108 lines
3.0 KiB
JavaScript
108 lines
3.0 KiB
JavaScript
let socket = null;
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let characteristic = null;
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let prevRes = null;
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function delay(ms) {
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return new Promise((resolve) => setTimeout(resolve, ms));
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}
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async function connect(props) {
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const device = await navigator.bluetooth.requestDevice({
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filters: [{ services: ["cycling_speed_and_cadence"] }],
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acceptAllDevices: false,
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});
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console.log(`%c\n👩🏼⚕️`, "font-size: 82px;", "Starting CSC...\n\n");
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const server = await device.gatt.connect();
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await delay(500);
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console.log("Getting Service...");
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const service = await server.getPrimaryService("cycling_speed_and_cadence");
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console.log("Getting Characteristic...");
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characteristic = await service.getCharacteristic("csc_measurement");
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await characteristic.startNotifications();
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console.log("> Notifications started");
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characteristic.addEventListener("characteristicvaluechanged", props.onChange);
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console.log("> Characteristic value changed event listener added");
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socket = io();
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socket.on("disconnect", (reason) => {
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if (reason === "io server disconnect") {
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// the disconnection was initiated by the server, you need to reconnect manually
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socket.connect();
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}
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// else the socket will automatically try to reconnect
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});
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}
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async function disconnect() {
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if (characteristic) {
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try {
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await characteristic.stopNotifications();
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log("> Notifications stopped");
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characteristic.removeEventListener(
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"characteristicvaluechanged",
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handleNotifications
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);
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} catch (error) {
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log("Argh! " + error);
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}
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}
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}
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function parseCSC(e) {
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const value = e.target.value;
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const flags = value.getUint8(0, true);
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const hasWheel = !!(flags & 0x01);
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const hasCrank = !!(flags & 0x02);
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let index = 1;
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const res = {
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wheelRevs: null,
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wheelTime: null,
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crankRevs: null,
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crankTime: null,
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};
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if (hasWheel) {
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res.wheelRevs = value.getUint32(index, true);
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index += 4;
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res.wheelTime = value.getUint16(index, true);
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index += 2;
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}
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if (hasCrank) {
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res.crankRevs = value.getUint16(index, true);
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index += 2;
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res.crankTime = value.getUint16(index, true);
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index += 2;
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}
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console.log("CSC", res);
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if (prevRes) {
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let rpm = revsToRPM(prevRes, res);
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if (rpm > 0)
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socket.emit("message", { rpm: parseFloat(rpm.toFixed(2)), id: 1 });
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}
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prevRes = res;
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return res;
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}
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function revsToRPM(prevRes, res) {
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const deltaRevs = res.crankRevs - prevRes.crankRevs;
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if (deltaRevs === 0) {
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// no rotation
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return 0;
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}
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let deltaTime = (res.crankTime - prevRes.crankTime) / 1024;
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if (deltaTime < 0) {
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// time counter wraparound
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deltaTime += Math.pow(2, 16) / 1024;
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}
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deltaTime /= 60; // seconds to minutes
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const rpm = deltaRevs / deltaTime;
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return rpm;
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}
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document.querySelector("#ble-connect").addEventListener("click", () =>
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connect({
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onChange: parseCSC,
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}).catch(console.error)
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);
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