@jbroll/nmea-simple/codecs/MWV.ts

NMEA 0183 sentence parser and encoder

/*
 * === MWV - Wind speed and angle ===
 *
 * ------------------------------------------------------------------------------
 *        1   2 3   4 5
 *        |   | |   | |
 * $--MWV,x.x,a,x.x,a*hh<CR><LF>
 * ------------------------------------------------------------------------------
 *
 * Field Number:
 *
 * 1. Wind Angle, 0 to 360 degrees
 * 2. Reference, R = Relative, T = True
 * 3. Wind Speed
 * 4. Wind Speed Units, K/M/N
 * 5. Status, A = Data Valid
 * 6. Checksum
 */

import { createNmeaChecksumFooter, encodeDegrees, encodeFixed, parseFloatSafe } from "../helpers";
import { initStubFields, PacketStub } from "./PacketStub";


export const sentenceId: "MWV" = "MWV";
export const sentenceName = "Wind speed and angle";


export interface MWVPacket extends PacketStub<typeof sentenceId> {
    windAngle: number;
    reference: "relative" | "true";
    speed: number;
    units: "K" | "M" | "N";
    status: "valid" | "invalid";
}


export function decodeSentence(stub: PacketStub, fields: string[]): MWVPacket {
    return {
        ...initStubFields(stub, sentenceId, sentenceName),
        windAngle: parseFloatSafe(fields[1]),
        reference: fields[2] === "R" ? "relative" : "true",
        speed: parseFloatSafe(fields[3]),
        units: fields[4] === "K" ? "K" : fields[4] === "M" ? "M" : "N",
        status: fields[5] === "A" ? "valid" : "invalid"
    };
}


export function encodePacket(packet: MWVPacket, talker: string): string {
    const result = ["$" + talker + sentenceId];

    result.push(encodeDegrees(packet.windAngle));
    result.push(packet.reference === "relative" ? "R" : "T");
    result.push(encodeFixed(packet.speed, 2));
    result.push(packet.units === "K" ? "K" : packet.units === "M" ? "M" : "N");
    result.push(packet.status === "valid" ? "A" : "V");

    const resultWithoutChecksum = result.join(",");
    return resultWithoutChecksum + createNmeaChecksumFooter(resultWithoutChecksum);
}