From ST2205u wiki

On my device (Pixika Digital Photo Frame) holding left+enter while doing reset (at the back of the device) Make the device enter in test mode It displays :

  • white, red, green, blue screen
  • lines to see defects on screen
  • software version
  • then it enters in key press mode

=> then left+right make the device swith off, you have to do reset again to switch it on...