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 #

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

Print Quality Issues #

• 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.