flutter_sewoo_usb_printer

A Flutter plugin for Sewoo POS printers using USB/Serial connection. This plugin provides a comprehensive wrapper around the Sewoo Android SDK 1.114 library for USB connectivity.

Features

  • USB Serial Connection: Auto-detect and connect to USB serial ports
  • Text Printing: Multiple fonts, sizes, and alignments
  • Barcode Support: CODE39, CODE128, EAN8/13, UPC-A/E, ITF, CODABAR
  • QR Code: Configurable size and error correction levels
  • Image & PDF Printing: Direct printing from bytes or file paths
  • Status Monitoring: Real-time printer status via ASB mode
  • ESC/POS Commands: Full raw command support
  • Multi-encoding: UTF-8, EUC-KR, BIG5, GB2312, Shift_JIS
  • Cash Drawer Control: Open command support

Installation

Add to your pubspec.yaml:

dependencies:
  flutter_sewoo_usb_printer: ^0.0.1

Android Configuration

Add permissions to AndroidManifest.xml:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

For Android 10+ (API 29+):

<application android:requestLegacyExternalStorage="true">

Quick Start

import 'package:flutter_sewoo_usb_printer/flutter_sewoo_usb_printer.dart';

// Get available ports
List<String> ports = await FlutterSewooUsbPrinter.getAvailablePorts();

// Connect to printer
bool connected = await FlutterSewooUsbPrinter.connect(
  ports.first,
  baudRate: 9600, // 9600, 19200, 38400, 57600, 115200
);

// Print text
await FlutterSewooUsbPrinter.printText(
  'Hello World',
  alignment: FlutterSewooUsbPrinter.ALIGN_CENTER,
  fontType: FlutterSewooUsbPrinter.FONT_BOLD,
  textSize: FlutterSewooUsbPrinter.TEXT_SIZE_2X,
);

// Print barcode
await FlutterSewooUsbPrinter.printBarcode(
  '1234567890',
  barcodeType: FlutterSewooUsbPrinter.BARCODE_CODE128,
  height: 100,
  width: 2,
  alignment: FlutterSewooUsbPrinter.ALIGN_CENTER,
  hriPosition: FlutterSewooUsbPrinter.HRI_TEXT_BELOW,
);

// Print QR code
await FlutterSewooUsbPrinter.printQRCode(
  'https://example.com',
  moduleSize: 6,
  errorLevel: FlutterSewooUsbPrinter.QR_ERROR_LEVEL_M,
);

// Cut paper and disconnect
await FlutterSewooUsbPrinter.cutPaper();
await FlutterSewooUsbPrinter.disconnect();

Core Methods

Connection Management

// Get available USB serial ports
List<String> ports = await FlutterSewooUsbPrinter.getAvailablePorts();

// Connect to printer
bool connected = await FlutterSewooUsbPrinter.connect(portName, baudRate: 9600);

// Check connection status
bool isConnected = await FlutterSewooUsbPrinter.isConnected();

// Get connection info
Map<String, dynamic> info = await FlutterSewooUsbPrinter.getConnectionInfo();

// Disconnect
await FlutterSewooUsbPrinter.disconnect();

Text Printing

// Print formatted text
await FlutterSewooUsbPrinter.printText(
  text,
  alignment: FlutterSewooUsbPrinter.ALIGN_CENTER,    // LEFT, CENTER, RIGHT
  fontType: FlutterSewooUsbPrinter.FONT_BOLD,       // DEFAULT, BOLD, UNDERLINE, REVERSE
  textSize: FlutterSewooUsbPrinter.TEXT_SIZE_2X,    // 1X, 2X, 3X, 4X
);

// Print raw string
await FlutterSewooUsbPrinter.printString('Simple text\n');

// Print with Android fonts
await FlutterSewooUsbPrinter.printAndroidFont(
  text,
  fontFamily: 'monospace',
  fontSize: 24,
  alignment: FlutterSewooUsbPrinter.ALIGN_LEFT,
);

Barcode & QR Code

// Print barcode
await FlutterSewooUsbPrinter.printBarcode(
  data,
  barcodeType: FlutterSewooUsbPrinter.BARCODE_CODE128,
  height: 100,
  width: 2,
  alignment: FlutterSewooUsbPrinter.ALIGN_CENTER,
  hriPosition: FlutterSewooUsbPrinter.HRI_TEXT_BELOW,
);

// Print QR code
await FlutterSewooUsbPrinter.printQRCode(
  data,
  moduleSize: 6,  // 1-16
  errorLevel: FlutterSewooUsbPrinter.QR_ERROR_LEVEL_M,  // L, M, Q, H
);

Image & PDF Printing

// Print image from bytes
Uint8List imageData = // ... your image data
await FlutterSewooUsbPrinter.printImage(imageData);

