assistengps 0.07: Bangle.js 2 now gets estimated time + lat/lon from the browser (~3x faster fix)

apps/assistedgps/ChangeLog

@@ -4,3 +4,4 @@
 0.04: Now turns GPS off after upload
 0.05: Fix regression in 0.04 that caused AGPS data not to get loaded
 0.06: Auto-set GPS output sentences - newer Bangle.js 2 don't include RMC (GPS direction + time) by default
+0.07: Bangle.js 2 now gets estimated time + lat/lon from the browser (~3x faster fix)

apps/assistedgps/custom.html

@@ -60,6 +60,7 @@
     <script>
       var isB1; // is Bangle.js 1?
       var isB2; // is Bangle.js 2?
+      var currentPosition;
 
       // When the 'upload' button is clicked...
       document.getElementById("upload").addEventListener("click", function() {
@@ -120,6 +121,7 @@
       }
 
 // =================================================== Bangle.js 2 CASIC
+// https://www.espruino.com/Bangle.js2+Technical#gps
 
     function CASIC_CHECKSUM(cmd) {
       var cs = 0;
@@ -128,6 +130,61 @@
       return cmd+"*"+cs.toString(16).toUpperCase().padStart(2, '0');
     }
 
+    // Send a binary CASIC packet, eg: {classId:6, messageId:0, payload:[]}
+    function CASIC_PKT(pkt) {
+      pkt.payload = pkt.payload || [];
+      var plen = pkt.payload.length;
+      var msg = new Uint8Array(10+pkt.payload.length);
+      msg.set([0xBA,0xCE,
+              plen, // LENGTH
+              0x00,
+              pkt.classId, // CLASS	ID
+              pkt.messageId]); // MESSAGE	ID
+      msg.set(pkt.payload, 6);
+      var dv = new DataView(msg.buffer);
+      // checksum
+      var ckSum = 0;
+      for (i = -4; i < plen; i+=4)
+        ckSum = 0|(ckSum+dv.getUint32(6+i, true));
+      dv.setUint32(6+plen, ckSum, true);
+      return msg;
+    }
+
+    // Send AID_INI message, {lat,lon,alt}
+    function AID_INI(pos) {
+      var msg = new Uint8Array(56);
+      var dv = new DataView(msg.buffer);
+      /*
+      double							xOrLat, yOrLon, zOrAlt;
+      double							tow; // 24
+      float							df; // 32
+      float							posAcc; // 36
+      float							tAcc; // 40
+      float							fAcc; // 44
+      unsigned int					res; // 48
+      unsigned short int				wn; // 52
+      unsigned char					timeSource; // 54
+      unsigned char					flags; // 55
+    */
+      var ms = Date.now();
+      var wk = (ms-new Date("1980-01-06T00:00:00Z")) / 604800000;
+      var wn = Math.floor(wk); // week number
+      var tow = (wk-wn) * 604800; // seconds in week
+      dv.setFloat64(0, pos.lat, true); // xOrLat
+      dv.setFloat64(8, pos.lon, true); // yOrLon
+      dv.setFloat64(16, pos.alt, true); // zOrAlt
+      dv.setFloat64(24, tow, true); // tow
+      dv.setFloat32(32, 0, true); // df
+      dv.setFloat32(36, 0, true); // posAcc
+      dv.setFloat32(40, 0, true); // tAcc
+      dv.setFloat32(44, 0, true); // fAcc
+      dv.setUint32(48, 0, true); // res
+      dv.setUint16(52, wn, true); // wn
+      dv.setUint8(54,0); // timeSource
+      dv.setUint8(55, 0x23); // flags ( lat/lon and clock valid, no drift data )
+      return CASIC_PKT({classId:0x0B, messageId:0x01, payload:msg});
+    }
+
 // ===================================================
 
       function jsFromBase64(b64) {
@@ -140,7 +197,6 @@
           js += `\x10Serial1.write(atob("${btoa(String.fromCharCode.apply(null,UBX_MGA_INI_TIME_UTC()))}"))\n`; // set GPS time
         }
         if (isB2) { // CASIC
-
           // Select what GNSS System to use for decreased fix time.
           var radios = document.getElementsByName('gnss_select');
           var gnss_select="1";
@@ -150,11 +206,11 @@
           js += `\x10var t=getTime()+0.5;while (getTime()<t);\n`; // This is nasty - but we just wait here until the GPS has had time to boot
           js += `\x10Serial1.println("${CASIC_CHECKSUM("$PCAS04,"+gnss_select)}")\n`; // set GNSS mode
           js += `\x10Serial1.println("${CASIC_CHECKSUM("$PCAS03,1,0,0,1,1,0,0,0")}")\n`; // enable GGA,GSV,RMC packets (new Bangle.js 2 GPS firmwares don't include RMC by default!)
+          // If the browser let us have the current location, give it to the GPS chip to get a faster fix
+          if (currentPosition) {
+            js += `\x10Serial1.write([${AID_INI(currentPosition).join(",")}])\n`;
+          }
           // Serial1.println("$PCAS06,0*1B") gets the current firmware version
-          // What about:
-          // NAV-TIMEUTC (0x01 0x10)
-          // NAV-PV (0x01 0x03)
-          // or AGPS.zip uses AID-INI (0x0B 0x01)
         }
 
         for (var i=0;i<bin.length;i+=chunkSize) {
@@ -184,7 +240,19 @@
         document.getElementById("banglejs1-info").style = isB1?"":"display:none";
         document.getElementById("banglejs2-info").style = isB2?"":"display:none";
         document.getElementById("upload-wrap").style = "";
+
+        if (isB2) {
+          // get current position for AGPS improvement
+          navigator.geolocation.getCurrentPosition(function(position) {
+            currentPosition = {
+              lat : position.coords.latitude,
+              lon : position.coords.longitude,
+              alt : 0|position.coords.altitude
+            };
+          });
         }
+      }
+
 
     </script>
   </body>

apps/assistedgps/metadata.json

@@ -2,7 +2,7 @@
   "id": "assistedgps",
   "name": "Assisted GPS Updater (AGPS)",
   "shortName": "AGPS",
-  "version": "0.06",
+  "version": "0.07",
   "description": "Downloads assisted GPS (AGPS) data to Bangle.js for faster GPS startup and more accurate fixes. **No app will be installed**, this just uploads new data to the GPS chip.",
   "sortorder": -1,
   "icon": "app.png",