Grumpy_Mike:
This means, in worst case I have killed the module?
Worst case yes but I think it not likely.
What will do your 100R resistor and the zener in detail?
The zener across the input to the module will stop the voltage from rising above the power rail. The resistor will limit the current through the zener and stop the arduino from putting out too much current for the output pin.
Like in this example that uses a zener.
ProtectionI have a friend that I think wired it up directly, let me see if I can contact him and ask. (back soon)
That sounds really good. In the meantime I googled the part of the zener diode. I think the adafruit guys used this level shifter thing.
I will come back later, to see what going on here.
Maybe I will get my module working this evening.
With kind regards