Hardware flow control not working on Mac in 9.0.7

[ChristiaanWillemsen]

Summary of Problem

(Please answer all 3)

• What are you trying to do?

Open and use a port using rtscts: true

• What happens?

It opens the port, writing data does not seem to work, even when calling drain, the drain event is never called

• What should have happened?

It should've worked ;) Any terminal works just fine (Coolterm for instance)

Code to Reproduce the Issue

export class Modem {
  portName: String;
  port: SerialPort;
  parser: any;
  acceptOpen: () => void | null = null;
  constructor(portName: string) {
    this.portName = portName;
    logger.info(`Starting port ${this.portName}..`);
    this.port = new SerialPort(portName, {
      baudRate: 115200,
      rtscts: true
    }, (err) => {
      this.port.set({ cts: true })
    });
    
  
    this.port.on("data", (buffer:Buffer) => {
      logger.info(`Serial data ${buffer.toString()}`)
    })
    this.port.on("error", (err) => {
      logger.info(`Serial err ${err}`)
    })
    this.port.on("drain", () => {
      logger.info(`Serial drained`)
    })
    this.port.on("open", () => {
      logger.info("Port opened");
      this.port.flush();
      if (this.acceptOpen!=null) {
        this.acceptOpen();
      }
    });
    
    /*this.parser = this.port.pipe(new Readline({ delimiter: '\r\n' }));
    this.parser.on("data", (line) => {
      logger.info("Serial data: " + line);
    });*/
  }

  async open(): Promise<void>{
    logger.info(`Opening port ${this.portName}`)
    if (this.port.isOpen) {
      Promise.resolve();
    } else {
      return new Promise((accept, reject) => {
        this.port.open(() => {});
        this.acceptOpen = accept;
      })
    }
  }

  isOpen(): boolean {
    return this.port.isOpen;
  }

  async doCommand(command: string): Promise<string> {
    logger.info(`Execute moden command [${command}]`)
    return new Promise<string>((accept, reject) => {
      this.port.write(command+"\r\n" ,"ascii");
      this.port.drain((err) => {
        if (err) {
          logger.error("Error writing data" + err);
          reject(err);
        }
      });
      accept("OK");
    })
  }

  static listPorts(): Promise<string[]>{
    return SerialPort.list().then((ports) => ports.map(p => p.path));
  }

}

const modem = new Modem("/dev/tty.usbserial-xxxx");

(async () => {
  await modem.open();
  const res = await modem.doCommand("AT");
  logger.info(res);
  // function body
})()

The "data" event is never called, nor the "drain"

Versions, Operating System and Hardware

• SerialPort@? 9.0.7 and 8.0.8
• Node.js v? v14.15.4, v10.15.3
• MacOS 11.2.1
• Hardware and chipset? (Prolific/FTDI/Other) "Silicon Laboratories, Inc. CP2102N USB to UART Bridge Controller"

[stale]

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