# Switch firmware and recover over USB

> Reinstall an unreachable Serin Controller, switch firmware families, or recover from crash-loop safe mode.

Source: https://serin-labs.com/controller/recovery.html
Last updated: 2026-10-27

Use USB to change firmware families or restore a controller you cannot reach on the network. If the controller works and you only want a newer version, follow [Update firmware](https://serin-labs.com/controller/updates.html).

## Before removing the controller

- [Back up settings](https://serin-labs.com/controller/backups.html) or save the ESPHome YAML if the controller is reachable.
- When switching, [choose your firmware](https://serin-labs.com/controller/firmware.html) and expect to repeat network and app setup.

Warning

**Switch off power at the breaker before opening the indoor unit.** Disconnect CN105 before connecting USB. USB must be the controller's only power source during flashing.

## Reinstall, erase settings, or change firmware

1. With power off at the breaker, disconnect CN105. Connect the controller to a computer with a USB-C data cable.
2. Open the [firmware flasher](https://serin-labs.com/flash.html) in Chrome, Edge, or Brave.
3. Choose the firmware and review the warnings before installing:
    - **Reinstall ESPHome:** The version supplied by the flash tool resets stored settings even when **Erase everything first** is unchecked. The install button says **Reset and install**.
    - **Update HomeKit-compatible or Matter-compatible firmware:** Leave **Erase everything first** unchecked to preserve settings, unless the flash tool shows a reset warning for the selected build.
    - **Erase all settings:** Select **Erase everything first** to clear the controller’s flash memory, including saved Wi-Fi details and pairings, before installing any firmware.
4. Install and wait for completion. After an installation that resets settings, configure Wi-Fi and pairing again using the appropriate [setup guide](https://serin-labs.com/documentation.html).
5. Disconnect USB before reconnecting CN105, with HVAC power still off. Follow [physical installation](https://serin-labs.com/controller/install.html), restore power, and verify control.

## Crash-loop safe mode

HomeKit-compatible safe mode keeps only Wi-Fi and the web interface running. Use the IP address from your router; `.local` does not work. The page shows a safe-mode banner. [Update over Wi-Fi](https://serin-labs.com/controller/updates.html#wifi-update) or use USB recovery above.

On Matter-compatible firmware, safe mode offers only the backup setup network and cannot install an update over Wi-Fi. Reinstall the firmware over USB.

See [status lights](https://serin-labs.com/controller/status-lights.html) for the yellow safe-mode pulse.

## If recovery does not solve the problem

If USB cannot detect the controller, follow [USB troubleshooting](https://serin-labs.com/troubleshooting.html#usb-not-detected). If safe mode returns after reinstalling, check wiring and power, then [collect diagnostics](https://serin-labs.com/controller/support-info.html) and [contact support](https://serin-labs.com/contact.html).