meshcore.js/src/connection/web_serial_connection.js

import SerialConnection from './serial_connection.js';

class WebSerialConnection extends SerialConnection {
  constructor(serialPort) {
    super();

    this.serialPort = serialPort;
    this.reader = serialPort.readable.getReader();
    this.writable = serialPort.writable;
    this.readLoop();

    // listen for disconnect
    this.serialPort.addEventListener('disconnect', () => {
      this.onDisconnected();
    });

    // fire connected callback after constructor has returned
    setTimeout(async () => {
      await this.onConnected();
    }, 0);
  }

  static async open() {
    // ensure browser supports web serial
    if (!navigator.serial) {
      alert('Web Serial is not supported in this browser');
      return null;
    }

    // ask user to select device
    const serialPort = await navigator.serial.requestPort({
      filters: [],
    });

    // open port
    await serialPort.open({
      baudRate: 115200,
    });

    return new WebSerialConnection(serialPort);
  }

  async close() {
    // release reader lock
    try {
      this.reader.releaseLock();
    } catch (e) {
      // console.log("failed to release lock on serial port readable, ignoring...", e);
    }

    // close serial port
    try {
      await this.serialPort.close();
    } catch (e) {
      // console.log("failed to close serial port, ignoring...", e);
    }
  }

  /* override */ async write(bytes) {
    const writer = this.writable.getWriter();
    try {
      await writer.write(new Uint8Array(bytes));
    } finally {
      writer.releaseLock();
    }
  }

  async readLoop() {
    try {
      while (true) {
        // read bytes until reader indicates it's done
        const { value, done } = await this.reader.read();
        if (done) {
          break;
        }

        // pass to super class handler
        await this.onDataReceived(value);
      }
    } catch (error) {
      // ignore error if reader was released
      if (error instanceof TypeError) {
        return;
      }

      console.error('Error reading from serial port: ', error);
    } finally {
      this.reader.releaseLock();
    }
  }
}

export default WebSerialConnection;