serial_port_win32 #

A SerialPort library using win32 API.

Getting Started #

Get Ports #

final ports = SerialPort.getAvailablePorts();
print(ports);
/// result like [COM3, COM4]

Get Ports with more messages (Experimental) #

final List<PortInfo> ports = SerialPort.getPortsWithFullMessages();
print(ports); 
/// print [Port Name: COM3, FriendlyName: 蓝牙链接上的标准串行 (COM3), hardwareID: BTHENUM\{00001101-0000-1000-8000-00803f9b55fb}_LOCALMFG&0000, manufactureName: Microsoft]
PortInfo({
required this.portName,
required this.friendlyName,
required this.hardwareID,
required this.manufactureName,
});

Create Serial Port Instance #

The port instance is Singleton Pattern. Don't re-create port for same Com name.

final port = SerialPort("COM5", openNow: true, ByteSize: 8);
// port.open()
port.openWithSettings(BaudRate: CBR_115200);
// final port = SerialPort("COM5"); /// auto open with default settings

Set parameters #

port.BaudRate = CBR_115200;
port.ByteSize = 8;
port.StopBits = ONESTOPBIT;
port.Parity = NOPARITY;
port.ReadIntervalTimeout = 10;
/// and so on, parameters like win32.

Read #

There are several methods to read bytes from serial port.

• readBytesUntil
  • [readBytesUntil] will read until an [expected] sequence is found
• readBytes
  • General Read with the timeout parameter.
• readFixedSizeBytes
  • [readFixedSizeBytes] will always read until readData.length == bytesSize.

print(await port.readBytesUntil(Uint8List.fromList("T".codeUnits))); /// '\0' is not included
/// or
var read = port.readBytes(18, timeout: Duration(milliseconds: 10))..then((onValue) => print(onValue));
var result = await read;
print(result);
/// or
var fixedBytesRead = port.readFixedSizeBytes(2)..then((onValue) => print(onValue));
await fixedBytesRead;
/// see more in small example

Write #

Write String

String buffer = "hello";
await port.writeBytesFromString(buffer, includeZeroTerminator: false, stringConverter: StringConverter.nativeUtf8);

Write Uint8List

final uint8_data = Uint8List.fromList([1, 2, 3, 4, 5, 6]);
print(await port.writeBytesFromUint8List(uint8_data));

Get Port Connection Status #

port.isOpened == false;

Flow Control #

port.setFlowControlSignal(SerialPort.SETDTR);
port.setFlowControlSignal(SerialPort.CLRDTR);

Close Serial Port #

Close Without Listen

port.close();

Close On Listen

port.closeOnListen(
  onListen: () => print(port.isOpened),
)
  ..onError((err) {
    print(err);
  })
  ..onDone(() {
    print("is closed");
    print(port.isOpened);
  });

Attention #

If you want to read or write strings using serial, be careful to handle the terminator at the end.

Although in most cases, like "Hello\0" (68 65 6C 6C 6F 00) and "Hello"(68 65 6C 6C 6F) both can be identified by computer.

Small Example #

import 'package:serial_port_win32/src/serial_port.dart';

void main() {
    var ports = SerialPort.getAvailablePorts();
    print(ports);
    if(ports.isNotEmpty){
      var port = SerialPort(ports[0]);
      port.BaudRate = CBR_115200;
      port.StopBits = ONESTOPBIT;
      port.close();
    }
}

void _send() async {
  if (!port.isOpened) {
    port.open();
  }

  print('⬇---------------------------- general read (read <=  18 bytes)');
  await port.writeBytesFromString("😄我AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);
  var read = port.readBytes(18, timeout: Duration(milliseconds: 10))
    ..then((onValue) => print(onValue));
  await Future.delayed(Duration(milliseconds: 5));
  await port.writeBytesFromString("😄我AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);
  Uint8List readUint8List = await read;
  print('await result: $readUint8List');

  print('⬇---------------------------- time out read,try to read **18 bytes** data in queue (read <= 18 bytes)');
  await port.writeBytesFromString("😄AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);
  var timeOutRead = port.readBytes(18, timeout: Duration(milliseconds: 10))
    ..then((onValue) => print(onValue));
  await port.writeBytesFromString("😄我AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);

  await timeOutRead;

  print('⬇---------------------------- read successful without timeout, but you just want 8 bytes (read <= 8 bytes)');
  await port.writeBytesFromString("😄AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);
  var wantedBytesRead = port.readBytes(8, timeout: Duration(milliseconds: 10))
    ..then((onValue) => print(onValue));
  await port.writeBytesFromString("😄我AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);

  await wantedBytesRead;

  print('⬇---------------------------- read until specified fixed size (2 bytes), it may cause deadlock (read == 2 bytes)');
  await port.writeBytesFromString("😄AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);
  var fixedBytesRead = port.readFixedSizeBytes(2)
    ..then((onValue) => print(onValue));
  await port.writeBytesFromString("😄我AT",
      includeZeroTerminator: false,
      stringConverter: StringConverter.nativeUtf8);

  await fixedBytesRead;

  port.close();
}

Tested Ciruit #

The code is tested by a UART-USB Conveter. TX and RX are connected together for local loopback.