Experiment No. 2 : Push Button and Seven Segment Display Interface

In this experiment, we will program the PIC16F628A as an UP/DOWN Decade Counter. The count value will be displayed on a Seven-Segment Display and will be incremented/decremented by two push buttons on the board.

Experimental Setup:
The board has built in interface for a multiplexed 4-digit seven segment display (HS-5461AS2 from www.futurlec.com).We will select only one digit by connecting a Digit Select pin to Vcc, as shown in figure below. A black jumper wire is used for this purpose. The seven segments will be driven through PORTB (already wired on the board). Connect Push Buttons (PB3 and PB4) to RA1 and RA0 female headers using jumper wires.

Software:

We will use in-built 'Button Library' to detect push button press.

Here is the complete C program written for mikroC for PIC 2009.

/*

 * Project name:

     UP/DOWN Decimal Counter with Push Button and 7-Segment Interface

 * Copyright:

     (c) Rajendra Bhatt, 2009.

 * Description:

     This code is an example of Seven Segment Display and Push Button interface.

     A decimal counter value will be displayed on the seven segment display.

     The value of the counter can be incremented or decremented through push

     buttons.

 * Test configuration:

     MCU:             PIC16F628A

     The two push buttons are connected to RA0(Increment) and RA1(Decrement)

     and the seven segment display connected to PORTB (Segment a to PB.0,

     Segment b to PB.1 and so on)

*/

//-------------- Function to Return mask for common cathode 7-seg. display

unsigned short mask(unsigned short num) {

  switch (num) {

    case 0 : return 0x3F;

    case 1 : return 0x06;

    case 2 : return 0x5B;

    case 3 : return 0x4F;

    case 4 : return 0x66;

    case 5 : return 0x6D;

    case 6 : return 0x7D;

    case 7 : return 0x07;

    case 8 : return 0x7F;

    case 9 : return 0x6F;

  } //case end

}

unsigned int   digit;      // To Hold Decimal Value

unsigned short number;     // To Hold Equivalent Seven Segment Value

void main() {

  CMCON  |= 7;         // Disable Comparators

  TRISB = 0x00;        // Set PORTB direction to be output

  PORTB = 0x00;        // Turn OFF LEDs on PORTB

  TRISA0_bit = 1;      // PA.0 Input for Increment

  TRISA1_bit = 1;      // PA.1 Input for Decrement

  digit   =    0;  // Initial Value of Counter

  number  = mask(digit)   ;

  PORTB   = number;

  do {

    if (Button(&PORTA, 0, 1, 0)) {  // Detect logical one to zero

      Delay_ms(300);

      digit ++;                 // Increase Counter

      number  = mask(digit)   ;

      PORTB   = number;

    }

    if (Button(&PORTA, 1, 1, 0)) {  // Detect logical one to zero

      Delay_ms(300) ;

      digit = digit-1;                 // Decrease Counter

      number  = mask(digit)   ;

      PORTB   = number;                // Update flag

    }

  } while(1);                             // endless loop

}

Experiment Output Video: