Bluetooth UART support (#46)

Author: microbit-grace

lib/bluetooth-device-wrapper.ts

@@ -16,6 +16,7 @@ import {
   TypedServiceEvent,
   TypedServiceEventDispatcher,
 } from "./service-events.js";
+import { UARTService } from "./uart-service.js";
 
 const deviceIdToWrapper: Map<string, BluetoothDeviceWrapper> = new Map();
 
@@ -116,8 +117,9 @@ export class BluetoothDeviceWrapper {
     "buttonbchanged",
   ]);
   private led = new ServiceInfo(LedService.createService, []);
+  private uart = new ServiceInfo(UARTService.createService, ["uartdata"]);
 
-  private serviceInfo = [this.accelerometer, this.buttons, this.led];
+  private serviceInfo = [this.accelerometer, this.buttons, this.led, this.uart];
 
   boardVersion: BoardVersion | undefined;
 
@@ -385,6 +387,10 @@ export class BluetoothDeviceWrapper {
     return this.createIfNeeded(this.led, false);
   }
 
+  async getUARTService(): Promise<UARTService | undefined> {
+    return this.createIfNeeded(this.uart, false);
+  }
+
   async startNotifications(type: TypedServiceEvent) {
     const serviceInfo = this.serviceInfo.find((s) => s.events.includes(type));
     if (serviceInfo) {

lib/bluetooth.ts

@@ -273,4 +273,9 @@ export class MicrobitWebBluetoothConnection
     const ledService = await this.connection?.getLedService();
     ledService?.setLedMatrix(matrix);
   }
+
+  async writeUART(data: Uint8Array): Promise<void> {
+    const uartService = await this.connection?.getUARTService();
+    uartService?.writeData(data);
+  }
 }

lib/device.ts

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 import { TypedEventTarget } from "./events.js";
+import { UARTDataEvent } from "./uart.js";
 
 /**
  * Specific identified error types.
@@ -180,6 +181,7 @@ export class DeviceConnectionEventMap {
   "serialdata": SerialDataEvent;
   "serialreset": Event;
   "serialerror": SerialErrorEvent;
+  "uartdata": UARTDataEvent;
   "flash": Event;
   "beforerequestdevice": Event;
   "afterrequestdevice": Event;

lib/service-events.ts

@@ -1,11 +1,13 @@
 import { AccelerometerDataEvent } from "./accelerometer.js";
 import { ButtonEvent } from "./buttons.js";
 import { DeviceConnectionEventMap } from "./device.js";
+import { UARTDataEvent } from "./uart.js";
 
 export class ServiceConnectionEventMap {
   "accelerometerdatachanged": AccelerometerDataEvent;
   "buttonachanged": ButtonEvent;
   "buttonbchanged": ButtonEvent;
+  "uartdata": UARTDataEvent;
 }
 
 export type CharacteristicDataTarget = EventTarget & {

lib/uart-service.ts

@@ -0,0 +1,80 @@
+import { Service } from "./bluetooth-device-wrapper.js";
+import { profile } from "./bluetooth-profile.js";
+import { BackgroundErrorEvent, DeviceError } from "./device.js";
+import {
+  CharacteristicDataTarget,
+  TypedServiceEvent,
+  TypedServiceEventDispatcher,
+} from "./service-events.js";
+import { UARTDataEvent } from "./uart.js";
+
+export class UARTService implements Service {
+  constructor(
+    private txCharacteristic: BluetoothRemoteGATTCharacteristic,
+    private rxCharacteristic: BluetoothRemoteGATTCharacteristic,
+    private dispatchTypedEvent: TypedServiceEventDispatcher,
+    private queueGattOperation: <R>(action: () => Promise<R>) => Promise<R>,
+  ) {
+    this.txCharacteristic.addEventListener(
+      "characteristicvaluechanged",
+      (event: Event) => {
+        const target = event.target as CharacteristicDataTarget;
+        const value = new Uint8Array(target.value.buffer);
+        this.dispatchTypedEvent("uartdata", new UARTDataEvent(value));
+      },
+    );
+  }
+
+  static async createService(
+    gattServer: BluetoothRemoteGATTServer,
+    dispatcher: TypedServiceEventDispatcher,
+    queueGattOperation: <R>(action: () => Promise<R>) => Promise<R>,
+    listenerInit: boolean,
+  ): Promise<UARTService | undefined> {
+    let uartService: BluetoothRemoteGATTService;
+    try {
+      uartService = await gattServer.getPrimaryService(profile.uart.id);
+    } catch (err) {
+      if (listenerInit) {
+        dispatcher("backgrounderror", new BackgroundErrorEvent(err as string));
+        return;
+      } else {
+        throw new DeviceError({
+          code: "service-missing",
+          message: err as string,
+        });
+      }
+    }
+    const rxCharacteristic = await uartService.getCharacteristic(
+      profile.uart.characteristics.rx.id,
+    );
+    const txCharacteristic = await uartService.getCharacteristic(
+      profile.uart.characteristics.tx.id,
+    );
+    return new UARTService(
+      txCharacteristic,
+      rxCharacteristic,
+      dispatcher,
+      queueGattOperation,
+    );
+  }
+
+  async startNotifications(type: TypedServiceEvent): Promise<void> {
+    if (type === "uartdata") {
+      await this.txCharacteristic.startNotifications();
+    }
+  }
+
+  async stopNotifications(type: TypedServiceEvent): Promise<void> {
+    if (type === "uartdata") {
+      await this.txCharacteristic.stopNotifications();
+    }
+  }
+
+  async writeData(value: Uint8Array): Promise<void> {
+    const dataView = new DataView(value.buffer);
+    return this.queueGattOperation(() =>
+      this.rxCharacteristic.writeValueWithoutResponse(dataView),
+    );
+  }
+}

