MQTT > NMEA 2000

[Geoff Higginbottom]

Hey Gang, quite new to this tech, but I have a question about how I get data onto the NMEA 2000 Bus.

I have data coming into a PI running OpenPlotter via a MQTT Message bus - data is being sent from a PI running Victron Venus, which is sending things like Battery Voltage etc.

My OpenPlotter PI has a PICAN-M N2K Hat and I can read data from the N2K Bus, but I cannot work out how to get data back onto the Bus.

I have this config currently, and have enabled the "Battery (127506 & 127508)" option in the SignalK to NMEA 2000 plugin, but do not know what I should be using for battery mappings etc

[{"id":"abed08c3f6d3b560","type":"mqtt in","z":"3069492ed761c9d6","name":"","topic":"batteryVoltage","qos":"2","datatype":"auto-detect","broker":"1f95090207bca94a","nl":false,"rap":true,"rh":0,"inputs":0,"x":150,"y":480,"wires":[["fc764886ff6ddcf4","b218e738964742ca"]]},{"id":"341bae7f21d9990f","type":"mqtt in","z":"3069492ed761c9d6","name":"","topic":"batteryCurrent","qos":"2","datatype":"auto-detect","broker":"1f95090207bca94a","nl":false,"rap":true,"rh":0,"inputs":0,"x":160,"y":560,"wires":[["b218e738964742ca"]]},{"id":"b218e738964742ca","type":"function","z":"3069492ed761c9d6","name":"Actisence String","func":"// Extract battery voltage and current from the message payload\nvar batteryVoltage = msg.payload.batteryVoltage; // Replace with your actual payload property\nvar batteryCurrent = msg.payload.batteryCurrent; // Replace with your actual payload property\n\n// Function to convert a floating-point number to its hexadecimal representation\nfunction floatToHex(f) {\n    return Buffer.from(Float32Array.from([f]).buffer).toString('hex');\n}\n\n// Convert battery voltage and current to hexadecimal\nvar hexVoltage = floatToHex(batteryVoltage);\nvar hexCurrent = floatToHex(batteryCurrent);\n\n// Construct the Actisense-formatted string\nvar actisenseString = `10EAFF${hexVoltage}${hexCurrent}`;\n\n// Set the formatted string in the message payload\nmsg.payload.actisenseString = actisenseString;\n\n// Return the modified message\nreturn msg;\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":400,"y":480,"wires":[["abcda3d2a27792db","67d37b2c0cad1e24"]]},{"id":"abcda3d2a27792db","type":"signalk-send-nmea2000","z":"3069492ed761c9d6","name":"","nmea2000Event":"nmea2000out","nmea2000JsonEvent":"nmea2000JsonOut","x":670,"y":440,"wires":[]},{"id":"1f95090207bca94a","type":"mqtt-broker","name":"","broker":"localhost","port":"1883","clientid":"","autoConnect":true,"usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willPayload":"","willMsg":{},"userProps":"","sessionExpiry":""}]

[Teppo Kurki]

We are no longer promoting this Google group / mailing list, instead preferring https://github.com/SignalK/signalk/discussions. Github discussions are more readily accessible to everybody and a great place to gather questions and answers for everybody to benefit from.

So please, post your message there and I promise a reply.

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[Bradford Harley]

I understand and appreciate the move to github.   I do have a question though....   It doesn't look like I can subscribe to the entire discussions section, just to threads individually.   This makes it harder to follow new topics and/or provide what limited assistance I can.    Am I missing something?

To view this discussion on the web visit https://groups.google.com/d/msgid/signalk/CAOyOCEAap_6yoj2JiFkamM0P4CtuKbHnkFUHBDohX%3Dc%2BYPr00w%40mail.gmail.com.

[Bradford Harley]

Disregard.   I figured out that I can watch from the main github page....