利用矩阵按键和LCD1602实现计算器功能（加减除、十进制和二进制转换） 注：除法运算结果显示保留两位小数

下面是一个简单的示例代码，实现了加减乘除和十进制、二进制之间的转换，并且在除法运算时保留两位小数。这份代码主要使用了 Arduino 的 LiquidCrystal 库。

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int operand1 = 0;
int operand2 = 0;
char operatorSymbol = '+';
bool isBinaryMode = false;

void setup() {
  lcd.begin(16, 2);
  lcd.print("Calculator");
  delay(1000);
  lcd.clear();
}

void loop() {
  int key = getKeyPressed();
  if (key != -1) {
    if (key >= 0 && key <= 9) {
      if (operatorSymbol == '=') {
        clearResult();
      }
      if (isBinaryMode) {
        operand1 = operand1 * 2 + key;
      } else {
        operand1 = operand1 * 10 + key;
      }
      lcd.print(key);
    } else if (key == 10) {   // A: +
      applyOperator('+');
    } else if (key == 11) {   // B: -
      applyOperator('-');
    } else if (key == 12) {   // C: *
      applyOperator('*');
    } else if (key == 13) {   // D: /
      applyOperator('/');
    } else if (key == 14) {   // *
      isBinaryMode = !isBinaryMode;
      if (isBinaryMode) {
        operand1 = convertToBinary(operand1);
      } else {
        operand1 = convertToDecimal(operand1);
      }
      clearResult();
      lcd.setCursor(0, 1);
      lcd.print(isBinaryMode ? "B" : "D");
    } else if (key == 15) {   // #
      clearResult();
      operand1 = 0;
      operand2 = 0;
      operatorSymbol = '+';
      isBinaryMode = false;
    }
  }
}

int getKeyPressed() {
  int key = -1;
  int row = -1;
  for (int i = 0; i < 4; i++) {
    digitalWrite(i + 6, LOW);
    for (int j = 0; j < 4; j++) {
      if (digitalRead(j + 2) == LOW) {
        row = i;
        key = j + i * 4;
      }
    }
    digitalWrite(i + 6, HIGH);
  }
  if (row != -1) {
    return key;
  } else {
    return -1;
  }
}

void applyOperator(char op) {
  if (operatorSymbol == '=') {
    operand1 = operand2;
  }
  operatorSymbol = op;
  clearResult();
  lcd.print(op);
}

void clearResult() {
  lcd.setCursor(0, 1);
  lcd.print("               ");
  lcd.setCursor(0, 1);
}

void displayResult(int result) {
  if (isBinaryMode) {
    lcd.print(String(result, BIN));
  } else {
    lcd.print(result);
  }
}

int convertToBinary(int decimal) {
  int binary = 0;
  int base = 1;
  while (decimal > 0) {
    binary += (decimal % 2) * base;
    decimal /= 2;
    base *= 10;
  }
  return binary;
}

int convertToDecimal(int binary) {
  int decimal = 0;
  int base = 1;
  while (binary > 0) {
    decimal += (binary % 10) * base;
    binary /= 10;
    base *= 2;
  }
  return decimal;
}

void calculate() {
  if (operatorSymbol == '+') {
    operand2 = operand1;
  } else if (operatorSymbol == '-') {
    operand2 -= operand1;
  } else if (operatorSymbol == '*') {
    operand2 *= operand1;
  } else if (operatorSymbol == '/') {
    float result = (float) operand2 / (float) operand1;
    clearResult();
    lcd.print(result, 2);
    delay(3000);
    clearResult();
    operand2 = (int) result;
  }
  displayResult(operand2);
  operatorSymbol = '=';
}

其中，`getKeyPressed()` 函数用于读取矩阵按键的输入，返回值为按下的键的编号（0-15），如果没有按键按下则返回 -1。`applyOperator()` 函数用于应用运算符，根据当前的运算符和操作数进行相应的运算。`convertToBinary()` 和 `convertToDecimal()` 函数用于实现十进制和二进制之间的转换。`calculate()` 函数用于计算结果，并将结果显示在 LCD1602 显示器上。