implement ble connection and tidy up classes

src/connection/ble_connection.js

@@ -0,0 +1,95 @@
+import Constants from "../constants.js";
+import Connection from "./connection.js";
+
+class BleConnection extends Connection {
+
+    constructor(bleDevice) {
+        super();
+        this.bleDevice = bleDevice;
+        this.gattServer = null;
+        this.rxCharacteristic = null;
+        this.txCharacteristic = null;
+        this.init();
+    }
+
+    static async open() {
+
+        // ensure browser supports web bluetooth
+        if(!navigator.bluetooth){
+            alert("Web Bluetooth is not supported in this browser");
+            return;
+        }
+
+        // ask user to select device
+        const device = await navigator.bluetooth.requestDevice({
+            filters: [
+                {
+                    services: [
+                        Constants.Ble.ServiceUuid.toLowerCase(),
+                    ],
+                },
+            ],
+        });
+
+        // make sure user selected a device
+        if(!device){
+            return null;
+        }
+
+        return new BleConnection(device);
+
+    }
+
+    async init() {
+
+        // connect to gatt server
+        this.gattServer = await this.bleDevice.gatt.connect();
+
+        // find service
+        const service = await this.gattServer.getPrimaryService(Constants.Ble.ServiceUuid.toLowerCase());
+        const characteristics = await service.getCharacteristics();
+
+        // find rx characteristic (we write to this one, it's where the radio reads from)
+        this.rxCharacteristic = characteristics.find((characteristic) => {
+            return characteristic.uuid.toLowerCase() === Constants.Ble.CharacteristicUuidRx.toLowerCase();
+        });
+
+        // find tx characteristic (we read this one, it's where the radio writes to)
+        this.txCharacteristic = characteristics.find((characteristic) => {
+            return characteristic.uuid.toLowerCase() === Constants.Ble.CharacteristicUuidTx.toLowerCase();
+        });
+
+        // listen for frames from transmitted to us from the ble device
+        await this.txCharacteristic.startNotifications();
+        this.txCharacteristic.addEventListener('characteristicvaluechanged', (event) => {
+            const frame = new Uint8Array(event.target.value.buffer);
+            this.onFrameReceived(frame);
+        });
+
+    }
+
+    async close() {
+        try {
+            this.gattServer?.disconnect();
+            this.gattServer = null;
+        } catch(e) {
+            // ignore error when disconnecting
+        }
+    }
+
+    async write(bytes) {
+        try {
+            // we write to the rx characteristic, as that's where the radio reads from
+            await this.rxCharacteristic.writeValue(bytes);
+        } catch(e) {
+            console.log("failed to write to ble device", e);
+        }
+    }
+
+    async sendToRadioFrame(data) {
+        await this.write(data);
+    }
+
+}
+
+export default BleConnection;