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How to Set Up a Timer in PIC16F877A

We have Three Timers in PIC16F877A , and here we have a look to how to setup the TIMER0 in PIC16F877A using HiTech C programm

• To set up the timer, one must first disable interrupts so that an interrupt doesn’t occur when the timer expires.
• Then, enable the timer and assign the prescaler to the timer.
• Establish the prescaler value, and finally, load the timer register.

Whenever the timer expires, the T0IF bit in the INTCON register will be set.

• We must clear this bit, reload the timer register, and then execute the code that is to be done at this time.

In code, the setup portion might look something like:

########################## IN ASSEMBLY PROGRAM ###########################

banksel INTCON

bcf INTCON,T0IE ; Mask timer interrupt

banksel OPTION_REG

bcf OPTION_REG,T0CS ; Enable timer

bcf OPTION_REG,PSA ; Prescaler to timer

bcf OPTION_REG,PS2 ; \

bsf OPTION_REG,PS1 ; >- 1:16 prescale

bsf OPTION_REG,PS0 ; /

movlw D’100’ ; Timer will count

movwf TMR0 ; 156 (256-100) counts

######################## IN HITECH C PROGRAM #######################################

OPTION_REG= 0x0F;

TMR0=0x0F;

while(TMR0IF=0);

TMR0IF=0;

##################################################

• Clearly, the individual bits in the option register could all be set with a single store.

• If we didn’t care about the RB0 interrupt, the weak pullups, or the transition of RA4, then instead of five bit manipulations we could have said:

• movlw B’10000011’ ; Set up prescaler and

• movwf OPTION_REG ; timer

The execution loop might look something like:

main:

btfss INTCON,T0IF ; Did timer overflow?

goto main ; No, hang around some more

movlw D’100’ ; Timer will count

movwf TMR0 ; 156 (256-100) counts

bcf INTCON,T0IF ; reset overflow flag

call DoCode ; Execute main code

goto main ; Go back and wait

Using Timers in PIC16F877A

A timer counts pulses of a fixed, known frequency usually the system clock for the processor.Physically, timer is a register whose value is continually increasing to 255, and then it starts all over again: 0, 1, 2, 3,4...255....0,1, 2, 3......etc.

This incrementing is done in the background of everything a microcontroller does.It is up to programmer to think up a way how he will take advantage of this characteristic for his needs.One of the ways is increasing some variable on each timer overflow.

– If we know how much time a timer needs to make one complete round, then multiplying the value of a variable by that time will yield the total amount of elapsed time.

PIC16F877A has 3 timer modules, Timer0,Timer1 and Timer2.The device has three readable and writeable hardware timers that can increment automatically each instruction cycle (if no prescaler is used).All timers can cause an interrupt on overflow, and then restart from zero.

• Timer 0

timer/counter with prescale ,an 8-bit timer with an eight bit prescaler, which can make the timer run 2 to 256 times slower than normal

• Timer 1

timer/counter with prescale a 16-bit timer (two 8-bit registers) with a 1:1 to 1:8 prescaler and some other features. Used by given C code to generate soft timer and sound

• Timer 2

timer only with prescale and postscale , an 8-bit timer with 1:1 to 1:16 prescaler and a 1:1 to 1:16 postscaler It also has a period register.Used by given C code for PWM motor control

Timer 0

8 bit timer/counter with prescaler
Readable and writeable
8-bit software programmable prescaler
Internal or external clock set
Interrupt on overflow from 0xFF to 0x00
Edge Select for external clock

use TMR0 in program in hitech-c MPLAB X

OPTION_REG= 0x0F;

TMR0=0x0F;

while(TMR0IF=0);

TMR0IF=0;

TIMER1

16-bit timer/counter with prescaler
Readable and writeable
1, 2, 4, 8 programmable prescaler
Internal or external clock select
External clock can be syn. or asyn.
Interrupt on overflow
Second crystal permitted

use TMR1 in Hitech C Program

T1CON= 0x0F;

TMR1= 0x0F;

TMR1ON=1;

while(TMR1IF=0);

TMR1IF=0;

TMR1ON=0;

