PIC Countdown Timer (0-99)

This project describes how to program PIC16F628A to function as a 00-99 min programmable timer. User can set any time between 00-99 minutes and can turn ON a device for that period. The device will be automatically turned OFF after the time expires. For demonstration, the ON/OFF condition of device is simulated by switching LED ON and OFF. With the use of three input switches (unit, ten, start/stop) the user can set ON time of the timer and can also control Start/Stop operation. The two time set switches are for selecting unit and tens digit of minute time interval (00-99). Once you set the value of minute interval, pressing the Start/Stop will turn the timer ON (LED will glow), and pressing the same button again at any point of time during timer operation will interrupt the process (LED will turn OFF) and the timer will be reset. LCD display will provide timer status and user interface for setting time.






Circuit

Code
Compiled using MikroC for PIC




/*
  ############################################

  MCU:16F628A
  Project: PIC Countdown Timer (0-99)
  Vishal K M
  Jan 10, 2012
  ############################################

 
*/

// LCD module connections
sbit LCD_RS at RA0_bit;
sbit LCD_EN at RA1_bit;
sbit LCD_D4 at RB4_bit;
sbit LCD_D5 at RB5_bit;
sbit LCD_D6 at RB6_bit;
sbit LCD_D7 at RB7_bit;
sbit LCD_RS_Direction at TRISA0_bit;
sbit LCD_EN_Direction at TRISA1_bit;
sbit LCD_D4_Direction at TRISB4_bit;
sbit LCD_D5_Direction at TRISB5_bit;
sbit LCD_D6_Direction at TRISB6_bit;
sbit LCD_D7_Direction at TRISB7_bit;
// End LCD module connections

// Tact switches and Relay ports
sbit Relay at RA3_bit;
sbit SS_Select at RB0_bit;    // Start Stop Timer Select
sbit Unit_Button at RB1_bit;  // Set unit min
sbit Ten_Button at RB2_bit;   // Set ten min


// Messages
char Message1[]="Timer by VISHAL";
char Message2[]="Device ON";
char Message3[]="Device OFF";
char Message4[]="Set Time:    min";
char Message5[]="Time Left:   min";
unsigned short i, j, unit=0, ten=0, ON_OFF=0, index=0, clear, time;
char *digit = "00";
// 300ms Delay
void Delay_300(){
 Delay_ms(300);
}

void Display_Digits(){
 digit[1]=unit+48;
 digit[0]=ten+48;
 Lcd_Out(2,11,digit);
}

void start_timer(unsigned short MinVal){
 unsigned short temp1, temp2;
 Relay = 1;
 ON_OFF = 1;
 Lcd_Cmd(_LCD_CLEAR);
 Lcd_Out(1,1,Message2);
 Lcd_Out(2,1,Message5);
 OPTION_REG = 0x80 ;
 INTCON = 0x90;
 for (i=0; i<MinVal; i++){
  temp1 = (MinVal-i)%10 ;
  temp2 = (MinVal-i)/10 ;
  Lcd_Chr(2, 12, temp2+48);
  Lcd_Chr(2, 13, temp1+48);
  j=1;
  do {
  Delay_ms(1000);
  j++;
  } while(((j<=60) && (Clear ==0)));
  if (Clear) {
   Relay = 0;
   Delay_ms(500);
   Lcd_Out(1,1,Message3);
   INTCON = 0x00;
   goto stop;
   }
 }
 stop:
 Relay = 0;
 ON_OFF = 0;
 unit = 0;
 ten = 0;
 clear = 1;
}

void interrupt(void){
  if (INTCON.INTF == 1)   // Check if INTF flag is set
   {
    Clear = 1;
    INTCON.INTF = 0;       // Clear interrupt flag before exiting ISR
   }
  }

void main() {
  CMCON  |= 7;                       // Disable Comparators
  TRISB = 0b00001111;
  TRISA = 0b11110000;
  Relay = 0;

  Lcd_Init();                        // Initialize LCD
 start:
  clear = 0;
  Lcd_Cmd(_LCD_CLEAR);               // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off
  Lcd_Out(1,1,Message1);
  Lcd_Out(2,1,Message4);
  Display_Digits()  ;
 do {

     if(!Unit_Button){
     Delay_300();
     unit ++;
     if(unit==10) unit=0;
     Display_Digits();
    } // If !Unit_Button

    if(!Ten_Button){
     Delay_300();
     ten ++;
     if(ten==10) ten=0;
     Display_Digits();
    } // If !Ten_Button

    if(!SS_Select){
     Delay_300();
     time = ten*10+unit ;
     if(time > 0) start_timer(time);
    } // If !SS_Select

    if(clear){
     goto start;
    }
   } while(1);
}







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PIC 4 Bit LCD Interfacing Tutorial

The mikroC PRO for PIC provides a library for communication with Lcds (with HD44780 compliant controllers) through the 4-bit interface. An example of Lcd connections is given on the schematic at the bottom of this page.

