This article uses the GPIO of the PIC18F458 microcontroller connected to an ADC module or an analog-to-digital converter module for reading voltage levels in the 0 to 5V range from the input signal. This allows the system designer to consider the details of the voltage from the circuit, such as from the variable resistor, resistors change their values ​​according to the brightness or microphone values, for example, to process these values or enter the next working condition, such as reading the voltage to report the result as a voltage in the Lo, Hi or unstable level, etc. On the computer architecture experiment board, there are 4 sets of adjustable resistor circuits as shown in Figure 1 makes it possible to study programming to use the ADC module and be able to apply it in the future.