// Print image from file
await FlutterSewooUsbPrinter.printImageFile('/path/to/image.png');

// Print PDF page
await FlutterSewooUsbPrinter.printPDF(
  '/path/to/document.pdf',
  pageNumber: 0,  // 0-based index
);

Printer Control

// Line feed
await FlutterSewooUsbPrinter.lineFeed(lines: 3);

// Cut paper
await FlutterSewooUsbPrinter.cutPaper();

// Open cash drawer
await FlutterSewooUsbPrinter.openCashDrawer();

// Reset printer
await FlutterSewooUsbPrinter.reset();

// Send raw ESC/POS commands
await FlutterSewooUsbPrinter.sendRawData(Uint8List.fromList([0x1B, 0x40]));

Status Monitoring

// Check status once
PrinterStatus status = await FlutterSewooUsbPrinter.checkPrinterStatus();
if (status.isPaperEmpty) {
  print('Paper is empty!');
}

// Enable real-time monitoring
await FlutterSewooUsbPrinter.enableASBMode(true);

// Listen to status updates
FlutterSewooUsbPrinter.getStatusStream().listen((status) {
  if (status.isError) {
    print('Error: ${status.errorMessage}');
  }
});

PrinterStatus Object

class PrinterStatus {
  final int statusCode;        // Raw status code
  final bool isNormal;         // Printer ready
  final bool isPaperEmpty;     // No paper
  final bool isPaperNearEnd;   // Low paper
  final bool isCoverOpen;      // Cover open
  final bool isError;          // Error state
  final bool isCashDrawerOpen; // Drawer open
  final String? errorMessage;  // Error details
}

Constants Reference

Alignment

  • ALIGN_LEFT - Left alignment
  • ALIGN_CENTER - Center alignment
  • ALIGN_RIGHT - Right alignment

Font Types

  • FONT_DEFAULT - Normal font
  • FONT_BOLD - Bold font
  • FONT_UNDERLINE - Underlined text
  • FONT_REVERSE - Reverse video

Text Sizes

  • TEXT_SIZE_1X - Normal size
  • TEXT_SIZE_2X - Double size
  • TEXT_SIZE_3X - Triple size
  • TEXT_SIZE_4X - Quadruple size

Barcode Types

  • BARCODE_CODE39, BARCODE_CODE128
  • BARCODE_EAN8, BARCODE_EAN13
  • BARCODE_UPC_A, BARCODE_UPC_E
  • BARCODE_ITF, BARCODE_CODABAR

HRI Positions

  • HRI_TEXT_NONE - No text
  • HRI_TEXT_ABOVE - Above barcode
  • HRI_TEXT_BELOW - Below barcode
  • HRI_TEXT_BOTH - Both positions

QR Error Levels

  • QR_ERROR_LEVEL_L - Low (7%)
  • QR_ERROR_LEVEL_M - Medium (15%)
  • QR_ERROR_LEVEL_Q - Quartile (25%)
  • QR_ERROR_LEVEL_H - High (30%)

Error Handling

try {
  await FlutterSewooUsbPrinter.connect('/dev/ttyUSB0');
} catch (e) {
  if (e is FlutterSewooException) {
    print('Error: ${e.message}');
  }
}

Supported Encodings

// Set encoding for text printing
await FlutterSewooUsbPrinter.setEncoding('EUC-KR');

Available encodings:

  • UTF-8 (default)
  • EUC-KR (Korean)
  • BIG5 (Traditional Chinese)
  • GB2312 (Simplified Chinese)
  • Shift_JIS (Japanese)

Example App

Complete example available in the example folder:

cd example
flutter run

Platform Support

Platform Support
Android ✅ (Min SDK 21)
iOS ❌
Web ❌
Windows ❌
macOS ❌
Linux ❌

Requirements

  • Android device with USB OTG support
  • USB to Serial adapter (if needed)
  • Sewoo POS printer compatible with SDK 1.114
  • Flutter 2.5.0+
  • Dart 2.12.0+

Troubleshooting

No Ports Detected

  • Ensure USB cable is properly connected
  • Check USB debugging is enabled
  • Verify printer is powered on
  • Try different USB ports/cables

Connection Failed

  • Verify correct baud rate (usually 9600 or 115200)
  • Ensure no other app is using the port
  • Check port name is correct
  • Try reconnecting USB cable
  • Check paper quality
  • Clean printer head
  • Ensure proper power supply

ASB Mode Not Working

  • Not all models support ASB
  • Update printer firmware
  • Try lower baud rates

License

MIT License - see LICENSE file

Contributing

Contributions welcome! Please submit a Pull Request.

Support

For issues or questions, please file an issue on GitHub.

Acknowledgments

Based on Sewoo Android SDK 1.114.

Libraries

flutter_sewoo_usb_printer