PIC16F877A GPIO Tutorial

Last Updated on: July 18th, 2022

This article is a continuation of the series of tutorials on the PIC16F877A Microcontroller. The aim of this series is to provide easy and practical examples that anyone can understand. Now we are going to see PIC16F877A LED Interfacing Tutorial (PIC16F877A GPIO Tutorial). If you want to interface with LED, you should know the Registers used for GPIO. At the end of this tutorial, you will be familiar with the PIC GPIO’s and the associated registers for configuring and accessing the GPIO’s.

Prerequisites

• PIC16F877A Introduction

PIC16F877A GPIO Tutorial

Introduction

 PIC16F877A has 33-GPIO‘s grouped into five ports namely PORTA to PORTE. They are used for the input/output interfacing with other devices/circuits. Most of these port pins are multiplexed for handling alternate functions for peripheral features on the devices. All ports in a PIC chip are bi-directional. When the peripheral action is enabled in a pin, it may not be used as its general input/output functions.

• PORTA
• PORTB
• PORTC
• PORTD
• PORTE

Now we will get into GPIO registers.

GPIO Registers

Register	Description
TRISX	This Register is used for Select that respected IO port as a input or output.
PORTX	This is the IO Port

Note: Here ‘x’ could be A,B,C,D,E so on depending on the number of ports supported by the controller.

TRISX Register

Before accessing the PORTX register, we should declare that port whether input or output. So this register is used to select that direction. If you set 0 that IO port will act as the output port. If you set 1 that IO port will act as an input port. Just see the snippet below. Then you will understand.

TRISB = 0xff;  // Configure PORTB as Input.
 
TRISC = 0x00; // Configure PORTC as Output.
 
TRISD = 0x0F; // Configure lower nibble of PORTD as Input and higher nibble as Output
 
TRISD = (1<<0) | (1<3) | (1<<6); // Configure PD0,PD3,PD6 as Input and others as Output

PORTX Register

This register is used to read/write the data from/to port pins. Writing 1’s to PORTx will make the corresponding PORTx pins as HIGH. Similarly writing 0’s to PORTx will make the corresponding PORTx pins as LOW. PORTX registers and their alternate functions are shown in the below table.

PORT	Number of Pins	Alternative Function
PORTA	6 (PA0-PA5)	ADC
PORTB	8 (PB0-PB7)	Interrupts
PORTC	8 (PC0-PC7)	UART,I2C,PWM
PORTD	8 (PD0-PD7)	Parallel Slave Port
PORTE	3 (PE0-PB2)	ADC

I think this is enough to make code. Let’s move into the coding part.

LED Interfacing

Code

In this code, I’ve connected LEDs to Port D.

#include<htc.h>

void delay()
{
    unsigned int a;
    for(a=0;a<10000;a++);
}

void main()
{
    TRISD=0;              //Port D is act as Output
    while(1) {
        PORTD=0xFF;   //Port D ON
        delay();
        PORTD=0x00;   //Port D OFF
        delay();
    }
}

Output

[ Please find the output image Here ]

Switch Interfacing

Code

In this code, Switch is connected to Port D. LEDs are connected to Port B.

#include<htc.h>

#define sw RD0                  //Switch is connected at PORTD.0

void delay()
{
    unsigned int a;
    for(a=0;a<10000;a++);
}

void main()
{
    TRISB=0;               //Port B act as Output
    TRISD=0xff;            //Port D act as Input
    while(1) {
        if(!sw) {
            PORTB=0xff;       //LED ON
        } else 
            PORTB=0;          //LED OFF
    }
}

Output

[ Please find the output image Here ]

In our next tutorial, we will see how to use the Timer in PIC16F877A. And also you can see LCD interfacing with the PIC16F877A.

You can also read the below tutorials.

Linux Device Driver Tutorials	C Programming Tutorials
FreeRTOS Tutorials	NuttX RTOS Tutorials
RTX RTOS Tutorials	Interrupts Basics
I2C Protocol – Part 1 (Basics)	I2C Protocol – Part 2 (Advanced Topics)
STM32 Tutorials	LPC2148 (ARM7) Tutorials
PIC16F877A Tutorials	8051 Tutorials
Unit Testing in C Tutorials	ESP32-IDF Tutorials
Raspberry Pi Tutorials	Embedded Interview Topics
Reset Sequence in ARM Cortex-M4	BLE Basics
VIC and NVIC in ARM	SPI – Serial Peripheral Interface Protocol
STM32F7 Bootloader Tutorials	Raspberry PI Pico Tutorials
STM32F103 Bootloader Tutorials	RT-Thread RTOS Tutorials
Zephyr RTOS Tutorials - STM32	Zephyr RTOS Tutorials - ESP32
AUTOSAR Tutorials	UDS Protocol Tutorials
Product Reviews	STM32 MikroC Bootloader Tutorial
VHDL Tutorials