When you use a smaller Arduino, like Pro Mini, you can run it on 3.3V, perfect for connecting it directly to a RasPi. And when you let it sleep until a button is pressed, it will consume only a few µA.
When you use a smaller Arduino, like Pro Mini, you can run it on 3.3V, perfect for connecting it directly to a RasPi. And when you let it sleep until a button is pressed, it will consume only a few µA.