microbit-web-bluetooth/src/services/uart.ts

Web Bluetooth library for micro:bit

/*
* micro:bit Web Bluetooth
* Copyright (c) 2019 Rob Moran
*
* The MIT License (MIT)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the 'Software'), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/

import { EventDispatcher, TypedDispatcher } from '../event-dispatcher';
import { ServiceHelper } from '../service-helper';

/**
 * @hidden
 */
export enum UartCharacteristic {
    tx = '6e400002-b5a3-f393-e0a9-e50e24dcca9e',
    rx = '6e400003-b5a3-f393-e0a9-e50e24dcca9e'
}

/**
 * Events raised by the UART service
 */
export interface UartEvents {
    /**
     * @hidden
     */
    newListener: keyof UartEvents;
    /**
     * @hidden
     */
    removeListener: keyof UartEvents;
    /**
     * Serial data received event
     */
    receive: Uint8Array;
    /**
     * Serial received text event
     */
    receiveText: string;
}

/**
 * UART Service
 */
export class UartService extends (EventDispatcher as new() => TypedDispatcher<UartEvents>) {

    /**
     * @hidden
     */
    public static uuid = '6e400001-b5a3-f393-e0a9-e50e24dcca9e';

    /**
     * @hidden
     */
    public static async create(service: BluetoothRemoteGATTService): Promise<UartService> {
        const bluetoothService = new UartService(service);
        await bluetoothService.init();
        return bluetoothService;
    }

    private helper: ServiceHelper;

    /**
     * @hidden
     */
    constructor(service: BluetoothRemoteGATTService) {
        super();
        this.helper = new ServiceHelper(service, this);
    }

    private async init() {
        await this.helper.handleListener('receive', UartCharacteristic.tx, this.receiveHandler.bind(this));
        await this.helper.handleListener('receiveText', UartCharacteristic.tx, this.receiveTextHandler.bind(this));
    }

    /**
     * Send serial data
     * @param value The buffer to send
     */
    public async send(value: BufferSource): Promise<void> {
        return this.helper.setCharacteristicValue(UartCharacteristic.rx, value);
    }

    /**
     * Send serial text
     * @param value The text to send
     */
    public async sendText(value: string): Promise<void> {
        const encoder = new TextEncoder();
        const buffer = encoder.encode(value);
        return this.helper.setCharacteristicValue(UartCharacteristic.rx, buffer);
    }

    private receiveHandler(event: Event) {
        const view = (event.target as BluetoothRemoteGATTCharacteristic).value!;
        const value = new Uint8Array(view.buffer);
        this.dispatchEvent('receive', value);
    }

    private receiveTextHandler(event: Event) {
        const view = (event.target as BluetoothRemoteGATTCharacteristic).value!;
        const decoder = new TextDecoder();
        const value = decoder.decode(view.buffer);
        this.dispatchEvent('receiveText', value);
    }
}