Add Xiaomi Mijia temperature sensor display

apps/mitherm/ChangeLog

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+0.01: Create mitherm app with support for pvvx firmware only

apps/mitherm/README.md

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+Reads BLE advertisement data from Xiaomi temperature/humidity sensors running the
+`pvvx` custom firmware (https://github.com/pvvx/ATC_MiThermometer).
+
+## Features
+
+* Display temperature
+* Display humidity
+* Display battery state of sensor
+* Auto-refresh every 5 minutes
+* Manual refresh on demand
+* Add aliases for MAC addresses to easily recognise devices
+
+## Planned features
+
+* Supprt for other advertising formats:
+  * atc1441 format
+  * BTHome
+  * Xiaomi Mijia format
+* Configurable auto-refresh interval
+* Configurable scan length (currently 30s)
+* Alerts when temperature outside defined limits (with a widget or bootcode to
+  work when app is inactive)

apps/mitherm/app-icon.js

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+require("heatshrink").decompress(atob("mEwwhC/AH4Ac5gWVhnM4AWVAAIYTCwQABCywYRIoYADJJwWHDB4RD5sz7hJPFIlP//0MRxFE6f/AAM9JJgWE4gWCAANMDBZcEn4XE+ZiKFwhcBCYPdDYRiEGAoXDLgf97vfMQwXILggXFMQYXHLgoXB6czMQoXHLgQXJMQQXG4YWEI44ABngXGh4XHF4v/+DAGC6DXGC5BHGC509F4IXTdwIABV4gXOIwIABJAoX/C6p3Xa4a/UABAXfgczABswC/4XmAH4A/ABY"))

apps/mitherm/app.js

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+var filterTemperature = [{
+  serviceData: {
+    "181a": {}
+  }
+}];
+var results = {};
+var macs = [];
+
+var aliases = require("Storage").readJSON("mitherm.json", true);
+if (!aliases) aliases = {};
+
+var lastSeen = {};
+var current = 0;
+var scanning = false;
+var timeoutDraw;
+var timeoutScan;
+
+
+const scan = function() {
+  if (!scanning) { // Don't start scanning if already doing so.
+    scanning = true;
+    if (timeoutScan) clearTimeout(timeoutScan);
+    timeoutScan = setTimeout(scan, 300000); // Scan again in 5 minutes.
+    drawScanState(scanning);
+    NRF.findDevices(function(devices) {
+      onDevices(devices);
+    }, {
+      filters: filterTemperature,
+      timeout: 30000  // Scan for 30s
+    });
+  }
+};
+
+
+const onDevices = function(devices) {
+  let now = Date.now();
+  for (let i = 0; i < devices.length; i++) {
+    let device = devices[i];
+
+    let processedData = extractData(device.data);
+    console.log({
+      rssi: device.rssi,
+      data: processedData
+    });
+    if (!macs.includes(processedData.MAC)) {
+      macs.push(processedData.MAC);
+    }
+    results[processedData.MAC] = processedData;
+    lastSeen[processedData.MAC] = now;
+  }
+  console.log("Scan complete.");
+  scanning = false;
+  writeOutput();
+};
+
+
+const extractData = function(thedata) {
+  let data = DataView(thedata);
+  let MAC = [];
+  for (let i = 9; i > 3; i--) {
+    MAC.push(data.getUint8(i, true).toString(16).padStart(2, "0"));
+  }
+  out = {
+    size: data.getUint8(0, true),
+    uid: data.getUint8(1, true),
+    UUID: data.getUint16(2, true),
+    MAC: MAC.join(":"),
+    temperature: data.getInt16(10, true) * 0.01,
+    humidity: data.getUint16(12, true) * 0.01,
+    battery_mv: data.getUint16(14, true),
+    battery_level: data.getUint8(16, true),
+  };
+  return out;
+};
+
+
+const writeOutput = function() {
+  let now = Date.now();
+  if (timeoutDraw) clearTimeout(timeoutDraw);
+  timeoutDraw = setTimeout(writeOutput, 60000); // Refresh in 1 minute.
+  g.clear(true);
+  Bangle.drawWidgets();
+  g.reset();
+  drawScanState(scanning);
+
+  if (macs.length == 0) return;
+
+  processedData = results[macs[current]];
+  g.setFont12x20(2);
+  g.drawString(`${processedData.temperature.toFixed(2)}°C`, 10, 30);
+  g.drawString(`${processedData.humidity.toFixed(2)} %`, 10, 70);
+
+  g.setFont6x15();
+  g.drawString(`${((now - lastSeen[macs[current]]) / 60000).toFixed(0)} min ago`, 10, 130);
+  g.drawString(`${processedData.battery_level} % battery`, 80, 130);
+  g.drawString(` ${processedData.MAC in aliases ? aliases[processedData.MAC] : processedData.MAC}: ${current + 1} / ${macs.length}`, 10, 150);
+};
+
+
+const scrollDevices = function(directionLR) {
+  // Swipe left or right to move between devices.
+  current -= directionLR; // inverted feels a more familiar gesture.
+  if (current + 1 > macs.length)
+    current = 0;
+  if (current < 0)
+    current = macs.length - 1;
+  writeOutput();
+};
+
+const drawScanState = function(state) {
+  if (state)
+    g.fillRect(160, 160, 170, 170);
+  else
+    g.clearRect(160, 160, 170, 170);
+};
+
+const setAlias = function(mac, alias) {
+  if (alias === "") {
+    delete aliases[mac];
+  }
+  else {
+    aliases[mac] = alias;
+    require("Storage").writeJSON("mitherm.json", aliases);
+  }
+};
+
+const changeAlias = function(mac) {
+  g.clear();
+  require("textinput").input((mac in aliases) ? aliases[mac] : "").then(function(text) {
+    setAlias(mac, text);
+    setUI();
+    writeOutput();
+  });
+};
+
+
+const setUI = function() {
+  Bangle.setUI({
+    mode: "custom",
+    swipe: scrollDevices,
+    btn: function() {
+      E.showMenu(actionsMenu);
+    }
+  });
+};
+
+
+const actionsMenu = {
+  "": {
+    "title": "-- Actions --",
+    "back": function() {
+      E.showMenu();
+    },
+    "remove": function() {
+      setUI();
+      writeOutput();
+    },
+  },
+  "Scan now": function() {
+    scan();
+    E.showMenu();
+  },
+  "Edit alias": function() {
+    changeAlias(macs[current]);
+  },
+};
+
+setUI();
+Bangle.loadWidgets();
+g.setClipRect(Bangle.appRect);
+scan();
+writeOutput();

apps/mitherm/metadata.json

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+{
+  "id": "mitherm",
+  "name": "Xiaomi Mijia Temperature and Humidity display",
+  "shortName": "MiTherm",
+  "version": "0.01",
+  "description": "Reads and displays data from Xiaomi temperature/humidity sensors running custom firmware",
+  "icon": "app.png",
+  "tags": "xiaomi,mi,ble,bluetooth,thermometer,humidity",
+  "readme": "README.md",
+  "supports": ["BANGLEJS", "BANGLEJS2"],
+  "storage": [
+    {"name":"mitherm.app.js","url":"app.js"},
+    {"name":"mitherm.img","url":"app-icon.js","evaluate":true}
+  ]
+}