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Saturday, May 28, 2022

A DIY Calculator Using PIC16F876A

I decide to make a simple digital calculator with my own components, seven-segment display. PIC16F876A, and push button, etc. However it's not useful in current application because a calculator presents in many electronics device such as a smart phone, tablet, and personal computer, etc.

A DIY Calculator Using PIC16F876A
A DIY Calculator Using PIC16F876A 

This calculator is able to handle up to 8 digits, including a negative sign. It can perform arithmetic addition, subtraction, multiplication, and division. The data type is only signed integer number. 

I use MikroC Pro for PIC to program this typical 8-bit controller. The total lines of code is quite high.

  1.  
  2.  
  3. #define GA (1<<3)
  4. char keypadPort at PORTB;
  5. char key_char[16]= {7,8,9,15,4,5,6,14,1,2,3,13,10,0,11,12};
  6. char send_key,dig[8];
  7. unsigned char cnt;
  8.  
  9. void interrupt(void){
  10.     if(INTCON.TMR0IF)
  11.     cnt++;
  12.     INTCON.TMR0IF=0;
  13.     }
  14.  
  15. void system_init();
  16. void ssd_out();
  17.  
  18. void main() {
  19.      char key=0,old_key=0;
  20.      char i=0,j=0;
  21.      char CntKey=0;
  22.      system_init();
  23.      while(1){
  24.        key=Keypad_Key_Click();
  25.        if(key!=0&&CntKey<8){
  26.                   send_key=key-1;
  27.                   /*dig[5]=dig[4];
  28.                   dig[4]=dig[3];
  29.                   dig[3]=dig[2];
  30.                   dig[2]=dig[1];
  31.                   dig[1]=dig[0];*/
  32.                   for(i=7;i>0;i--) dig[i]=dig[i-1];
  33.                   dig[0]=key_char[send_key];
  34.                   CntKey++;
  35.                   }
  36.  
  37.        ssd_out();
  38.       }
  39. }
  40.  
  41. void system_init(){
  42.      TRISC=0x00;
  43.      TRISA=0x00;
  44.      PORTA=0x00;
  45.      PORTC=0x00;
  46.      ADCON1=0x07;
  47.      OPTION_REG=0x85;
  48.      INTCON.GIE=1;
  49.      INTCON.TMR0IE=1;
  50.      INTCON.TMR0IF=0;
  51.      Keypad_Init();
  52.      cnt=0;
  53.      send_key=0;
  54. }
  55.  
  56. void ssd_out(){
  57. const char sg[16]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,
  58. 0x07,0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x79,0x71} ;
  59. // const char dg[6]={0x20,0x10,0x08,0x04,0x02,0x01};
  60.      switch(cnt){
  61.                  case 1:
  62.                       PORTA=0x00;
  63.                       PORTC=sg[dig[7]];
  64.                       PORTA=0x00|GA;
  65.                       break;
  66.  
  67.                  case 2:
  68.                       PORTA=0x00;
  69.                       PORTC=sg[dig[6]];
  70.                       PORTA=0x01|GA;
  71.                       break;
  72.  
  73.                  case 3:
  74.                       PORTA=0x00;
  75.                       PORTC=sg[dig[5]];
  76.                       PORTA=0x02|GA;
  77.                       break;
  78.  
  79.                  case 4:
  80.                       PORTA=0x00;
  81.                       PORTC=sg[dig[4]];
  82.                       PORTA=0x03|GA;
  83.                       break;
  84.  
  85.                  case 5:
  86.                       PORTA=0x00;
  87.                       PORTC=sg[dig[3]];
  88.                       PORTA=0x04|GA;
  89.                       break;
  90.  
  91.                  case 6:
  92.                       PORTA=0x00;
  93.                       PORTC=sg[dig[2]];
  94.                       PORTA=0x05|GA;
  95.                       break;
  96.  
  97.                  case 7:
  98.                       PORTA=0x00;
  99.                       PORTC=sg[dig[1]];
  100.                       PORTA=0x06|GA;
  101.                       break;
  102.  
  103.                  case 8:
  104.                       PORTA=0x00;
  105.                       PORTC=sg[dig[0]];
  106.                       PORTA=0x07|GA;
  107.                       break;
  108.  
  109.                  case 9:
  110.                       cnt=1;
  111.                       PORTA=0x00;
  112.                       break;
  113.                  }
  114.  
  115. }

I use keypad library of this compiler to scan its 4x4 matrix keypad.

A DIY Calculator Using PIC16F876A
Schematic Diagram

The PCB is assumed to be a single side layer. It's easy to fabricate at home.

A DIY Calculator Using PIC16F876A
Bottom Layer copper normal no mirror

A DIY Calculator Using PIC16F876A
Top silk normal no mirror
A DIY Calculator Using PIC16F876A
A sample 3D design

A DIY Calculator Using PIC16F876A
Top side

A DIY Calculator Using PIC16F876A
Bottom side

Click here to download its source file.



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