89c51单片机简易计算器

实现一个简易的计算器，可以使用 89c51 单片机和一些基本的电子元件。

首先，需要连接一个 16x2 LCD 显示器，用于显示计算器的输入和输出。然后，需要连接一些按钮，用于输入数字和操作符。这些按钮可以使用矩阵键盘或单独的按钮连接到单片机的 GPIO 引脚上。

接下来，需要编写程序来读取按钮输入和显示结果。程序应该能够处理加、减、乘、除四种基本的数学运算，并能够处理小数点和清除输入。

以下是一个简单的代码示例：

#include <reg51.h>

#define LCD_RS P1_0
#define LCD_RW P1_1
#define LCD_E  P1_2
#define LCD_D4 P1_3
#define LCD_D5 P1_4
#define LCD_D6 P1_5
#define LCD_D7 P1_6

void delay(unsigned int ms) {
    unsigned int i, j;
    for (i = 0; i < ms; i++) {
        for (j = 0; j < 120; j++) {
            // do nothing
        }
    }
}

void lcd_cmd(unsigned char cmd) {
    LCD_RS = 0;
    LCD_RW = 0;
    LCD_E = 1;
    LCD_D4 = cmd >> 4;
    LCD_D5 = cmd >> 5;
    LCD_D6 = cmd >> 6;
    LCD_D7 = cmd >> 7;
    delay(1);
    LCD_E = 0;
    delay(1);
    LCD_D4 = cmd & 0x0F;
    LCD_D5 = (cmd & 0x1F) << 1;
    LCD_D6 = (cmd & 0x3F) << 2;
    LCD_D7 = (cmd & 0x7F) << 3;
    delay(1);
    LCD_E = 1;
    delay(1);
    LCD_E = 0;
    delay(1);
}

void lcd_data(unsigned char data) {
    LCD_RS = 1;
    LCD_RW = 0;
    LCD_E = 1;
    LCD_D4 = data >> 4;
    LCD_D5 = data >> 5;
    LCD_D6 = data >> 6;
    LCD_D7 = data >> 7;
    delay(1);
    LCD_E = 0;
    delay(1);
    LCD_D4 = data & 0x0F;
    LCD_D5 = (data & 0x1F) << 1;
    LCD_D6 = (data & 0x3F) << 2;
    LCD_D7 = (data & 0x7F) << 3;
    delay(1);
    LCD_E = 1;
    delay(1);
    LCD_E = 0;
    delay(1);
}

void lcd_init() {
    lcd_cmd(0x33);
    lcd_cmd(0x32);
    lcd_cmd(0x28);
    lcd_cmd(0x0C);
    lcd_cmd(0x06);
    lcd_cmd(0x01);
    delay(10);
}

unsigned char read_key() {
    unsigned char key = 0xFF;
    unsigned char row, col;
    for (row = 0; row < 4; row++) {
        P2 = ~(1 << row);
        col = P2 & 0x0F;
        if (col != 0x0F) {
            key = row * 4 + col;
            break;
        }
    }
    return key;
}

unsigned char get_digit() {
    unsigned char digit = 0;
    while (1) {
        unsigned char key = read_key();
        if (key != 0xFF) {
            if (key == 0x0D) { // enter
                break;
            } else if (key == 0x0C) { // clear
                digit = 0;
                break;
            } else if (key >= 0x00 && key <= 0x09) { // 0-9
                digit = digit * 10 + (key & 0x0F);
                lcd_data(key + '0');
            } else if (key == 0x0A) { // .
                lcd_data('.');
            }
            while (read_key() != 0xFF) {
                // wait for key release
            }
        }
    }
    return digit;
}

unsigned char get_operator() {
    unsigned char op = 0;
    while (1) {
        unsigned char key = read_key();
        if (key != 0xFF) {
            if (key == 0x0D) { // enter
                break;
            } else if (key == 0x0C) { // clear
                op = 0;
                break;
            } else if (key == 0x0B) { // +
                op = '+';
                lcd_data('+');
            } else if (key == 0x07) { // -
                op = '-';
                lcd_data('-');
            } else if (key == 0x03) { // *
                op = '*';
                lcd_data('*');
            } else if (key == 0x06) { // /
                op = '/';
                lcd_data('/');
            }
            while (read_key() != 0xFF) {
                // wait for key release
            }
        }
    }
    return op;
}

void main() {
    lcd_init();
    lcd_cmd(0x80);
    while (1) {
        unsigned char a = get_digit();
        unsigned char op = get_operator();
        unsigned char b = get_digit();
        lcd_cmd(0xC0);
        if (op == '+') {
            lcd_data(a + b);
        } else if (op == '-') {
            lcd_data(a - b);
        } else if (op == '*') {
            lcd_data(a * b);
        } else if (op == '/') {
            lcd_data(a / b);
        } else {
            lcd_data('E');
        }
        while (read_key() != 0xFF) {
            // wait for key release
        }
    }
}

这段代码实现了一个简单的计算器，可以通过矩阵键盘输入数字和操作符，并在 LCD 显示器上显示结果。需要注意的是，这个计算器并没有处理优先级和括号等复杂的数学运算，只能处理两个数字之间的基本四则运算。