TIMER2

8-bit timer/counter with prescaler and postscaler

• Readable and writeable

• 1,4 or 16 programmable prescaler

• 4-bit programmable postscaler

• Interrupt on overflow

• Output to port pin

Using Timer2 in Hitech C program

T2CON= 0x0F;

TMR2= 0x0F;

TMR2ON=1;

while(TMR2IF=0);

TMR2IF=0;

TMR2ON=0;

AODV routing Protocol simulation using NS2

The Network Simulator (NS-2) is a most widely used network simulator. It has the capabilities to simulate a range of networks including wired and wireless networks. In this tutorial, we present the implementation of Ad Hoc On-Demand Distance Vector (AODV) Protocol in NS-2.This tutorial is targeted to the novice user who wants to understand the implementation of AODV Protocol in NS-2

FILE REFERENCE OF AODV.H

The step by step process happening in AODV network simulation in NS2

1. In the TCL script, when the user configures AODV as a routing protocol by using the command,

$ns node-config -adhocRouting AODV

the pointer moves to the “start” and this “start” moves the pointer to the Command function of AODV protocol.

2. In the Command function, the user can find two timers in the “start”

* btimer.handle((Event*) 0);

* htimer.handle((Event*) 0);

3. Let’s consider the case of htimer, the flow points to HelloTimer::handle(Event*) function and the user can see the following lines:

agent -> sendHello();

double interval = MinHelloInterval + ((MaxHelloInterval - Min-HelloInterval) * Random::uniform());

assert(interval -> = 0);

Scheduler::instance().schedule(this, &intr, interval);

These lines are calling the sendHello() function by setting the appropriate interval of Hello Packets.

4. Now, the pointer is in AODV::sendHello() function and the user can see Scheduler::instance().schedule(target , p, 0.0) which will schedule the packets.

5. In the destination node AODV::recv(Packet*p, Handler*) is called, but actually this is done after the node is receiving a packet.

6. AODV::recv(Packet*p, Handler*) function then calls the recvAODV(p) function.

7. Hence, the flow goes to the AODV::recvAODV(Packet *p) function, which will check different packets types and call the respective function.

8. In this example, flow can go to case

AODVTYPE HELLO:

recvHello(p);

break;

9. Finally, in the recvHello() function, the packet is received.

hope you have got it how to do ...
you can also generate the codes using NSG2

The files related are given below

aodv.cc

aodv.h

simple-wireless.tcl

Displaying a Word or String in an 16x2 LCD with PIC16F877A and MPLAB X

We have seen how to interface an LCD with PIC16F877A . In this we are printing only a letter in the LCD , now we are going to Display a string on the LCD for this following steps are followed

First Create a MPLAB X project as in the steps for Blinking a LED using MPLAB X , PIC16F877A

And check the Interfacing LCD with PIC16F877A in MPLAB X to know how to interface a LCD

Components
1.PIC16F877A micro controller
2. 2x16 LCD Display

we are using the following functions


void delay(unsigned int msec) // Time delay function
void lcd_cmd(unsigned char item) // Function to send command to LCD
void lcd_data(unsigned char item) // Function to send data to LCD
void lcd_data_string(unsigned char *str) // Function to send data to string
void lcd(unsigned char str[10])

To display the string in LCD , just call the below lines in main function

 lcd_cmd(0x01);
  lcd_cmd(0x86);
  lcd("STRING TO DISPLAY");

The functions are defined below

void delay(unsigned int msec) // Time delay function
{
int i,j ;
for(i=0;i<msec;i++)
  for(j=0;j<1275;j++);
}

void lcd_cmd(unsigned char item) // Function to send command to LCD
{
dataport = item;
rs= 0;
rw=0;
en=1;
delay(1);
en=0;
return;
}

void lcd_data(unsigned char item) // Function to send data to LCD
{
dataport = item;
rs= 1;
rw=0;
en=1;
delay(1);
en=0;
return;
}

void lcd_data_string(unsigned char *str) // Function to send data to string
{
int i=0;
while(str[i]!='\0')
{
  lcd_data(str[i]);
  i++;
  //delay(10);
}
return;
}

void lcd(unsigned char str[10])
{
lcd_cmd(0x38);
lcd_cmd(0x0e);
lcd_data_string(str);
}

Counting the number of times pressed of Switch , C program in MPLAB X

In this program we are going to count the number of times a switch pressed,and displaying it on a LCD .. and each time the switch pressed a LED will lighted up.

