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.

This article is the application of GPIO of PIC18F458 to operate the circuit of 8 LEDs arranged in the same position as the numbers shown in Figure 1 by using 8 LED to be rearranged and called 7-Segment that can be applied to display numbers and another number of characters. In addition, the experimental board has installed a 7-Segment of 4 digits, allowing you to write a program to control the display of 4 digits of data.

After creating the project and basic programming code from the previous article using MPLAB X IDE, this article is the use of a microcontroller to be used as a signal output unit or Output and input signal or Input through the port of PIC18F458 both port A, B, C and D through circuit LED and Switch.

This article uses the MPLAB X IDE development kit (Figure 1) for use with Microchip’s 8-bit microcontrollers in C language through a translation tool called XC8 as a baseline for the next article’s use. The procedure for developing a program with this tool is as follows:

1. Create a project file and set the microcontroller chip type to PIC18F458.
2. Generate a C language file for the XC8 translation Pack.
3. Generate information about microcontroller settings to be pasted into the program code.
4. Compile the program.
5. Bring the resulting file to upload to the board via PICKit2 tool or later.

In the previous article, we introduced the boards used in computer architecture labs and the software used in practice. This time, we will discuss the features and diagrams inside the PIC18F458 from Microchip‘s documentation as a basis for programming the capabilities of the microcontroller in the next article (The details of the PIC16F877 can be read from this article.).