I would like to thank to all of you for the anwers and inputs you provided. It tooks me two days to finally backup a brocken iPhone and I had to combine several of your suggestions, however at the end the backup worked and I got back all the data. Let me explain what I did:
The iPhone screen was broken and my backup was three months old. What a bad luck! And I asked myself why have I not invested the time to establish a backup more frequent? Luckely the home button was still working and every time I started the iPhone the screen was visible for about 5 s. At first I tried to reboot the iPhone which was not a good idea at all, because now the iphone was requesting to type in my passcode! I looked up several blogs in the web and found at the end the following solution.
Tools used
- connector lightning to USB
- USB keyboard
- wireless keyboard
- I connected the USB keyboard to the iPhone using the lightning to USB connector.
- I typed in my passcode to unlock the iPhone, which allowed me to access the phone again!
- I connected my iPhone to my Mac to establish the backup. Unfortunately my iPhone requested me to trust the connection which was not possible due to the brocken screen!
- I unplugged the connection to my Mac, connected again the USB keyboard to access my iPhone.
- I activiated Siri and requested her to turn on voiceover and bluetooth on my iPhone.
- Having voiceover activated, the iPhone told me which app was activated.
- Using my USB keyboard (arrows left/right and alt+ctr+space) I navigated to settings > bluetooth > to connect my wireless keyboard
- Now I connected my iPhone again to my Mac and used the wireless keyboard to finally confirm the connection between my brocken iPhone and my Mac
- I openend iTunes and could sync my iPhone.
I hope that this will help some of you to get access to a broken iPhone.