In this tutorial we will learn How to Blink an LED with PIC Microcontroller using MPAB XC8 Compiler. Recently Microchip released a series of development tools including MPLAB X IDE and MPAB XC Compilers. MPLAB X IDE is a software that runs on a computer intended to develop applications for Microchip’s Microcontrollers and Digital Signal Controllers. It can be used with Windows, Mac and Linux Operating Systems. It is called an Integrated Development Environment as it provides comprehensive facilities to the developers. Unlike previous  versions of MPLAB, MPLAB X IDE is based on open source NetBeans IDE by Oracle.

MPLAB XC Compilers are general solutions for all Microchip PIC Microcontrollers and it can be used for any Project. It replaces all MPLAB C and Hi-Tech C compilers. Microchip recommends every developers to use MPLAB XC Compilers. These compilers integrates with MPLAB X IDE to provide full graphics front end.

In this example project we will blink an LED using PIC 16F877A Microcontroller. For that we will use MPLAB X IDE and MPLAB XC8 Compiler. You can download MPLAB X IDE and XC8 Compiler from the respective pages.

You should install Java before installing MPLAB X.

• Download and Install MPLAB X IDE.
• Download and Install MPLAB XC8 Compiler.
• Open MPLAB X IDE.

• Click on File >> New Project

• Select Microchip Embedded >> Standalone Project
• Click Next

• Select Family and Device.
• Click Next

• Select your Hardware Tool. Don’t worry if your programmer is not supported. You can directly burn the hex file after building the project.
• Click Next

• Select the Compiler XC8.
• Click Next

• Give Project Name, Project Location etc.
• Click Finish

• Right Click on the Source Files in the Project Tree.

• Select New >> C Main File
• Provide Name and Location of the file

• New Source file is created, you can add code here.

MPLAB XC8 Programming

• Input Outputs pins of a PIC Microcontroller is divided into different PORTS containing a group of GPIO (General Purpose Input Output) pins.
• Since PIC 16F877A is an 8-bit microcontroller, each PORT contains 8 Input Output pins.
• In 16F Microcontrollers, each port is associated with two registers : TRIS and PORT. Eg : TRISB, PORTB, TRISD, PORTD.
• TRIS stands for Tri-State, it determines the direction of each GPIO pins. Logic 1 at a particular bit of TRIS register makes the corresponding pin Input while Logic 0 at a particular bit makes the corresponding pin Output.
• All Input pins will be in Hi-Impedance state.
• PORT Register is used to Read Data from or Write Data to Input Output pins.
• For an Output pin (TRIS bit is 0), Logic 1 at PORT register makes the corresponding pin Logic High (VDD) and Logic 0 at PORT register makes the corresponding pin Logic Low (VSS).
• Since PIC 16F877A is a 5V device, VDD = 5V and VSS = 0V.
• PORT Read operation reads the Physical State (actual Voltage Level) of IO pins. If an IO pin is at a potential near to VDD, corresponding PORT bit will be Logic 1 and if it at a potential near to VSS, corresponding PORT bit will be Logic 0.

Writing Registers

You can write to PORT and TRIS Registers entirely or bit by bit.

Writing Bit by Bit :

TRISC0 = 1; //Makes 0th bit of PORTC Input
TRISC5 = 0; //Makes 5th bit of PORTC Output
RB3 = 1; //Makes 3ed bit of PORTB at Logic High
RB7 = 0; //Makes 7th bit of PORTB at Logic Low

Writing Entire Register

You should be familiar with following C Programming concepts.

• A number with a prefix ‘0b’ indicates a binary number.
• A number with a prefix ‘0’ indicates an octal number.
• A number with a prefix ‘0x’ indicates a hexadecimal number.
• A number without prefix is a decimal number.

Let’s see some examples…

PORTB = 0xFF; //Makes all pins of PORTB Logic High
TRISC = 0x00; //Makes all pins of TRISC Output
PORTD = 128; //Makes 7th bit of PORTD Logic High

Code – LED Blinking

#define _XTAL_FREQ 8000000

#include <xc.h>

// BEGIN CONFIG
#pragma config FOSC = HS // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = ON // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
//END CONFIG

int main()
{
  TRISB0 = 0; //RB0 as Output PIN
  while(1)
  {
    RB0 = 1;  // LED ON
    __delay_ms(1000); // 1 Second Delay
    RB0 = 0;  // LED OFF
    __delay_ms(1000); // 1 Second Delay
  }
  return 0;
}

First statement #define _XTAL_FREQ 8000000 defines the clock frequency of the microcontroller which is used to calculate delays in __delay_ms() function. Second statement #include <xc.h> includes the header file xc.h which contains the definition of __delay_ms() function and TRIS, PORT registers.

Next is #pragma config directives, which is used to tell the compiler to set Configuration Bits of PIC Microcontroller. You can generate it using the MPLAB IDE as following.

• Go to Window >> PIC Memory Views >> Configuration Bits

• You can select the configuration at the bottom of the IDE as shown below

• Click Generate Source Code to Output

• You can simple copy paste this generated code to code editor.
• Then enter the remaining code for the blinking of LED.
• Build the Project

• Hex File will be generated in the location Your Project Folder >> dist >> default >> production

Circuit Diagram

VDD and VSS of the PIC Microcontroller is connected to +5V and GND respectively. 8MHz crystal oscillator is used to provide necessary clock for the operation of the microcontroller. 22pF capacitors are used to stabilize the clock generated by crystal oscillator. An LED is connected to RBO (Pin 33) via a 470Ω resistor to limit the current.

Download Here

You can download entire project files here…

• Getting Started – LED Blinking