test6 method

Implementation

Future<void> test6() async {
  const portName = 'COM3'; // <-- change to your port
  log('Available: ${SerialPort.availablePorts}');

  final candidatesBaud = [9600, 19200, 38400, 57600, 115200];
  final candidatesParity = [0, 1, 2]; // none, odd, even
  final candidatesStop = [1, 2];
  final candidatesFlow = [SerialPortFlowControl.none, SerialPortFlowControl.rtsCts, SerialPortFlowControl.xonXoff, SerialPortFlowControl.dtrDsr];

  // Common queries:
  final escposInit = [0x1B, 0x40]; // ESC @
  final escposStat1 = [0x10, 0x04, 0x01]; // DLE EOT 1
  final escposStat2 = [0x10, 0x04, 0x04]; // DLE EOT 4 (paper)
  final zplHS = '~HS\r\n'.codeUnits; // ZPL: printer status
  final zplHelp = '^XA^HH^XZ\r\n'.codeUnits; // ZPL: config/help
  final tsplAuto = 'AUTOBAUD\r\n'.codeUnits; // TSPL: sync baud (some)
  final tsplGet = 'GET STATUS\r\n'.codeUnits; // TSPL: status (varies)

  for (final baud in candidatesBaud) {
    for (final parity in candidatesParity) {
      for (final stop in candidatesStop) {
        for (final flow in candidatesFlow) {
          final port = SerialPort(portName);
          log('\n--- Trying baud=$baud parity=$parity stop=$stop flow=$flow ---');

          if (!port.openReadWrite()) {
            log('openReadWrite() failed: ${SerialPort.lastError}');
            continue;
          }

          final cfg = SerialPortConfig()
            ..baudRate = baud
            ..bits = 8
            ..parity = parity
            ..stopBits = stop
            ..setFlowControl(flow);
          port.config = cfg;

          // Small settle + drain any stale bytes
          await Future<void>.delayed(const Duration(milliseconds: 120));
          await drainSerial(port);

          final tests = <List<int>>[escposInit, escposStat1, escposStat2, zplHS, zplHelp, tsplAuto, tsplGet];

          bool any = false;
          for (final t in tests) {
            final ok = await writeAll(port, t);
            if (!ok) {
              log('write failed');
              break;
            }
            final res = await readUntilQuiet(port);
            if (res.isNotEmpty) {
              any = true;
              log('RESPONSE ${res.length} bytes  hex:[${hex(res)}]  ascii:"${asciiPreview(res)}"');
              log('>>> WORKS with baud=$baud parity=$parity stop=$stop flow=$flow');
              break;
            } else {
              await Future<void>.delayed(const Duration(milliseconds: 120));
            }
          }

          try {
            port.close();
          } catch (_) {}

          if (any) {
            log('\nFound a working configuration above — stop scanning further.');
            return;
          }
        }
      }
    }
  }

  log(
    '\nNo responses on any tried combination.\n'
        '- Check wiring (TX/RX crossed if needed, or use a proper USB-serial)\n'
        '- Confirm device actually replies on serial and which commands\n'
        '- Ensure no other app has the COM port open\n'
        '- Verify exact baud/parity/stop/flow from the printer manual\n',
  );
}