Hi Bernd,
I'm not sure really why you have observed this behavior. I downloaded your project and got the same results. However, I changed the code up a bit and now I can succesfully get interrupts using the CSL calls, without going 0->1->0 or 1->0->1.
Please take a look at the attached main.c file. Use the define statements on lines 19 and 20 to choose to test either the falling edge or rising edge.
Thanks,
Ian
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