I use an Arduino mega 2560 and I use it to read digital high (sensor 5v) and LOW 0V
but I ran in to a huge problem, when I use port 30< then it return high even if the port receives 0 volt. When I try to make the following test, read on ex. 52, the it return 1 event i nothning i connected. if I do the same on port 30 i return 0 which i should but when I touch og connect a resistor the i return 1. how can that be? shouldn’t it be possible to read HIGH an LOW on every digital port?
Disconnected inputs will read randomly HIGH or LOW. If you want a pin to read as HIGH when 'not connected to anything' you should use a pull-up resistor, either external or internal (pinMode(x, INPUT_PULLUP);). If you want a pin to read as LOW when 'not connected to anything' you should use an external pull-down resistor.