First create a new project and add a c main file like in the steps for Blinking a LED using MPLAB X , PIC16F877A

Components

1. PIC16F877A micro controller
2. animated LED
3. A toggle switch
4.16x2 LCD display

Steps in the program

1. define the ports for easy usage

Defines the control pins of LCD to the 0th,1st and 2nd pin of PORT D
#define RS RD0
#define RW RD1
#define EN RD2
Defines the data port of the LCD to PORT B
#define DATA PORTC
Defines switch in the 0th pin of PORT C
#define S RC0
Defines LED on the 3rd pin of PORT D
#define L RD3

2. Function declarations .. here we declare 3 functions and all the 3 functions is for LCD

void LCD_CMD(unsigned int value); //This function is pass the LCD commands

void LCD_DAT(unsigned int value); // this is for pass the DATA to the LCD which is to displayed

void LCD_INIT(); //this to initialize the LCD

void delay(); // this is to delay the LCD commands

for more refer the Interfacing LCD with PIC16F877A in MPLAB X

3. next is main function .. in main function we make

PORT C as input where we have connected the switch
PORT D as output where we have connected the LED and control pins of LCD
PORT B as outout where we have connected DATA pins of LCD

TRISC =0x0F;

TRISD =0x00;

TRISB = 0x00;

4. The function LCD_INIT(); is called for initializing the LCD

5. Declared a variable called count, and initialized it to zero

int count;

count=0;

6. we put the LED off

7. now we are going for a infinite loop by

while(1)

{

}

8. In the loop we are checking switch is ON or OFF condition

if the switch is ON ; LED is on and count is incremented by 1 and display the value of count in LCD

if the Switch is OFF it wait for the condition when the Switch is ON

schematic diagram

full Program

###################################################################################

* File: switchcount.c
* Author: Ebin Ephrem

*/

#include<htc.h>

__CONFIG(0x193A);

#define RS RD0

#define RW RD1

#define EN RD2

#define DATA PORTB

#define S RC0

#define L RD3

void LCD_CMD(unsigned int value);

void LCD_DAT(unsigned int value);

void LCD_INIT();

void delay();

void main(void)

{

TRISC =0x0F;

TRISD =0x00;

TRISB = 0x00;

LCD_INIT();

int count;

count=0;

L=0;

while(1)

{

if( S == 1)

{

while(S==1);

L= ~L;

count = count+1;

LCD_CMD(0x01);

delay ();

LCD_DAT('0' + (count % 10));

}

void LCD_INIT()

{

LCD_CMD(0x01);

delay ();

LCD_CMD(0x38);

delay ();

LCD_CMD(0x0F);

delay ();

LCD_CMD(0x06);

delay ();

LCD_CMD(0x0c);

delay ();

LCD_CMD(0x80);

delay ();

}

void LCD_CMD(unsigned int value)

{

DATA = value;

RS=0;

RW=0;

EN=1;

delay ();

EN=0;

delay ();

}

void LCD_DAT(unsigned int value)

{

DATA= value ;

RS=1;

RW=0;

EN=1;

delay ();

EN=0;

delay();

}

void delay(void)

{

int counter = 0;

for (counter = 0; counter<1000; counter++) {

;

}

Remove the mask of passwords in any browser

If we use autofill settings there is a chance to forgot the password , your browser will always block the password box from passersby seeing it by using asterisks. To remove the mask and reveal your password, you just need to do a few things.

Follow the steps:

1. Right-click the password box and select "Inspect Element."This brings up the developer console

2.. On the line that starts with "input type=password"

3. Right click and select Edit HTML

4. change the word "password" to "text" ( type="password" to type="text")

http://w2s.us/xghrg3

Interfacing Keypad with PIC16F877A in C program using MPLAB X

This tutorial will show you how to read a 4x4 keypad input and write to an alphanumeric LCD interfaced to your PIC micro, it's pretty simple and straight forward.

