esp-homekit-sonoff-mini

Homekit firmware for Sonoff mini

You can wire a switch across S1 & S2, this is NOT 240V, it is only ESP8266 signal level and does not require a particularly heavy gauge of wire.

Tested in UK dry lining wall box, tight fit but works ok.

12th April 2022 - New capability added to preserve the power state over a power outage. By default the state will not be preserved, if you want to change the default to preserve the state then using Eve app set "Preserve State" to "On".

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Factory Reset (Remote, Password-Protected)

The firmware supports a secure remote factory reset via UDP on port 9876. This is useful if you lose physical access to the device or need to reset it without button presses.

How It Works

1. Set a password via HomeKit (Eve app or any HomeKit app that exposes custom characteristics):

   • Find the "Set Factory Reset Password" characteristic in the Switch service
   • Enter a password (e.g., MySecret123)
   • The password is stored once and cannot be changed without a full reflash

2. Trigger factory reset by sending a UDP packet:

   printf "FACTORY_RESET YourPasswordHere" | nc -u -w1 <device-ip> 9876

   • Replace YourPasswordHere with the password you set
   • Replace <device-ip> with the Sonoff Mini's IP address
   • Use printf (not echo) to avoid trailing newlines

3. What happens:

   • Device validates the password
   • Sets ota_count=14 in sysparam
   • Reboots into LCM (Life Cycle Manager) OTA mode
   • LCM erases all user config, WiFi credentials, and HomeKit pairings
   • Device boots into AP mode ready for fresh setup

Security Notes

• Password is write-once (cannot be changed without reflashing)
• UDP is not encrypted - use on trusted networks only
• No rate limiting - protect with network segmentation if needed
• Password stored as FRPW:YourPassword in ota_string sysparam

Debugging

Enable verbose logging (log level 7 via HomeKit) to see:

fr_recv_callback: packet received from 192.168.1.X:XXXXX, len=XX
fr_recv_callback: payload='FACTORY_RESET YourPassword'
fr_recv_callback: searching for password 'YourPassword' (len=XX)
fr_recv_callback: found stored ota_string='FRPW:YourPassword'
fr_recv_callback: actual_fr_pw='YourPassword' (len=XX)
fr_recv_callback: PASSWORD MATCH! Executing factory reset!

Example

# Set password in Eve app first, then:
printf "FACTORY_RESET MySecret123" | nc -u -w1 192.168.1.208 9876