The document describes a mini 4x4 keypad calculator that connects an HC11-CPU microcontroller to a LCD display. It includes code for scanning the keypad, performing basic math operations, and displaying results on the LCD. Key functions include entering numbers, selecting operators, clearing values, and calculating results when the equals key is pressed.

2. MINI – KEY 4x4
port 14 pin to 10 pin

3. HC11-CPU ET-EXP4

4. key switch connect MCS 51 and LCD
Shift = key switch
= “ ” Shift
= “ ” Shift
sin
= “ ” Shift
cos

5. = “ ” Shift
tan
= “ ” Shift
log
= “ ” Shift
sqrt
= “ ” Shift
epxp
= “ ” Shift
pow 2
8= “ ” Shift
pow 3
9= “ ” Shift
absolute
+= “ ”
- = “ ”
*= “ ”
/ = “ ”

6. key switch
#include <at89c51xd2.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
sbit E = P0^2;
sbit RS = P0^0;
sbit a1 = P1^0; //row
sbit a2 = P1^1;
sbit a3 = P1^2;
sbit a4 = P1^3;
sbit b1 = P1^4; //col
sbit b2 = P1^5;
sbit b3 = P1^6;
sbit b4 = P1^7;
char keyp()
{
char nkey = ' ';

7. a1 = 0; a2 = 1; a3 = 1; a4 = 1;
if(a1 == 0 && b1 == 0) nkey = '7';
else if(a1 == 0 && b2 == 0) nkey = '4';
else if(a1 == 0 && b3 == 0) nkey = '1';
else if(a1 == 0 && b4 == 0) nkey = 'c';
a1 = 1; a2 = 0; a3 = 1; a4 = 1;
if(a2 == 0 && b1 == 0) nkey = '8';
else if(a2 == 0 && b2 == 0) nkey = '5';
else if(a2 == 0 && b3 == 0) nkey = '2';
else if(a2 == 0 && b4 == 0) nkey = '0';
a1 = 1; a2 = 1; a3 = 0; a4 = 1;
if(a3 == 0 && b1 == 0) nkey = '9';
else if(a3 == 0 && b2 == 0) nkey = '6';
else if(a3 == 0 && b3 == 0) nkey = '3';
else if(a3 == 0 && b4 == 0) nkey = '=';
a1 = 1; a2 = 1; a3 = 1; a4 = 0;
if(a4 == 0 && b1 == 0) nkey = '/';
else if(a4 == 0 && b2 == 0) nkey = '*';
else if(a4 == 0 && b3 == 0) nkey = '-';
else if(a4 == 0 && b4 == 0) nkey = '+';
return nkey;
}
void delay(unsigned int count)
{
unsigned int i;
for(i=0;i<=count;i++);

8. }
void write_data(unsigned char c)
{
P0 = (c & 0xF0) | 0x01;
E = 1; delay(200);
E = 0; delay(200);
P0 = ((c << 4) & 0xF0) | 0x01;
E = 1; delay(200);
E = 0; delay(200);
}
void write_init(unsigned char i)
{
P0 = (i & 0xF0);
E = 1; delay(200);
E = 0; delay(200);
P0 = ((i<<4) & 0xF0) ;
E = 1; delay(200);
E = 0; delay(200);
}
void write_string(unsigned char *s)
{
unsigned short i, len;
len = strlen(s);
for(i = 0;i <= (len-1);i++)
{
write_data(s[i]);
}

9. }
float cal (float f, float l, unsigned char o)
{
float ans = 0;
if(o == '+') ans = f + l;
else if(o == '-') ans = f - l;
else if(o == '*') ans = f * l;
else if(o == '/') ans = f / l;
else if(o == 's') ans = sin(f);
else if(o == 'c') ans = cos(f);
else if(o == 't') ans = tan(f);
else if(o == 'l') ans = log(f);
else if(o == 'q') ans = sqrt(f);
else if(o == 'e') ans = exp(f);
else if(o == 'p') ans = pow(2,l);
else if(o == 'P') ans = pow(3,l);
else if(o == 'S') ans = abs(f);
return ans;
}
void main ()
{
unsigned char keypad;
unsigned char Fnum[7], Lnum[7], Ans[15];
float fnum = 0, lnum = 0, ans = 0;
unsigned char Oper = ' ';
unsigned short countdigit = 0;
unsigned short c, chkc = 1;
write_init(0x33);

10. write_init(0x32);
write_init(0x28);
write_init(0x0e);
write_init(0x01);
write_init(0x0c);
while(1)
{
keypad = keyp();
if(countdigit <= 5 && keypad >= '0' && keypad <= '9')
{
if(Oper == ' ') Fnum[countdigit] = keypad;
else Lnum[countdigit] = keypad;
write_data(keypad);
countdigit++;
}
else if(keypad == '+')
{
Oper = '+';
write_data('+');
countdigit = 0;
}
else if(keypad == '-')
{
Oper = '-';
write_data('-');
countdigit = 0;
}
else if(keypad == '*')
{

11. Oper = '*';
write_data('*');
countdigit = 0;
}
else if(keypad == '/')
{
Oper = '/';
write_data('/');
countdigit = 0;
}
else if(keypad == 'c')
{
chkc = 1;
while(chkc)
{
keypad = keyp();
if(keypad == '0')
{
write_init(0x01);
write_init(0x80);
countdigit = 0;
Oper = ' ';
for(c = 0;c <= 14;c++)
{
if(c<=7)
{
Fnum[c] = ' ';
Lnum[c] = ' ';
}

12. Ans[c] = ' ';
}
chkc = 0;
}
else if(keypad == '1')
{
Oper = 's';
write_string("sin ");
chkc = 0;
}
else if(keypad == '2')
{
Oper = 'c';
write_string("cos ");
chkc = 0;
}
else if(keypad == '3')
{
Oper = 't';
write_string("tan ");
chkc = 0;
}
else if(keypad == '4')
{
Oper = 'l';
write_string("log ");
chkc = 0;
}
else if(keypad == '5')

13. {
Oper = 'q';
write_string("sqrt ");
chkc = 0;
}
else if(keypad == '6')
{
Oper = 'e';
write_string("epxp ");
chkc = 0;
}
else if(keypad == '7')
{
Oper = 'p';
write_string("power 2 ");
chkc = 0;
}
else if(keypad == '8')
{
Oper = 'P';
write_string("power 3 ");
chkc = 0;
}
else if(keypad == '9')
{
Oper = 'S';
write_string("absolute ");
chkc = 0;
while(keypad !=' ')

14. {
keypad = keyp();
}
}
}
else if(keypad == '=' && Oper != ' ')
{
fnum = atof(Fnum);
lnum = atof(Lnum);
ans = cal(fnum,lnum,Oper);
sprintf(Ans,"%0.3f",ans);
write_init(0xC0);
write_data('=');
write_string(Ans);
}
while(keypad !=' ')
{
keypad = keyp();
}
}
}