Receiving Signal K

[antipole2]

It is desirable that the JavaScript plugin can be used to work with Signal K. Given the close relationship of both Signal K and JavaScript with JSON, this should be relatively easy to do and to use.

I do not have a Signal K set up and am away from my boat for the winter. So I am hoping SKS will work with me to establish this capability.

Receiving Signal K messages This should be possible with the existing JavaScript plugin release by using OCPN messaging. In future, it would be preferable to use the new streams interface but I think that is not yet complete in OCPN.

The following script should (not tested) receive three Signal K messages, parse them into a Javascript structure and then pretty -print them. Please someone copy the output to me.

// Listen out for SignalK messages and display
count = 3;  // number of messages to listen for
OCPNonMessageName(received, "OCPN_CORE_SIGNALK");

function received(message){
    signalK = JSON.parse(message);
    print(JSON.stringify(signalK, null, "\t"), "\n\n");     // pretty-print message
    if (--count > 0) OCPNonMessageName(received, "OCPN_CORE_SIGNALK");
    }

[Rasbats]

Running openplotter on RPi using feed from OpenCPN/ShipDriver. Local network with another instance of OpenCPN on Windows. This app using JScript_pi:

{
    "context": "vessels.urn:mrn:signalk:uuid:80eb056e-1b7a-4302-9c1a-96c05ba0e4d8",
    "updates": [
        {
            "source": {
                "talker": "II",
                "label": "opencpn",
                "sentence": "GLL",
                "type": "NMEA0183"
            },
            "$source": "opencpn.II",
            "timestamp": "2023-11-13T13:39:36.000Z",
            "values": [
                {
                    "path": "navigation.position",
                    "value": {
                        "latitude": 49.71504957,
                        "longitude": -3.5839755
                    }
                }
            ]
        }
    ]
}{
    "context": "vessels.urn:mrn:signalk:uuid:80eb056e-1b7a-4302-9c1a-96c05ba0e4d8",
    "updates": [
        {
            "source": {
                "talker": "II",
                "label": "opencpn",
                "sentence": "VTG",
                "type": "NMEA0183"
            },
            "$source": "opencpn.II",
            "timestamp": "2023-11-13T12:51:05.808Z",
            "values": [
                {
                    "path": "navigation.courseOverGroundMagnetic",
                    "value": null
                },
                {
                    "path": "navigation.courseOverGroundTrue",
                    "value": 1.221730477
                },
                {
                    "path": "navigation.speedOverGround",
                    "value": 0
                }
            ]
        }
    ]
}{
    "context": "vessels.urn:mrn:signalk:uuid:80eb056e-1b7a-4302-9c1a-96c05ba0e4d8",
    "updates": [
        {
            "source": {
                "talker": "II",
                "label": "opencpn",
                "sentence": "VHW",
                "type": "NMEA0183"
            },
            "$source": "opencpn.II",
            "timestamp": "2023-11-13T12:51:05.814Z",
            "values": [
                {
                    "path": "navigation.headingTrue",
                    "value": 1.221730477
                },
                {
                    "path": "navigation.speedThroughWater",
                    "value": 5.658890322
                }
            ]
        }
    ]
}result: undefined

[antipole2]

In the next update to the User Guide JavaScript_plugin_user_guide- SK.pdf