The problem with interrupts would be that I don't have a digital interrupt-condition (only analog). As far as I understand, I have to use a second Arduino board that checks for the zero-crossing and sends a digital ON to an digital input of the first Arduino?
Do you know the sample rate of the Arduino Due board? For implementing a current control, I have to know the exact sample rate. Would there be a way to set the sample rate (one complete loop) to, let's say, 10 kHz?