flashing a led

8/3/2019 Flashing a LED

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- AL Azhar University-Gaza

FACULTY OF ENGINEERINGAND INFORMATION TECHNOLOGY

DEPARTMENT OF MECHATRONICS ENGINEERING

Embedded System design

Lab ReportExperment No.One

Prepared by :

MOHAMMED RIYAD AL- NAJJAR

ALI HAMZA MUKAT

Presented to :

Eng. Mohammed Aqel

November 8, 2007First semester, 2007/2008


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Flashing a LED

Objectives: To Understand the Architecture of PIC16F84A

To interface and program the PIC to flash a LED

Introduction:After Studying the architecture of the mid-range microcontroller (PIC16F84A),

we must enhance this knowledge by an experiment, and this experiment is a

simple experiment.

The purpose of this experiment is to make a LED interfaced with PIC16F84A toflash on and off for 1S .

Requirements:Hardware :1) PIC16F84A

2) 4MHz Oscillator

3)2 x 30OF capacitor

4) Resistor 10K

5) Resistor 150

6) LED

Software:1)Proteus

2) PIC Basic compiler

3) MPLAB

4)IC prog

Background :The circuit contains basically the PIC16F84A which won't be run without the

resonator which provides 4MHz frequency and connected to pins OSC1 and

OSC2 with the two 33PF capacitors.

The MCLC pin will be connected to Vdd voltage(+5v) through 10k Pull-up

resistor, this will make the microcontroller to reset and execute the program from

the first instructuion.

The LED will be connected to pin 0 in the port B of the microcontroller thrugh the

150 resistor .As we know, the LED needs a current of 25mA and the PIC can be provide this

current.

All of these will be simulated in the proteus software.


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After connection of the hardware, we will make the LED to light for 1S and then

will off for the same period and so on.

The program will be written in two languages one is low-level language

(assembly) and the other is high-level language(pic basic).This program will be compiled to get the Hex file which will be loaded(burning)

to the PIC using the programmer and the IC prog software and run the circuit .

The Circuit Diagram:The circuit was simulated in proteus software .

The code of program:MPLAB code:

PROCESSOR p16F84A ;Select the processor type#INCLUDE


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__CONFIG _XT_OSC & _PWRTE_ON & _CP_OFF & _WDT_OFF; TO DETERMINE TYPES OF OSCILLATOR.AND WATCHDOG ISOFF

COUNT1 EQU 0XOC ;variablesCOUNT2 EQU 0XODCOUNT3 EQU 0XOE

RESET_VECTOR CODE 0X000GOTO START ;JUMP TO THE START LABEL

INTERRUPT_VECTOR CODE 0X004GOTO INTERRUPT

MAIN CODEINTERRUPTRETFIE

START

BSF STATUS,PR0 ;BANK1CLRF TRISB ;PORTB AS OUTPUTBCF STATUS,RP0 ;BANK0

LOOP BSF PORTB,0 ;LED ONCALL DELAY_1S ;DELAY 1sBCF PORTB,0 ;LED OFFCALL DELLAY_1S ;DELAY 1sGOTO LOOP

DELAY_1s MOVLW .4MOVWF COUNT3 ;MOVE CONSTANT 4 TO

COUNT1

NEXT3 CALL DELAY_250ms ;CALL SUBROYTINEDECFSZ COUNT3,F ;DECREMENT COUNT 3 BY 1

AND JUMP IF ZEROGOTO NEXT3RETURN

DELAY_250ms

MOVLW .250MOVWF COUNT2

NEXT2 CALL DELAY_1ms ;CALL SUBROYTINE


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DECFSZ COUNT2,F ;DECREMENT COUNT 2 BY 1AND JUMP IF ZERO

GOTO NEXT2RETURN

DELAY_1msMOVLW .250MOVWF COUNT1 ;MOVE CONSTANT 250 TO COUNT1

NEXT1NOP ;no operationDECFSZ COUNT1,F ;DECREMENT COUNT1 BY 1

AND

JUMP IF ZEROGOTO NEXT1RETURN

END

PBPro code :Symbol LED = PORTB.0 'Rename pin 0 of port B to LED

TRISB = %11111110 'Setup RB0 as output

main:

High LED 'Set pin 0 of port B high(5 volts) which turns the LED onPause 1000 'Pause 1000 milliseconds with LED on

LOW LED 'Set pin 0 of port B low(0 volts) which turns the LED offPause 1000 'Pause 1000 milliseconds with LED off

GOTO main 'Jump to the main label and do it again

Comments :1)we can make flashing faster or slower simply by changing the pause

or delay.2)The difference is clear between high and low-level language

flashing a led

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