Sonoff Mini flashing ESPHome (OTA v2.0)

gistfile1.txt

Needed software:
- HFS HTTP fileserver (for serving firmware file) - https://www.rejetto.com/hfs/?f=dl
  - Not all HTTP servers will work, it has to support streaming, I think
- Postman (for instructing device to download file from URL) - https://www.postman.com/downloads/

- OTA protocol documentation: https://github.com/itead/Sonoff_Devices_DIY_Tools/blob/master/SONOFF%20DIY%20MODE%20Protocol%20Doc%20v2.0%20Doc.pdf

Steps:
- Prepare your firmware you want to flash (for example from ESPHome)

- Open some packet sniffer to view mDNS packets (in Linux: tcpdump port 5353 -i <your_interface> -vv)
  OR view your router DHCP leases to find you, which IP address your device has
  
- Connect power to device, wait for a while (3-5 seconds)
- Long-press button for 5 seconds (wait till blue LED starts blinking fast)
- Search for WiFi network (with your phone) -> ITEAD-XXXXXXXXXX
  - This part is tricky, be patient and wait for WiFi to appear. Repeat steps above if needed.
- Connect to this itead WiFi - password 12345678
- Open your browser and go to http://10.10.7.1
- Fill in your existing WiFi network (in home for example) and password, Save it.

- Open Postman, send POST request (my device has IP for example 10.36.1.37):
  http://10.36.1.37:8081/zeroconf/info
  ```
  {
  "deviceid": "",
  "data": { }
  }
  ```

- Save returned deviceId (for example 1000f31493)
- You have to unlock OTA mode (have otaUnlock: true in info), so send POST request to 
  http://10.36.1.37:8081/zeroconf/ota_unlock
  ```
  {
  "deviceid": "1000f31493",
  "data": { }
  }
  ```

- Install HFS HTTP Server, start it and drag-n-drop with mouse your firmware file, you want to upload to Sonoff
- Get SHA256 sum of your firmware file - for example with PowerShell:
  Get-FileHash .\firmware_file.bin | Format-List
  
  You have to lowercase this hash! You can use:
  (Get-FileHash .\firmware_file.bin  | select Hash | Select-String Hash).ToString().ToLower()
  
- Send POST request with Postman (change values - device ID, file name, IP of your computer with HFS HTTP server running, sha256sum):
  ```
  {
  "deviceid": "1000f31493",
  "data": {
  "downloadUrl": "http://10.36.1.10/firmware_file.bin",
  "sha256sum":
  "08b2037b519631d8c1440bd35cfdefbd8b0d980496b8c0f55ff9e5d5df667cee"
  }
  }
  ```
  
  You should get a response and will see in HFS HTTP File Server that file is beeing downloaded (Requested GET progress).
  After successful flash, you Sonoff Mini will restart.