[francois.leprieur]

Hello,
I want to make the low pass filter in referring me to the wiki. I see that the inputs and outputs of the ATtiny are connected to GPIO of raspberry through resistors 1 Kohm . Why not use level converters 3.3v <-> 5V GPIO to protect and apply the correct levels on ATtiny ?
thank you in advance for your answers
Best regards

[curlymo]

Because it works fine and safe the way we documented it.

[woutput]

I agree that it works, but I think it is not safe and not the correct way to convert levels. Running the ATTiny on 3V3 is the best solution I think.
@curlymo didn't you report problems running the ATTiny at 3V3?
According to the datasheet it should run down to 1V8 (if I remember correctly)

[curlymo]

Yes, running it on lower voltages can make the tiny less accurate frequency wise. We are running it on it's top frequency. 5v with resistors is safe.