script.js

// /*
// * Webserial basic demo
// */
'use strict';

// Global variables
let port = null; //object
let outputDone;
let outputStream;
let reader;
let inputDone;
let inputStream;

// check if broswer supports webserial
function check_compatability() {
  if ('serial' in navigator) {
    console.log('webserial supported');
    return true
  } else {
    console.log('webserial not supported');
    return false
    }
}



// Disconnect serial connection
async function disconnect() {
  if (reader) { //close input stream
    await reader.cancel();
    await inputDone.catch(() => {});
    reader = null;
    inputDone = null;
  }
  if (outputStream) { //close output stream
    await outputStream.getWriter().close();
    await outputDone;
    outputStream = null;
    outputDone = null;
  }

  await port.close();
  port = null;
  console.log('port closed');

};


// Connect serial port
async function connect() {
  try { //Prompt user to pick serial (COM) port
    port = await navigator.serial.requestPort();
    try { //If successful, proceed to open COM port and enable read & write streams
      await port.open({ 'baudRate': 9600 });
      const encoder = new TextEncoderStream();
      outputDone = encoder.readable.pipeTo(port.writable);
      outputStream = encoder.writable;
      let decoder = new TextDecoderStream();
      inputDone = port.readable.pipeTo(decoder.writable);
      inputStream = decoder.readable;      
      reader = inputStream.getReader();      
      return true;      
    } catch (err) { //Could not open port
      console.error('Error opening port:', err)
    }
  }
  catch (err) { //User closed/cancelled out of prompt
    console.error('User cancelled selection:', err)
  }
  return false;
}

// Write a character to the stream (and the port)
function writeStream(sendString) {
  const writer = outputStream.getWriter();
  console.log('[SENDING]', sendString);
  writer.write(sendString + '\n');
  writer.releaseLock();
}

// Monitor the port for incoming data. Fire off a custom event
// every time a temperature reading is successfully decoded.
async function readLoop() {
  let fullStr = '';
  while (true) {
    const { value, done } = await reader.read();
    if (value) {
      fullStr += value;
      // Could proably just check the last character instead...
      const res = fullStr.match(/(.*)\r\n/);
      if (res) {
        fullStr = ''; 
        emitEvent('readevent', res[1]);
      }
    }
    if (done) {
      console.log('[readLoop] DONE', done);
      reader.releaseLock();
      break;
    }
  }
}