An Android USB Serial Flutter Plugin

This plugin allows Flutter code to interact with USB serial devices connected to your Android device. For example an FTDI or CDC based USB device.

Add a dependency to your pubspec.yaml

dependencies:
	usb_serial: ^0.3.0

include the usbserial package at the top of your dart file.

import 'package:usb_serial/usb_serial.dart'

Edit android\app\build.gradle and add

    compileOptions {
        sourceCompatibility 1.8
        targetCompatibility 1.8
    }

to the 'android' object, see build.grade from the example project for a template on how to do this. Without this you'll get a bunch or Java errors.

Add

	<intent-filter>
		<action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
	</intent-filter>

	<meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
		android:resource="@xml/device_filter" />

to your AndroidManifest.xml

and place device_filter.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!-- 0x0403 / 0x6001: FTDI FT232R UART -->
    <usb-device vendor-id="1027" product-id="24577" />
    
    <!-- 0x0403 / 0x6015: FTDI FT231X -->
    <usb-device vendor-id="1027" product-id="24597" />

    <!-- 0x2341 / Arduino -->
    <usb-device vendor-id="9025" />

    <!-- 0x16C0 / 0x0483: Teensyduino  -->
    <usb-device vendor-id="5824" product-id="1155" />

    <!-- 0x10C4 / 0xEA60: CP210x UART Bridge -->
    <usb-device vendor-id="4292" product-id="60000" />
    
    <!-- 0x067B / 0x2303: Prolific PL2303 -->
    <usb-device vendor-id="1659" product-id="8963" />

    <!-- 0x1366 / 0x0105: Segger JLink -->
    <usb-device vendor-id="4966" product-id="261" />

    <!-- 0x1366 / 0x0105: CH340 JLink -->
    <usb-device vendor-id="1A86" product-id="7523" />

</resources>

in the res/xml directory. This will notify your app when one of the specified devices is plugged in.

...
onPressed: () async {
	List<UsbDevice> devices = await UsbSerial.listDevices();
	print(devices);

	UsbPort port;
	if (devices.length == 0) {
		return;
	}
	port = await devices[0].create();

	bool openResult = await port.open();
	if ( !openResult ) {
		print("Failed to open");
		return;
	}
	
	await port.setDTR(true);
	await port.setRTS(true);

	port.setPortParameters(115200, UsbPort.DATABITS_8,
	  UsbPort.STOPBITS_1, UsbPort.PARITY_NONE);

	// print first result and close port.
	port.inputStream.listen((Uint8List event) {
		print(event);
		port.close();
	});

	await port.write(Uint8List.fromList([0x10, 0x00]));
}
...

This API is a layer on top of the asynchronous part of the library. It provides two Stream Transformers and a Transaction helper based on the StreamQueue class.

1. Terminated Transformer, this splits incoming data based on a configurable end of message bytes "terminator".
2. Magic Header + Length byte, this splits incoming data based on a configurable header ( with wildcards! ) and a length byte directly following the header.

In case neither is a fit, you can use one of those Transformers to create you own that is specific to the binary format you are dealing with.

	
    ...
    Transaction<String> transaction = Transaction.stringTerminated(port.inputStream, Uint8List.fromList([13,10]));
    ...

    // While using transactions you can still listen to all 
    // incoming messages!    
    transaction.stream.listen( (String data) {
      print(data);
    });

    // you can write asynchronous messages as before!
    p.write(Uint8List.fromList([65,66,13,10]));
    
    // BUT you can also write 'transactions'. This is a combination of a flush, write and wait for response
    // with a timeout. If no response is received within the timeout a null value is returned.
    // this sends "AB\r\n"
    var response = await transaction.transaction(p, Uint8List.fromList([65,66,13,10]), Duration(seconds: 1) );
    print("The response was $response");
    

In version 0.3.0 a resource bug was fixed (issue #35) which required signature changes.

The Transformer classes previously inherited directly from StreamTransformer, this class however has no dispose method. So a new abstract class was added to include dispose and called by Transaction.dispose().

abstract class DisposableStreamTransformer<T, R> implements StreamTransformer<T, R> {
  void dispose();
}

Steps:

• Change parent class to DisposableStreamTransformer
• Implement dispose class, and make sure to dispose of your StreamController

The Transaction class previously did not have access to the transformer, only the stream. The signature of Transaction constructor changed from

Transaction<T>(Stream<T>);

to

Transaction(Stream<Uint8List> stream, DisposableStreamTransformer<Uint8List, T> transformer);

If you are using the static factory methods you should not have to make any changes to your code. Only if you created your own Transformer/Transactions.

This library depends on:

https://github.com/felHR85/UsbSerial