iOS: No notifications from notify-only characteristic (FFF2) and reader beep doesn’t trigger on ACS ACR1255U-J1 (BLE)/ ACR1311U-N2 after connect

[cmtanko]

I am able to connect with the NFC reader, but cannot make it beep nor read any NFC cards.

Environment

• Library version: react-native-ble-plx 3.5.0
• React Native version: 0.72.3"
• Dev machine: macOS 14 (Sonoma)
• Permissions: NSBluetoothAlwaysUsageDescription present in Info.plist
• iOS setup: Followed per react-native-ble-plx iOS example setup

Hardware

• Primary device: ACS ACR1255U-J1 (BLE) — advertised name: ACR1255U-J1-001592
• Also tested: ACS ACR1311U-N2 (BLE)

GATT Profile Discovered

Main Service: 0000fff0-0000-1000-8000-00805f9b34fb

• 0000fff1-... — write (command characteristic)
• 0000fff2-... — notify (response characteristic, notify-only)
• 0000fff3-... — read, notify (varies per unit)

Other services: Generic Device Info (180A) and Battery (180F) read successfully

Expected Behavior

1. After connecting, discovering services, and enabling notifications on FFF2, monitoring should deliver notifications
2. Writing ACS commands to FFF1 should produce responses on FFF2
3. Beep commands should trigger the reader's built-in buzzer

Actual Behavior

• ✅ Connection successful; services and characteristics discovered
• ✅ Successfully read values from 180A and 180F characteristics (BLE session works)
• ❌ Attempts to read FFF2 fail as expected (notify-only characteristic)
• ❌ Monitoring FFF2 produces no notifications
• ❌ Writes to FFF1 "succeed" (both with/without response), but:
  • Reader does not beep
  • No notifications arrive on FFF2

Logs (truncated)

📡 Service 3: 0000fff0-0000-1000-8000-00805f9b34fb
  1. 0000fff1… Properties: write
     ⚠️ Read attempt failed (as expected for write-only)
     ✅ Can write
  2. 0000fff2… Properties: notify
     ⚠️ Read attempt failed (notify-only)
     ✅ Can notify/indicate
  3. 0000fff3… Properties: read, notify
     ⚠️ Read attempt failed (on some runs)
     ✅ Can notify/indicate

NFC Status: 🔐 Authenticating with master key...
NFC Status: ✅ Authentication sent
NFC Status: 🔄 Starting auto-polling...
NFC Status: ✅ Sleep disabled
NFC Status: 🔊 Testing beep...
NFC Status: ✅ Beep sent
NFC Status: ✅ Init complete
NFC Status: 👂 Listening for cards...

Minimal Reproduction (iOS)

Following the documented iOS sequence: connect → discoverAllServicesAndCharacteristics → find FFF1/FFF2 → monitor FFF2 → write to FFF1.

// 1. Connect and discover
const device = await manager.connectToDevice(id, { autoConnect: false });
await device.discoverAllServicesAndCharacteristics();

// 2. Resolve FFF1 (write) and FFF2 (notify) from FFF0 service
const services = await device.services();
const fff0 = services.find(s => s.uuid.toLowerCase().includes('fff0'));
const chars = await fff0.characteristics();
const cmd = chars.find(c => c.uuid.toLowerCase().includes('fff1')); // write
const rsp = chars.find(c => c.uuid.toLowerCase().includes('fff2')); // notify

// 3. Start monitoring FFF2 BEFORE any writes
const sub = rsp.monitor((error, ch) => {
  if (error) {
    console.log('Monitor error:', error);
    return;
  }
  if (ch?.value) {
    console.log('📥 Notification received:', ch.value);
    // ❌ This never fires for us
  }
});

// 4. Helper function to send commands
const send = async (bytes) => {
  const b64 = bytesToBase64(bytes);
  try {
    await cmd.writeWithResponse(b64);
  } catch {
    await cmd.writeWithoutResponse(b64);
  }
};

// 5. Typical ACS initialization + beep sequence
await send([0xE0, 0x00, 0x00, 0x48, 0x00]);       // Disable sleep (escape)
await send([0xE0, 0x00, 0x00, 0x40, 0x01]);       // Auto poll ON (escape)
await send([0xE0, 0x00, 0x00, 0x28, 0x01, 0x50]); // Long beep (escape)

// 6. Then Get UID (APDU)
await send([0xFF, 0xCA, 0x00, 0x00, 0x00]);       // Expect notification on FFF2
                                                   // ❌ Never arrives

[Tclha]

Did you ever figure this out? I'm having this issue in a particular situation, while the rest of my command/response cycles work fine, and I cannot figure it out. (Android)

[cmtanko]

@telha for Android, I am using this package https://www.npmjs.com/package/react-native-acs-reader . But not able to make it work for iOS