For LCD Basics: Character LCD Basics  

External dependencies of Lcd Library

The following variables must be defined in all projects using Lcd Library :	Description :	Example :
extern sfr sbit LCD_RS:	Register Select line.	sbit LCD_RS at RB4_bit;
extern sfr sbit LCD_EN:	Enable line.	sbit LCD_EN at RB5_bit;
extern sfr sbit LCD_D7;	Data 7 line.	sbit LCD_D7 at RB3_bit;
extern sfr sbit LCD_D6;	Data 6 line.	sbit LCD_D6 at RB2_bit;
extern sfr sbit LCD_D5;	Data 5 line.	sbit LCD_D5 at RB1_bit;
extern sfr sbit LCD_D4;	Data 4 line.	sbit LCD_D4 at RB0_bit;
extern sfr sbit LCD_RS_Direction;	Register Select direction pin.	sbit LCD_RS_Direction at TRISB4_bit;
extern sfr sbit LCD_EN_Direction;	Enable direction pin.	sbit LCD_EN_Direction at TRISB5_bit;
extern sfr sbit LCD_D7_Direction;	Data 7 direction pin.	sbit LCD_D7_Direction at TRISB3_bit;
extern sfr sbit LCD_D6_Direction;	Data 6 direction pin.	sbit LCD_D6_Direction at TRISB2_bit;
extern sfr sbit LCD_D5_Direction;	Data 5 direction pin.	sbit LCD_D5_Direction at TRISB1_bit;
extern sfr sbit LCD_D4_Direction;	Data 4 direction pin.	sbit LCD_D4_Direction at TRISB0_bit;

Library Routines

• Lcd_Init


• Lcd_Out


• Lcd_Out_Cp


• Lcd_Chr


• Lcd_Chr_Cp


• Lcd_Cmd

Lcd_Init

Prototype	void Lcd_Init();
Returns	Nothing.
Description	Initializes Lcd module.
Requires	Global variables: LCD_D7: Data bit 7 LCD_D6: Data bit 6 LCD_D5: Data bit 5 LCD_D4: Data bit 4 LCD_RS: Register Select (data/instruction) signal pin LCD_EN: Enable signal pin LCD_D7_Direction: Direction of the Data 7 pin LCD_D6_Direction: Direction of the Data 6 pin LCD_D5_Direction: Direction of the Data 5 pin LCD_D4_Direction: Direction of the Data 4 pin LCD_RS_Direction: Direction of the Register Select pin LCD_EN_Direction: Direction of the Enable signal pin must be defined before using this function.
Example	// Lcd pinout settings sbit LCD_RS at RB4_bit; sbit LCD_EN at RB5_bit; sbit LCD_D7 at RB3_bit; sbit LCD_D6 at RB2_bit; sbit LCD_D5 at RB1_bit; sbit LCD_D4 at RB0_bit; // Pin direction sbit LCD_RS_Direction at TRISB4_bit; sbit LCD_EN_Direction at TRISB5_bit; sbit LCD_D7_Direction at TRISB3_bit; sbit LCD_D6_Direction at TRISB2_bit; sbit LCD_D5_Direction at TRISB1_bit; sbit LCD_D4_Direction at TRISB0_bit; ... Lcd_Init();

Lcd_Out

Prototype	void Lcd_Out(char row, char column, char *text);
Returns	Nothing.
Description	Prints text on Lcd starting from specified position. Both string variables and literals can be passed as a text. Parameters : row: starting position row number column: starting position column number text: text to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write text "Hello!" on Lcd starting from row 1, column 3: Lcd_Out(1, 3, "Hello!");

Lcd_Out_Cp

Prototype	void Lcd_Out_Cp(char *text);
Returns	Nothing.
Description	Prints text on Lcd at current cursor position. Both string variables and literals can be passed as a text. Parameters : text: text to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write text "Here!" at current cursor position: Lcd_Out_Cp("Here!");

