antipole2
commented
1 year ago @duichan Ready to start Step 1 testing - receiving NMEA2000 messages. You will need build 9a03cee (20 Oct ca 09:030) or later.
Please run the following script
// capture samples of NMEA2000 data as returned to this plugin
// Alpha testing - details may change
pgns = [ // pgns to sample
129029, // GNSS Position Data
129540, // GNSS Sats in View
130306 // Wind Data
];
timeLimit = 10; // seconds
onSeconds(timeout, timeLimit);
count = pgns.length;
for (i = 0; i < pgns.length; i++){
OCPNonNMEA2k(gotOne, pgns[i]); // listen out
}
function gotOne(input){
print(count, "\t", input, "\n");
if (count-- <= 1){ // all done
onSeconds(); // cancel timer
stopScript("All done");
}
}
function timeout(){
scriptResult("Timed out with count=" + count);
print(consoleDump());
OCPNonNMEA2k(); // cancel outstanding listeners
}It sets up an array of pgns, listens out for them and displays the received data. I need to see what this data looks like when received into the script. The script will stay busy until all pgns have been received. There is a timeout set of 10 seconds. If all messages have not been received in that time, it will dump internal stuff to help see what is going on. You can adjust the time as required. You can amend or add to the pgn array if those I have chosen are not right for your set up.
I have run this script substituting all occurrences of OCPNonNMEA2k with OCPNonNMEA0183 and the pgns with NMEA0183 sentence types and it works as intended. I then cloned the OCPNonNMEA0183 code and adapted it for OCPNonNMEA2k. I have not been able to test this for lack of NMEA2k input.
The User Guide would help you understand the OCPN part of the plugin but does not include the new
OCPNonNMEA2k(functionToCall, pgn); // listen out for pgn and pass input to functionToCall
Calling it with no arguments will cancel outstanding listeners.
duichan
TwoCanPlugIn
Unlike NMEA0183, which uses a simple text format, NMEA2k messages are binary and unintelligible to the eye. Further, the binary forms is proprietary and only available to licence holders. However, the canboat project has reverse-engineered many of the PGNs and published PGN descriptors.
OCPN can receive NMEA2k messages and has built-in decoders for the common PGNs. These are used by the dashboard plugin. Extending the JavaScript plugin to use all these built-in decoders would be significant work and a lot of code.
JavaScript is ideal for testing and experimentation, so rather than depending on the limited set of built-in decoders, I am aiming to decode any PGN for which there is a PGN descriptor within JavaScript.
There is a JavaScript version of canboat but it is large and complicated and relies heavily on the latest features of JavaScript not available in the Duktape JavaScript engine used in the plugin. It can be used for insights in how to do various bits but is not generally usable for our current purpose.
The task becomes: Step 1: Extend the plugin to listen for NMEA2k messages and pass the raw payload to the script. Step2: Write a function that will parse any payload for which there is a PGN descriptor and return the data as a JavaScript object.