First create a new project and add a c main file like in the steps for Blinking a LED using MPLAB X , PIC16F877A
Components
1.PIC16F877A micro controller
2. 4x4 matrix keypad

initial setup
supply logic 0 (0V or GND) to all 4 keypad row wires or set the row pins as output
Supply logic 1 (high voltage) to all 4 keypad coloum wires or set coloums as input

Steps to read a key from the keypad
1. Find the Row first, by selecting each row
2. scan the colum which pressed key is
3 Find the key pressed ,the function findKey() is for this

4. If we have at least one key pressed, then return from keypadread() will be non zero.

PROGRAM

#######################################################################

* File: main.c
* Author: Ebin Ephrem

*/

#include<htc.h>

#if defined(WDTE_OFF)

__CONFIG(WDTE_OFF & LVP_OFF);

#elif defined (WDTDIS)

__CONFIG(WDTDIS & LVPDIS);

#endif

char findKey(unsigned int a, unsigned int b);
char readKeyboard();

void main()
{
TRISB = 0xF0;

unsigned int re;
while(1)
{
re=0;
re= readKeyboard();
}
}
char readKeyboard()

{
unsigned int i = 0;
for(i=0;i<4;i++)
{
if(i == 0)
PORTB = 1;
else if(i == 1)
PORTB = 2;
else if(i == 2)
PORTB = 4;
else if(i == 3)
PORTB = 8;

if(RB4)
return findKey(i,0);
if(RB5)
return findKey(i,1);
if(RB6)
return findKey(i,2);
if(RB7)
return findKey(i,3);
}
return ' ';
}
char findKey(unsigned int a, unsigned int b) //generating key character
{

if(b == 0)
{
if(a == 3)
return '3';
else if(a == 2)
return '2';
else if(a == 1)
return '1';
else if(a == 0)
return '0';
}
else if(b == 1)
{
if(a == 3)
return '8';
else if(a == 2)
return '7';
else if(a == 1)
return '6';
else if(a == 0)
return '5';
}
else if(b == 2)
{
if(a == 3)
return 'b';
else if(a == 2)
return '8';
else if(a == 1)
return 'A';
else if(a == 0)
return '-';
}
else if(b == 3)
{
if(a == 3)
return 'C';
else if(a == 2)
return 'U';
else if(a == 1)
return 'E';
else if(a == 0)
return 'F';
}
}

######################################################################

you can modify the number of colums and rows for 3x4 keypad , and for the other keypads

Change and Customize Your Google Search Page

Most of us uses www.google.com for searching over internet .. Here is a method to change image for your google home page And make the homepage customised
It's a simple enough feature that we've heard rumors of here and there: Just go to Google.com,Pick any image from Google's Public gallery, your Picasa web album photos, or upload any image from your desktop

For this do following steps ..

1. open your browser and go to picasaweb.google.com

2. Log in to picasa with your Google ID and Password

3.You can select any albums and select upload in the top

4.A new window opens with Drag your Photo here ..or with select photo from your computer
select the photo that you want to make the homepage image

5.Click OK ..

6.Now go to www.google.com
7.Select the link Change background Image in the bottom left corner

8.A new window will appear to select image for your google home page. Select Your Picasa Web Photos or Your Recent Picks from the side tab on the window

9.Select the Picture that you want to make the google home page image ..

The google page will load your image as home page .. and njoy...
you can also set the popular images in the picasa web albums...

Now we heard that a serious security vulnerability was recently discovered that could wipe everything off of some Samsung phones. Although Samsung issued a patch for the Galaxy S III, it turns out it's not just Samsung devices that are affected. Here's how to find out if your Android device is vulnerable.

Essentially, some phones support special dial codes called USSDs (e.g., dialing *#06# to display the phone's IMEI number). Through malicious links in a website, SMS, NFC beam or QR code, hackers can perform a factory reset on your phone, lock the SIM card, and more—without warning.

