Broadcast rpm to socket server from mobile web

static/js/BLE.js

@@ -1,3 +1,7 @@
+let socket = null;
+let characteristic = null;
+let prevRes = null;
+
 function delay(ms) {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
@@ -13,10 +17,35 @@ async function connect(props) {
   console.log("Getting Service...");
   const service = await server.getPrimaryService("cycling_speed_and_cadence");
   console.log("Getting Characteristic...");
-  const characteristic = await service.getCharacteristic("csc_measurement");
+  characteristic = await service.getCharacteristic("csc_measurement");
   await characteristic.startNotifications();
   console.log("> Notifications started");
   characteristic.addEventListener("characteristicvaluechanged", props.onChange);
+  console.log("> Characteristic value changed event listener added");
+  socket = io();
+
+  socket.on("disconnect", (reason) => {
+    if (reason === "io server disconnect") {
+      // the disconnection was initiated by the server, you need to reconnect manually
+      socket.connect();
+    }
+    // else the socket will automatically try to reconnect
+  });
+}
+
+async function disconnect() {
+  if (characteristic) {
+    try {
+      await characteristic.stopNotifications();
+      log("> Notifications stopped");
+      characteristic.removeEventListener(
+        "characteristicvaluechanged",
+        handleNotifications
+      );
+    } catch (error) {
+      log("Argh! " + error);
+    }
+  }
 }
 
 function parseCSC(e) {
@@ -44,21 +73,23 @@ function parseCSC(e) {
     index += 2;
   }
   console.log("CSC", res);
-  const pre = document.createElement("pre");
-  pre.style.border = "1px solid red";
-  pre.textContent = JSON.stringify(res, null, 2);
-  document.body.appendChild(pre);
+  if (prevRes) {
+    let rpm = revsToRPM(prevRes, res);
+    if (rpm > 0)
+      socket.emit("message", { rpm: parseFloat(rpm.toFixed(2)), id: 1 });
+  }
+  prevRes = res;
   return res;
 }
 
-function revsToRPM(t1, t2) {
-  const deltaRevs = t2.revs - t1.revs;
+function revsToRPM(prevRes, res) {
+  const deltaRevs = res.crankRevs - prevRes.crankRevs;
   if (deltaRevs === 0) {
     // no rotation
     return 0;
   }
 
-  let deltaTime = (t2.time - t1.time) / 1024;
+  let deltaTime = (res.crankTime - prevRes.crankTime) / 1024;
   if (deltaTime < 0) {
     // time counter wraparound
     deltaTime += Math.pow(2, 16) / 1024;