@signalk/nmea0183-signalk/hooks/seatalk/0x84.js

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

/**
 * Copyright 2016 Signal K <info@signalk.org> and contributors.
 *
 * 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.
 */

'use strict'

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

/*
84  U6  VW  XY 0Z 0M RR SS TT  Compass heading  Autopilot course and
                  Rudder position (see also command 9C)
                  Compass heading in degrees:
                    The two lower  bits of  U * 90 +
                    the six lower  bits of VW *  2 +
                    number of bits set in the two higher bits of U =
                    (U & 0x3)* 90 + (VW & 0x3F)* 2 + (U & 0xC ? (U & 0xC == 0xC ? 2 : 1): 0)
                  Turning direction:
                    Most significant bit of U = 1: Increasing heading, Ship turns right
                    Most significant bit of U = 0: Decreasing heading, Ship turns left
                  Autopilot course in degrees:
                    The two higher bits of  V * 90 + XY / 2
                  Z & 0x2 = 0 : Autopilot in Standby-Mode
                  Z & 0x2 = 2 : Autopilot in Auto-Mode
                  Z & 0x4 = 4 : Autopilot in Vane Mode (WindTrim), requires regular "10" datagrams
                  Z & 0x8 = 8 : Autopilot in Track Mode
                  M: Alarms + audible beeps
                    M & 0x04 = 4 : Off course
                    M & 0x08 = 8 : Wind Shift
                  Rudder position: RR degrees (positive values steer right,
                    negative values steer left. Example: 0xFE = 2° left)
                  SS & 0x01 : when set, turns off heading display on 600R control.
                  SS & 0x02 : always on with 400G
                  SS & 0x08 : displays “NO DATA” on 600R
                  SS & 0x10 : displays “LARGE XTE” on 600R
                  SS & 0x80 : Displays “Auto Rel” on 600R
                  TT : Always 0x08 on 400G computer, always 0x05 on 150(G) computer
*/

module.exports = function (input) {
  const { id, sentence, parts, tags } = input
  var mode

  if (parts.length != 9) {
    return null
  }

  var U = parseInt(parts[1].charAt(0), 16)
  var VW = parseInt(parts[2], 16)
  var V = parseInt(parts[2].charAt(0), 16)
  var XY = parseInt(parts[3], 16)
  var Z = parseInt(parts[4].charAt(1), 16)
  var M = parseInt(parts[5].charAt(1), 16)
  var RR = parseInt(parts[6], 16)
  var SS = parseInt(parts[7], 16)
  var TT = parseInt(parts[8], 16)

  const inputs = [U, VW, V, XY, Z, M, RR, SS, TT]
  if (!inputs.every((x) => !isNaN(x))) {
    return null
  }

  var compassHeading =
    (U & 0x3) * 90 +
    (VW & 0x3f) * 2 +
    (U & 0xc ? (U & (0xc == 0xc) ? 2 : 1) : 0)
  var apCourse = ((V & 0xc) >> 2) * 90 + XY / 2
  /*Positive to right*/
  var rudderPos = RR
  if (rudderPos > 127) {
    rudderPos = rudderPos - 256
  }

  var modeVar = Z & 0x2
  switch (modeVar) {
    case 0:
      mode = 'standby'
      break
    case 2:
      mode = 'auto'
      break
    default:
      break
  }
  if ((Z & 0x4) == 4) {
    mode = 'wind'
  }
  if ((Z & 0x8) == 8) {
    mode = 'route'
  }
  var pathValues = []
  if (compassHeading) {
    pathValues.push({
      path: 'navigation.headingMagnetic',
      value: utils.transform(utils.float(compassHeading), 'deg', 'rad'),
    })
  }
  if (apCourse) {
    pathValues.push({
      path: 'steering.autopilot.target.headingMagnetic',
      value: utils.transform(utils.float(apCourse), 'deg', 'rad'),
    })
  }
  if (rudderPos) {
    pathValues.push({
      path: 'steering.rudderAngle',
      value: utils.transform(utils.float(rudderPos), 'deg', 'rad'),
    })
  }
  if (mode) {
    pathValues.push({
      path: 'steering.autopilot.state',
      value: mode,
    })
  }

  return {
    updates: [
      {
        source: tags.source,
        timestamp: tags.timestamp,
        values: pathValues,
      },
    ],
  }
}