Steps to find the your Android device is vulnerable , and make it secure by using an patch

1 . Go to the link http://dylanreeve.com/phone.php on your phones browser
2.If your phone is vulnerable , you'll immediately see your phone's IMEI number pop up.

If you are vulnerable, you should look for the latest updates for your device.Usually you can go to Settings > About Phone > System Update to check for available updates

Some browsers (most notably Opera) appear to offer some security by not handling the iframe injection code immediately.

Two apps have also been developed to protect against the vulnerability: Auto-reset blocker andTelStop.

Finally, as always, avoid clicking on any unknown links.

ANALOG TO DIGITAL CONVERTION using PIC16F877A and MPLABX

Many electrical signals around us are Analog in nature. That means a quantity varies directly with some other quantity. The first quantity is mostly voltage while that second quantity can be anything like temperature, pressure, light, force or acceleration.

The PIC16F877A has a built-in Analogue to Digital converter. What ADC does is basically convert an analogue voltage ranging from -Vref to +Vref (usually 0V to 5V) and converts it to a binary value. The ADC on the PIC16F877A has 10-bit resolution and this provides 1024 steps (2^10=1024) which is more than enough for normal applications.

Programming ADC in HI-TECH C for MPLAB

ADC is connect to the PIC CPU by 3 control register and 2 data register. The control registers are used to setup and give commands to the ADC. They also provides the status of ADC. The two data registers holds the 10 bit of converted data. Since each resister in PIC18 is of 8 bits therefore 2 registers are required to hold the 10bit data.

We will develop two functions to support ADC in our projects. One will help initialize the module and other will help us select any of the 13 channels and start the conversion. After the conversion is done it will return us the results.

I am not giving here the description of the control and data registers as they are very clearly explained in PIC18F4520's datasheet on page 223 to 225. I request you to download the datasheet and read the description so that you will have an Idea of what every bit in the registers do. As I told before, ADC is connected to the CPU via three control register and two data registers. The three control registers are :-

ADCON0 - Used to select analog input channel,start the conversion, check if the conversion is done and to switch on/off the module.(We use this in ADCRead() function.)

ADCON1 - Used to Select Voltage reference, and to configure ports as Analog of digital. (We leave these to defaults)

ADCON2 - Used to select ADC data format, Set acquisition time, ADC clock setup (We setup these in ADCInit() function)

First we configure the ADC to our needs in the ADCInit() function.

//Function to Initialise the ADC Module
void ADCInit()
{
   //We use default value for +/- Vref

   //VCFG0=0,VCFG1=0
   //That means +Vref = Vdd (5v) and -Vref=GEN

   //Port Configuration
   //We also use default value here too
   //All ANx channels are Analog

   /*
      ADCON2

      *ADC Result Right Justified.
      *Acquisition Time = 2TAD
      *Conversion Clock = 32 Tosc
   */

   ADCON2=0b10001010;
}

ADCRead function ...

//Function to Read given ADC channel (0-13)
unsigned int ADCRead(unsigned char ch)
{
   if(ch>13) return 0;  //Invalid Channel

   ADCON0=0x00;

   ADCON0=(ch<<2);   //Select ADC Channel

   ADON=1;  //switch on the adc module

   GODONE=1;  //Start conversion

   while(GODONE); //wait for the conversion to finish

   ADON=0;  //switch off adc

   return ADRES;
}

THE PROGRAM IS AVAILABLE ON GITHUB : https://github.com/ebine/

Services | Embedded Support | Reviews | Virtual Technologys

SERVFORU

How to Set Up a Timer in PIC16F877A

Using Timers in PIC16F877A

AODV routing Protocol simulation using NS2

Displaying a Word or String in an 16x2 LCD with PIC16F877A and MPLAB X

Counting the number of times pressed of Switch , C program in MPLAB X

Remove the mask of passwords in any browser

Interfacing Keypad with PIC16F877A in C program using MPLAB X

Change and Customize Your Google Search Page

Check your Android Device is vulnerable ? How to Make it Secure

ANALOG TO DIGITAL CONVERTION using PIC16F877A and MPLABX

Programming ADC in HI-TECH C for MPLAB

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