be helpful for all.

[aler9]

Hello, the common dialect is already included in the ardupilotmega dialect, so there's no need to add MessageParamRequestRead again:

https://github.com/mavlink/mavlink/blob/1eac49b6d8c00d4051ff6713e5c49088cf75f7c5/message_definitions/v1.0/ardupilotmega.xml#L3

Regarding the communication issue, it strongly depends on what you're communicating with. The target must explicitly have a open UDP port that accepts Mavlink. UDP client usually works, there's no need of using UDP broadcast. The only advice i can give is to try to read before trying to send; once you've successfully received a message, you can easily send one back.

[davebest]

Thank you. I added "--out udpin=192.168.2.2:14555" to the mavproxy config on the ROV and am able to connect to it with the UDP client. In my setup mavproxy on the ROV is broadcasting heartbeats on 192.168.2.255:14550. How can I can listen for a heartbeat message and get the sender ip and port from it, so that I can then do a UDP client connect to it (similar to how QGroundControl does it)?

…

On Aug 12, 2021, at 3:15 AM, Alessandro Ros ***@***.***> wrote: Hello, the common dialect is already included in the ardupilotmega dialect, so there's no need to add MessageParamRequestRead again: https://github.com/mavlink/mavlink/blob/1eac49b6d8c00d4051ff6713e5c49088cf75f7c5/message_definitions/v1.0/ardupilotmega.xml#L3 Regarding the communication issue, it strongly depends on what you're communicating with. The target must explicitly have a open UDP port that accepts Mavlink. UDP client usually works, there's no need of using UDP broadcast. The only advice i can give is to try to read before trying to send; once you've successfully received a message, you can easily send one back. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe. Triage notifications on the go with GitHub Mobile for iOS or Android.

[aler9]

In my setup mavproxy on the ROV is broadcasting heartbeats on 192.168.2.255:14550. How can I can listen for a heartbeat message and get the sender ip and port from it, so that I can then do a UDP client connect to it (similar to how QGroundControl does it)?

This is a complex technique that unfortunately you'd have to implement by scratch if you want to use the library, but i can suggest a simpler approach:

1. replace mavproxy with https://github.com/aler9/mavp2p
2. mavp2p allows you to choose exactly what protocol you want to use to communicate with the ROV through serial. Choose a protocol and use it directly, without using a third one (broadcast). For instance:

./mavp2p serial:/dev/ttyAMA0:57600 udps:0.0.0.0:5600

then connect to rov_ip:5600