Using Push Button Switch with PIC Microcontroller

Using Push Button Switch with PIC Microcontroller


I hope that you have already read the first tutorial of Hi Tech C, LED Blinking using PIC Microcontroller. In that tutorial we blink LEDs connected to PORTB by writing to entire PORT and TRIS registers. In some cases we may want to set or reset individual bits of these registers. For that we can use the bit addressable feature of these registers. We have already seen in the previous tutorial that TRIS register is used to set the direction of each bits and PORT register is used to set the status of each bits in a port. A HIGH (1) at a bit of TRIS register makes the corresponding pin input and LOW (0) makes it output. In Hi-Tech C we can use following  methods to write to TRIS and PORT registers.


Writing a Register

TRISB = 0x0F // In binary TRISB = 0b00001111

PORTB = 0xF0 // In binary PORTB = 0b11110000

Writing Bit

TRISB0 = 1 // Makes RB0 a input pin

RB0 = 1 // Makes RB0 HIGH (VDD)

In this tutorial we will define a pin as input and another pin as output. A push button switch is connected to the input pin and the output pin drives an LED. When the switch is pressed, the LED glows for 2 seconds.

Circuit Diagram

Using Push Button Switch - PIC Microcontroller
Using Push Button Switch – PIC Microcontroller

Pin RD0 is defined as an input pin, which is used to connect push button switch and pin RB0 is defined as an output pin, which drives an LED. RD0 is pull up to VDD using a 10KΩ resistor such that when the switch is not pressed the pin will be at the potential VDD and when the switch is pressed it will be grounded. A 470Ω resistor is connected in series with LED to limit the current through it.

Hi-Tech C Code

#include <htc.h>
#define _XTAL_FREQ 8000000
void main()
  TRISD0 = 1; //RD0 as Input PIN
  TRISB0 = 0; //RB0 as Output PIN
  RB0 = 0; //LED OFF
    if(RD0 == 0) //If Switch is presseed
      __delay_ms(100); //Provides required delay
      if(RD0 == 0) //If Switch is still pressed
        RB0 = 1; //LED ON
        __delay_ms(2000); //2 second delay
        RB0 = 0; //LED OFF

I hope that most parts of the above program are explained in its comments. 100ms delay between reading status of switch is provided for following reasons.

  • The above program executes in 8MHz but the time period required for closing and opening the connection of switch varies from 100 – 300ms. Thus a delay must be provided while reading status of a switch. For eg: If you haven’t used delay while reading switch status which is used to counting, it will count multiple times with a single press.
  • It will avoid false triggering by makes sure that the switch is being pressed after a delay.
  • It will provide Switch Debouncing

Download Here

You can download Hi-Tech C files and Proteus files here…

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  • yes, it is working but i am giving the connections RB0 is connected led to ground & RD0 is connect to the directly pull up to VDD & gnd
    thank you sir

  • Greetings, sir. Before I ask, I would like to thank you for all the tutorials you’ve created and posted in this website.

    I have a few question to ask regarding to my circuit in proteus. I’ve constructed the circuit you gave in the picture above. I also built the program using the hitech C compiler using Mplab software. And then, when I try to run the simulation in the proteus using the program i built, it didnt even say error or something like that, instead the led in the circuit itself wont light up. I tried to reinstall all my programming software (mplab, proteus, hitech c). it doesnt work. What should I do. This is really stressing me out. Your tutorials are the only source I have to learn about embedded programming.

    Thank you.

  • hello sir i am using push button and LCD , so my task is how to display on off action of push button on ‘LCD when i press every time
    means for 1 st press it should display on and second press it should display off , cycle repeats
    plz tell me how to write c code for this my mail ID [email protected] Mob No 9028614218

  • hello sir george,i have two questions,i’m newbie in microntrollers, my first question is,if i have asm files what software will i use i will convert to HEX FILES?
    NO.2,If i have HEX files coul i convert it to ASM files?

  • by using 2 push buttons one for incrementing and other for decrementing firing angle of the triac (say in 9 steps one step 10 degrees)…can anybody please help me with code

  • i want to control the firing angle of the triac in ac voltage controller by using a push button,please help me.
    thank you

  • RB0 = 1 // makes 1st bit of portb high.., I think it is false
    the correct is:
    RB1=1, or makes 0st bit of portb high

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