对串行端口执行读写操作

if ("serial" in navigator) {   // The Web Serial API is supported. } 

document.querySelector('button').addEventListener('click', async () => {   // Prompt user to select any serial port.   const port = await navigator.serial.requestPort(); }); 

// Get all serial ports the user has previously granted the website access to. const ports = await navigator.serial.getPorts(); 

// Filter on devices with the Arduino Uno USB Vendor/Product IDs. const filters = [   { usbVendorId: 0x2341, usbProductId: 0x0043 },   { usbVendorId: 0x2341, usbProductId: 0x0001 } ];  // Prompt user to select an Arduino Uno device. const port = await navigator.serial.requestPort({ filters });  const { usbProductId, usbVendorId } = port.getInfo(); 

// Prompt user to select any serial port. const port = await navigator.serial.requestPort();  // Wait for the serial port to open. await port.open({ baudRate: 9600 }); 

const reader = port.readable.getReader();  // Listen to data coming from the serial device. while (true) {   const { value, done } = await reader.read();   if (done) {     // Allow the serial port to be closed later.     reader.releaseLock();     break;   }   // value is a Uint8Array.   console.log(value); } 

while (port.readable) {   const reader = port.readable.getReader();    try {     while (true) {       const { value, done } = await reader.read();       if (done) {         // Allow the serial port to be closed later.         reader.releaseLock();         break;       }       if (value) {         console.log(value);       }     }   } catch (error) {     // TODO: Handle non-fatal read error.   } } 

const textDecoder = new TextDecoderStream(); const readableStreamClosed = port.readable.pipeTo(textDecoder.writable); const reader = textDecoder.readable.getReader();  // Listen to data coming from the serial device. while (true) {   const { value, done } = await reader.read();   if (done) {     // Allow the serial port to be closed later.     reader.releaseLock();     break;   }   // value is a string.   console.log(value); } 

try {   const reader = port.readable.getReader({ mode: "byob" });   // Call reader.read() to read data into a buffer... } catch (error) {   if (error instanceof TypeError) {     // BYOB readers are not supported.     // Fallback to port.readable.getReader()...   } } 

const bufferSize = 1024; // 1kB let buffer = new ArrayBuffer(bufferSize);  // Set `bufferSize` on open() to at least the size of the buffer. await port.open({ baudRate: 9600, bufferSize });  const reader = port.readable.getReader({ mode: "byob" }); while (true) {   const { value, done } = await reader.read(new Uint8Array(buffer));   if (done) {     break;   }   buffer = value.buffer;   // Handle `value`. } 

async function readInto(reader, buffer) {   let offset = 0;   while (offset < buffer.byteLength) {     const { value, done } = await reader.read(       new Uint8Array(buffer, offset)     );     if (done) {       break;     }     buffer = value.buffer;     offset += value.byteLength;   }   return buffer; }  const reader = port.readable.getReader({ mode: "byob" }); let buffer = new ArrayBuffer(512); // Read the first 512 bytes. buffer = await readInto(reader, buffer); // Then read the next 512 bytes. buffer = await readInto(reader, buffer); 

const writer = port.writable.getWriter();  const data = new Uint8Array([104, 101, 108, 108, 111]); // hello await writer.write(data);   // Allow the serial port to be closed later. writer.releaseLock(); 

const textEncoder = new TextEncoderStream(); const writableStreamClosed = textEncoder.readable.pipeTo(port.writable);  const writer = textEncoder.writable.getWriter();  await writer.write("hello"); 

await port.close(); 

// Without transform streams.  let keepReading = true; let reader;  async function readUntilClosed() {   while (port.readable && keepReading) {     reader = port.readable.getReader();     try {       while (true) {         const { value, done } = await reader.read();         if (done) {           // reader.cancel() has been called.           break;         }         // value is a Uint8Array.         console.log(value);       }     } catch (error) {       // Handle error...     } finally {       // Allow the serial port to be closed later.       reader.releaseLock();     }   }    await port.close(); }  const closedPromise = readUntilClosed();  document.querySelector('button').addEventListener('click', async () => {   // User clicked a button to close the serial port.   keepReading = false;   // Force reader.read() to resolve immediately and subsequently   // call reader.releaseLock() in the loop example above.   reader.cancel();   await closedPromise; }); 

// With transform streams.  const textDecoder = new TextDecoderStream(); const readableStreamClosed = port.readable.pipeTo(textDecoder.writable); const reader = textDecoder.readable.getReader();  // Listen to data coming from the serial device. while (true) {   const { value, done } = await reader.read();   if (done) {     reader.releaseLock();     break;   }   // value is a string.   console.log(value); }  const textEncoder = new TextEncoderStream(); const writableStreamClosed = textEncoder.readable.pipeTo(port.writable);  reader.cancel(); await readableStreamClosed.catch(() => { /* Ignore the error */ });  writer.close(); await writableStreamClosed;  await port.close(); 

navigator.serial.addEventListener("connect", (event) => {   // TODO: Automatically open event.target or warn user a port is available. });  navigator.serial.addEventListener("disconnect", (event) => {   // TODO: Remove |event.target| from the UI.   // If the serial port was opened, a stream error would be observed as well. }); 

// Turn off Serial Break signal. await port.setSignals({ break: false });  // Turn on Data Terminal Ready (DTR) signal. await port.setSignals({ dataTerminalReady: true });  // Turn off Request To Send (RTS) signal. await port.setSignals({ requestToSend: false }); 

const signals = await port.getSignals(); console.log(`Clear To Send:       ${signals.clearToSend}`); console.log(`Data Carrier Detect: ${signals.dataCarrierDetect}`); console.log(`Data Set Ready:      ${signals.dataSetReady}`); console.log(`Ring Indicator:      ${signals.ringIndicator}`); 

class LineBreakTransformer {   constructor() {     // A container for holding stream data until a new line.     this.chunks = "";   }    transform(chunk, controller) {     // Append new chunks to existing chunks.     this.chunks += chunk;     // For each line breaks in chunks, send the parsed lines out.     const lines = this.chunks.split("\r\n");     this.chunks = lines.pop();     lines.forEach((line) => controller.enqueue(line));   }    flush(controller) {     // When the stream is closed, flush any remaining chunks out.     controller.enqueue(this.chunks);   } } 

const textDecoder = new TextDecoderStream(); const readableStreamClosed = port.readable.pipeTo(textDecoder.writable); const reader = textDecoder.readable   .pipeThrough(new TransformStream(new LineBreakTransformer()))   .getReader(); 

const [appReadable, devReadable] = port.readable.tee();  // You may want to update UI with incoming data from appReadable // and log incoming data in JS console for inspection from devReadable. 

// Voluntarily revoke access to this serial port. await port.forget(); 

if ("serial" in navigator && "forget" in SerialPort.prototype) {   // forget() is supported. }