Lcd_Chr

Prototype	void Lcd_Chr(char row, char column, char out_char);
Returns	Nothing.
Description	Prints character on Lcd at specified position. Both variables and literals can be passed as a character. Parameters : row: writing position row number column: writing position column number out_char: character to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write character "i" at row 2, column 3: Lcd_Chr(2, 3, 'i');

Lcd_Chr_Cp

Prototype	void Lcd_Chr_Cp(char out_char);
Returns	Nothing.
Description	Prints character on Lcd at current cursor position. Both variables and literals can be passed as a character. Parameters : out_char: character to be written
Requires	The Lcd module needs to be initialized. See Lcd_Init routine.
Example	// Write character "e" at current cursor position: Lcd_Chr_Cp('e');

Lcd_Cmd

Prototype	void Lcd_Cmd(char out_char);
Returns	Nothing.
Description	Sends command to Lcd. Parameters : out_char: command to be sent   Note : Predefined constants can be passed to the function, see Available Lcd Commands.
Requires	The Lcd module needs to be initialized. See Lcd_Init table.
Example	// Clear Lcd display: Lcd_Cmd(_LCD_CLEAR);

Available Lcd Commands

Lcd Command	Purpose
_LCD_FIRST_ROW	Move cursor to the 1st row
_LCD_SECOND_ROW	Move cursor to the 2nd row
_LCD_THIRD_ROW	Move cursor to the 3rd row
_LCD_FOURTH_ROW	Move cursor to the 4th row
_LCD_CLEAR	Clear display
_LCD_RETURN_HOME	Return cursor to home position, returns a shifted display to its original position. Display data RAM is unaffected.
_LCD_CURSOR_OFF	Turn off cursor
_LCD_UNDERLINE_ON	Underline cursor on
_LCD_BLINK_CURSOR_ON	Blink cursor on
_LCD_MOVE_CURSOR_LEFT	Move cursor left without changing display data RAM
_LCD_MOVE_CURSOR_RIGHT	Move cursor right without changing display data RAM
_LCD_TURN_ON	Turn Lcd display on
_LCD_TURN_OFF	Turn Lcd display off
_LCD_SHIFT_LEFT	Shift display left without changing display data RAM
_LCD_SHIFT_RIGHT	Shift display right without changing display data RAM

Code

// LCD module connections

sbit LCD_RS at RB4_bit;

sbit LCD_EN at RB5_bit;

sbit LCD_D4 at RB0_bit;

sbit LCD_D5 at RB1_bit;

sbit LCD_D6 at RB2_bit;

sbit LCD_D7 at RB3_bit;

sbit LCD_RS_Direction at TRISB4_bit;

sbit LCD_EN_Direction at TRISB5_bit;

sbit LCD_D4_Direction at TRISB0_bit;

sbit LCD_D5_Direction at TRISB1_bit;

sbit LCD_D6_Direction at TRISB2_bit;

sbit LCD_D7_Direction at TRISB3_bit;

// End LCD module connections

char txt1[] = "Embedded";   

char txt2[] = "Projects";

char txt3[] = "Lcd 4 bit";

char txt4[] = "Example";

char i;                              // Loop variable

void Move_Delay() {                  // Function used for text moving

  Delay_ms(500);                     // You can change the moving speed here

}

void main(){

 

  Lcd_Init();                        // Initialize LCD

  Lcd_Cmd(_LCD_CLEAR);               // Clear display

  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off

  Lcd_Out(1,6,txt3);                 // Write text in first row

  Lcd_Out(2,6,txt4);                 // Write text in second row

  Delay_ms(2000);

  Lcd_Cmd(_LCD_CLEAR);               // Clear display

  Lcd_Out(1,1,txt1);                 // Write text in first row

  Lcd_Out(2,5,txt2);                 // Write text in second row

  Delay_ms(2000);

  // Moving text

  for(i=0; i<4; i++) {               // Move text to the right 4 times

    Lcd_Cmd(_LCD_SHIFT_RIGHT);

    Move_Delay();

  }

  while(1) {                         // Endless loop

    for(i=0; i<8; i++) {             // Move text to the left 7 times

      Lcd_Cmd(_LCD_SHIFT_LEFT);

      Move_Delay();

    }

    for(i=0; i<8; i++) {             // Move text to the right 7 times

      Lcd_Cmd(_LCD_SHIFT_RIGHT);

      Move_Delay();

    }

  }

}