Heart rate starting 'NULL' before giving heartrate

[Adeline.Joy]

Hi,

I've been using some code from this watch face (https://github.com/Fitbit/sdk-moment/blob/master/app/simple/hrm.js), to get the heart-zone indication. It is working, but my clockface was declined due to it displaying 'NULL' when I start up my watchface. Apparently it has to be '--', but I cannot seem to find the problem. I tried changing many things in the code, but no success so far.

Hope someone can help me

/*
  Returns the Heart Rate BPM, with off-wrist detection.
  Callback raised to update your UI.
*/
import { me } from "appbit";
import { display } from "display";
import { HeartRateSensor } from "heart-rate";
import { user } from "user-profile";

let hrm, watchID, hrmCallback;
let lastReading = 0;
let heartRate;

export function initialize(callback) {
  if (me.permissions.granted("access_heart_rate") && me.permissions.granted("access_user_profile")) {
    hrmCallback = callback;
    hrm = new HeartRateSensor();
    setupEvents();
    start();
    lastReading = hrm.timestamp;
  } else {
    console.log("Denied Heart Rate or User Profile permissions");
    callback({
      bpm: "???",
      zone: "denied",
      restingHeartRate: "???"
    });
  }
}

function getReading() {
  if (hrm.timestamp === lastReading) {
    heartRate = "--";
  } else {
    heartRate = hrm.heartRate;
  }
  lastReading = hrm.timestamp;
  hrmCallback({
    bpm: heartRate,
    zone: user.heartRateZone(hrm.heartRate || 0),
    restingHeartRate: user.restingHeartRate
  });
}

function setupEvents() {
  display.addEventListener("change", function() {
    if (display.on) {
      start();
    } else {
      stop();
    }
  });
}

function start() {
  if (!watchID) {
    hrm.start();
    getReading();
    watchID = setInterval(getReading, 1000);
  }
}

function stop() {
  hrm.stop();
  clearInterval(watchID);
  watchID = null;
}

[gnitz]

Within your index.gui you can set the default text for the element to "--", and have it be changed by your code on startup. You may also want to test scenarios where the watch is suddenly taken off the hand when screen is on.