Input from ports

Now i got respont at input port. In my pcb there are two ports
mentioned as RXD ( PD5 ) & CTS ( PC7 ). i have increase the voltage
from 1.5 v to 3 volt. On LCD Screen by default it shows the port’s
value as 1 but when i pass 3 volt to them it changes to 0. Now even
when i will give 5 V it will show me same result. So here comes new
doubt. How to convert this digital single in to analogue signal(volt) ?
does it need assembly code for converstion ?


You can not connect an analog signal to a digital input. PD5 and PC7 are digital inputs. Assembly code will not help. You need an analog to digital convertor.