Aranet4 home CO2 device failed pairing, this is how I managed to solve this, YMMV.

• 

  lll_pt

  Posted: 28.05.2026 22:55

  Modified: 07.06.2026 21:10

  I just received today the aranet4 home co2 device.

  I installed the batteries.

  It worked.

  I installed the aranet app.

  And the pairing failed, again and again and again, despite the device being detected.

  The pairing pin appeared on the aranet device, but nothing happened on the app, no message was shown for entering this pin.

  The bluetooth switch was on.

  All the following strategies were tried, all failed the same way, there was no way to enter the pin on the android app.

  I tried this:
  1 - shuttting down the aranet app and retrying the pairing
  2 - erasing the cache, uninstalling and then reinstalling the app
  3 - removing the batteries for 15 minutes, manually changing the switches for bluetooh to off and then to on
  4 - steps 2, 3 and then rebooting the phone

  So I went to Gemini AI and asked for guidance. The suggestion number 3 worked for me:

  "3. Alternative Pairing via Native OS Bluetooth Settings
  If the Aranet application fails to trigger the BluetoothDevice.ACTION_PAIRING_REQUEST broadcast receiver overlay, force the OS layer to handle the pairing sequence directly.
  Ensure the Aranet application is forced closed and not running in the background.
  Open native Android Settings > Connected devices > Pair new device.
  Wait (or manually refresh the list) for the Aranet4 advertisement packet to appear in the scan list. 
  Select the device to force Android's native system dialog to prompt for the 6-digit PIN displayed on the e-ink screen.
  Once paired at the OS level, open the Aranet app to bind the bonded device."

  It worked but I had to select the option "The pin has numbers or letters"

  I went into the app and started again the adding process. It worked. Paired was established. All is good now.

  Gemini expanation for the success:

  "The behavior observed where pairing via native Android settings succeeded, but required a subsequent pairing sequence within the Aranet application, is a consequence of how Android manages Bluetooth Smart (BLE) bonding versus how proprietary applications manage application-layer cryptographic key storage.

  When you completed the step through the native settings, the Android OS established a low-level Security Manager Protocol (SMP) bond, caching the Long Term Key (LTK) at the system level. When you opened the Aranet application, it did not automatically inherit or query this system-level bond table for its local data structure. Instead, the application initiated its own secondary handshake to map the device's hardware address (MAC) to its internal database, syncing the secure application-layer encryption keys necessary to read the environmental sensor characteristics.

  Now that both the Android OS and the Aranet local database recognize the peripheral bond parameters, the connection should remain stable across standard power cycles and background service restarts."

   

  Hope this helps someone with a similar problem.

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