@signalk/nmea0183-signalk/hooks/HSC.js

A node.js/javascript parser for NMEA0183 sentences. Sentences are parsed to Signal K format.

/**
 * Copyright 2019 Signal K and Fabian Tollenaar <fabian@decipher.industries>.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const debug = require('debug')('signalk-parser-nmea0183/HSC')
const utils = require('@signalk/nmea0183-utilities')

/**
 * $FTHSC,40.12,T,39.11,M*5E
 *
 * Heading Steering Command
 *
 * 0) 40.12         Heading to steer, degrees true
 * 1) T             True
 * 2) 39.11         Heading to steer, degrees magnetic
 * 3) M             Magnetic
 **/

module.exports = function HSCHook(input) {
  const { id, sentence, parts, tags } = input
  const upper = (str) => str.trim().toUpperCase()

  debug(`[HSCHook] decoding sentence ${id} => ${sentence}`)

  if (
    upper(parts[1]) === '' ||
    upper(parts[3]) === '' ||
    upper(parts[0]) === '' ||
    upper(parts[2]) === ''
  ) {
    return null
  }

  const headingToSteer = {}
  headingToSteer[upper(parts[1]) === 'T' ? 'True' : 'Magnetic'] =
    utils.transform(parts[0], 'deg', 'rad')
  headingToSteer[upper(parts[3]) === 'T' ? 'True' : 'Magnetic'] =
    utils.transform(parts[2], 'deg', 'rad')

  return {
    updates: [
      {
        source: tags.source,
        timestamp: tags.timestamp,
        values: [
          {
            path: 'steering.autopilot.target.headingTrue',
            value: headingToSteer.True || null,
          },
          {
            path: 'steering.autopilot.target.headingMagnetic',
            value: headingToSteer.Magnetic || null,
          },
        ],
      },
    ],
  }
}