lib/uart.ts

@@ -0,0 +1,5 @@
+export class UARTDataEvent extends Event {
+  constructor(public readonly value: Uint8Array) {
+    super("uartdata");
+  }
+}

src/demo.ts

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  */
 import crelt from "crelt";
+import { AccelerometerDataEvent } from "../lib/accelerometer";
 import { MicrobitWebBluetoothConnection } from "../lib/bluetooth";
 import { ButtonEvent } from "../lib/buttons";
 import {
@@ -14,13 +15,10 @@ import {
   SerialDataEvent,
 } from "../lib/device";
 import { createUniversalHexFlashDataSource } from "../lib/hex-flash-data-source";
+import { UARTDataEvent } from "../lib/uart";
 import { MicrobitWebUSBConnection } from "../lib/usb";
 import { MicrobitRadioBridgeConnection } from "../lib/usb-radio-bridge";
 import "./demo.css";
-import {
-  AccelerometerData,
-  AccelerometerDataEvent,
-} from "../lib/accelerometer";
 
 type ConnectionType = "usb" | "bluetooth" | "radio";
 
@@ -64,6 +62,7 @@ const recreateUi = async (type: ConnectionType) => {
     createConnectSection(type),
     createFlashSection(),
     createSerialSection(),
+    createUARTSection(),
     createButtonSection("A", "buttonachanged"),
     createButtonSection("B", "buttonbchanged"),
     createAccelerometerSection(),
@@ -274,6 +273,80 @@ const createSerialSection = (): Section => {
   };
 };
 
+const createUARTSection = (): Section => {
+  if (!(connection instanceof MicrobitWebBluetoothConnection)) {
+    return {};
+  }
+
+  const uartDataListener = (event: UARTDataEvent) => {
+    const value = new TextDecoder().decode(event.value);
+    console.log(value);
+  };
+
+  const bluetoothConnection =
+    connection instanceof MicrobitWebBluetoothConnection
+      ? connection
+      : undefined;
+
+  let dataToWrite = "";
+  const dataToWriteFieldId = "dataToWrite";
+  const dom = crelt(
+    "section",
+    crelt("h2", "UART"),
+    crelt("h3", "Receive"),
+    crelt(
+      "button",
+      {
+        onclick: () => {
+          bluetoothConnection?.addEventListener("uartdata", uartDataListener);
+        },
+      },
+      "Listen to UART",
+    ),
+    crelt(
+      "button",
+      {
+        onclick: () => {
+          bluetoothConnection?.removeEventListener(
+            "uartdata",
+            uartDataListener,
+          );
+        },
+      },
+      "Stop listening to UART",
+    ),
+    crelt("h3", "Write"),
+    crelt("label", { name: "Data", for: dataToWriteFieldId }),
+    crelt("textarea", {
+      id: dataToWriteFieldId,
+      type: "text",
+      onchange: (e: Event) => {
+        dataToWrite = (e.currentTarget as HTMLInputElement).value;
+      },
+    }),
+    crelt(
+      "div",
+      crelt(
+        "button",
+        {
+          onclick: async () => {
+            const encoded = new TextEncoder().encode(dataToWrite);
+            await bluetoothConnection?.writeUART(encoded);
+          },
+        },
+        "Write to micro:bit",
+      ),
+    ),
+  );
+
+  return {
+    dom,
+    cleanup: () => {
+      connection.removeEventListener("uartdata", uartDataListener);
+    },
+  };
+};
+
 const createAccelerometerSection = (): Section => {
   if (
     !(