I did some fault-finding, but cannot resolve the problem. Here is what I did:
I’ve now assembled the motherboard, digitiser and sensorarray. The motherboard and digitiser worked perfectly together and I ran the Digiclock sketch that worked fine. Wiring in accordance with the project idea in the digitiser manual (page 30). I’ve now also assembled the sensorarray and this also seems to work perfectly. I tested it with the sketches from the manual coding basics. The wiring is ‘added’ to the motherboard in accordance with the project idea “data logger”. Additionally I’ve written with your basics a sketch to show the microphone output on the digitiser. It works! Then I reloaded the original Digiclock sketch to have the clock again on my desk. The clock now switches indiscriminately between the different modes and it looks like this is influenced by the microphone. It reacts to sound and turning the pot RV1 changes the sensitivity in which it switches between the modes. When I disconnected the sensorarray (only VCC) the clock works again as supposed to.
I noticed that the wiring of the digitiser and sensorarray connect at the motherboard at D10 and A0. At A0 Switch1 and the microphone come together. As I supposed this to be the problem, I reconnected the sensorarray Mic to A4. The microphone remains working fine with the software change: “const int MIC = A4”. My own sketch to show the microphone values on the digitiser also works. Hooray! I thought to have found the problem.
HOWEVER. Now the RTC seemed to go haywire (none of the RTC sketches work and your sketch to show the date via the Serial Monitor had weird values). Moreover the Digiclock sketch shows no values at all (My sketch to show the microphone on the digitiser still works). So, I returned the connection of Mic back to A0 and I am back were I started. Everything seems to be working fine, accept for the Digiclock sketch that changes modes by microphone input. What I see as another possibility is the common connection to D10, where the digitiser OE and the sensorarray CS come together. I do not understand enough of the boards to comprehend its influence on my problem.