i want to use my arduino board as an ADC for the raspberry to make an digital oscillo !
the signal which is acquired is an alternative sine wave with 50 Hz frequency ,
any help ?
Which arduino board? What sample rate do you want? Total samples fit in RAM?
It makes more sense to me to use an external dedicated ADC - you can easily get higher resolution and higher sampling rates for less cost and less effort than doing this through an Arduino. Mind that the Arduino's ADC can do a mere 9k sps at 10 bit resolution. Good enough for many applications, but for a scope it's pretty sad.
By the way, about USD 200 buys you the DSO Quad from Seeed Studio, I got one and really like it. For a scope it's not fast but it can easily display 1-2 MHz signals which is far more than an Arduino could ever dream of.
I think you need a hat.
Perhaps this one or something similar: https://www.diymat.co.uk/product/universal-plus-hat-raspberry-pi/