電子愛好者的樂趣，想啥做啥，????????；不受拘束的想象力加上強大的動手能力，我們幾乎能做絕大部分東西，下面我們來一起簡單的”小試牛刀“，做個計算器耍耍。

使用到的東西元器件：4*4矩陣鍵盤，1602液晶模塊，arduino uno開發(fā)板，220Ω電阻

1602液晶模塊連接注意的引腳：
VCC:     液晶模塊供電正極
LED+：背光燈正極連接電源正極VCC
LED-：背光燈負(fù)極通過220Ω限流電阻連接負(fù)極GND
VO：設(shè)置液晶偏置電壓連接至GND
RW：讀寫模式引腳，我們這里只要寫，所以R/W接GND
GND:液晶模塊供電負(fù)極

我們來看下實際運行效果：

矩陣鍵盤A,B,C,D分別代表 +，-，X，/;  ' * '代表清除，' # '號代表' = '

代 碼 部 分：

#include #include #include LiquidCrystal lcd(13, 12, 11, 10, 9, 8);long first = 0;long second = 0;double total = 0;char customKey;const byte ROWS = 4;const byte COLS = 4;char keys[ROWS][COLS] = {

  {'1','2','3','+'},

  {'4','5','6','-'},

  {'7','8','9','*'},

  {'C','0','=','/'}};byte rowPins[ROWS] = {7,6,5,4}; //connect to the row pinouts of the keypadbyte colPins[COLS] = {3,2,1,0}; //connect to the column pinouts of the keypad//initialize an instance of class NewKeypadKeypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS); void setup(){

  lcd.begin(16, 2);               // start lcd

  for(int i=0;i<=3;i++);

  lcd.setCursor(0,0);

  lcd.print('Hello');

  lcd.setCursor(0,1);

  lcd.print('calc');

  delay(4000);

  lcd.clear();

  lcd.setCursor(0, 0);}void loop(){

  customKey = customKeypad.getKey();

  switch(customKey) 

  {

  case '0' ... '9': // This keeps collecting the first value until a operator is pressed '+-*/'

    lcd.setCursor(0,0);

    first = first * 10 + (customKey - '0');

    lcd.print(first);

    break;

  case '+':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('+');

    second = SecondNumber(); // get the collected the second number

    total = first + second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0; // reset values back to zero for next use

    break;

  case '-':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('-');

    second = SecondNumber();

    total = first - second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0;

    break;

  case '*':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('*');

    second = SecondNumber();

    total = first * second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0;

    break;

  case '/':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('/');

    second = SecondNumber();

    lcd.setCursor(0,3);

    second == 0 ? lcd.print('Invalid') : total = (float)first / (float)second;

    lcd.print(total);

    first = 0, second = 0;

    break;

  case 'C':

    total = 0;

    lcd.clear();

    break;

  }}long SecondNumber(){

      while( 1 )

      {

        customKey = customKeypad.getKey();

        if(customKey >= '0' && customKey <= '9')

        {

          second = second * 10 + (customKey - '0');

          lcd.setCursor(0,2);

          lcd.print(second);

        }

        if(customKey == '=') break;  //return second;

      }

     return second; }

代碼解釋：

我們這里用了arduino自帶的液晶庫#include 和按鍵庫#include

這樣我們只要將重心挪到計算器核心的算法開發(fā)上就好了。

定義四線驅(qū)動1602的引腳：

LiquidCrystal lcd(13, 12, 11, 10, 9, 8);

按鍵行和列符號定義：

char keys[ROWS][COLS] = {

  {'1','2','3','+'},

  {'4','5','6','-'},

  {'7','8','9','*'},

  {'C','0','=','/'}};

按鍵行和列引腳定義：

byte rowPins[ROWS] = {7,6,5,4}; byte colPins[COLS] = {3,2,1,0}; 

按鍵符號與行列引腳關(guān)聯(lián)：

Keypad customKeypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS); 

第一個部分運算字符輸入處理：

  case '0' ... '9':

    lcd.setCursor(0,0);

    first = first * 10 + (customKey - '0');

    lcd.print(first);

    break;

加法處理部分：

  case '+':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('+');

    second = SecondNumber();

    total = first + second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0;

    break;

減法處理部分：

case '-':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('-');

    second = SecondNumber();

    total = first - second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0;

    break;

乘法處理部分：

  case '*':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('*');

    second = SecondNumber();

    total = first * second;

    lcd.setCursor(0,3);

    lcd.print(total);

    first = 0, second = 0;

    break;

除法處理部分：除法里面還做了除0非法操作

  case '/':

    first = (total != 0 ? total : first);

    lcd.setCursor(0,1);

    lcd.print('/');

    second = SecondNumber();

    lcd.setCursor(0,3);

    second == 0 ? lcd.print('Invalid') : total = (float)first / (float)second;

    lcd.print(total);

    first = 0, second = 0;

    break;

清除計算處理：

  case 'C':

    total = 0;

    lcd.clear();

    break;

另外還有第二個數(shù)據(jù)字符輸入處理：

long SecondNumber(){

      while( 1 )

      {

        customKey = customKeypad.getKey();

        if(customKey >= '0' && customKey <= '9')

        {

          second = second * 10 + (customKey - '0');

          lcd.setCursor(0,2);

          lcd.print(second);

        }

        if(customKey == '=') break;  //return second;

      }

     return second; }

我們輸入第一個數(shù)據(jù)字符串后，如果檢測到有輸入運算符，那么就直接進入到第二個數(shù)據(jù)字符串里面，一直到有輸入“=”符號，輸出計算結(jié)果，并跳出當(dāng)前計算；注意到每個數(shù)據(jù)字符串里面還做了數(shù)據(jù)轉(zhuǎn)換，將字符轉(zhuǎn)換為十進制數(shù)。

大家可以思考下？

我們看到里面的數(shù)據(jù)定義都是long型的，如果超過long型所能表達的最大數(shù)據(jù)會出現(xiàn)什么情況？又該如何處理？大家可以嘗試去完善下。

另外我們這里面基本上都是調(diào)用arduino的庫函數(shù)在處理，如果放到51單片機上或者其它單片機上，那么又該如何操作？這些函數(shù)大家都可以大膽的去嘗試實現(xiàn)。