Arduino Uno的Rx和Tx引脚不能用作通过USB进行串行通信的输入吗？

我目前正在从事一个涉及LCD，传感器和键盘的项目。

Arduino Uno有14个输入/输出引脚（0-13，0为Rx，1为Tx）。

LCD本身占用5个引脚（引脚8-12），传感器1（引脚7）和键盘7（引脚0-6），这很好，因为我有14个电位引脚。

因此，我下载了一个基本程序来快速测试键盘并调整必要的变量。我想通过串行通信在计算机上显示数字。第1行和第4行有效，第2行和第3行无效。小键盘不会出错，因为我测量了每种组合的电阻。然后我意识到保存有关第2行和第3行信息的引脚已连接到Arduino Uno的引脚0和1（Rx＆Tx）。

串行通信处于活动状态时，可以将引脚0和1用作输入吗？

如果是，则必须是以下代码：

/*     SparkFun Keypad Pinout:
       Rows and columns are connected as such:
       -------------
     R1  | 1 | 2 | 3 | - 5 (grün)
     R2  | 4 | 5 | 6 | - 0 (braun)
     R3  | 7 | 8 | 9 | - 1 (schwarz)
     R4  | * | 0 | # | - 3 (violett)
       -------------
           |C1 |C2 |C3
     4(blau) 6(gelb) 2(weiß)
    */
    // Pins 1-7 of the keypad connected to the Arduino respectively:
    int keypadPins[7] = {0, 1, 2, 3, 4, 5, 6};
    int keypadStatus;  // Used to monitor which buttons are pressed.
    int timeout;  // timeout variable used in loop
    
    void setup()
    {
      Serial.begin(9600);
      for (int i=0; i<7; i++)
      {
        pinMode(keypadPins[i], INPUT);  // Set all keypad pins as inputs
        digitalWrite(keypadPins[i], HIGH);  // pull all keypad pins high
      }
    }
    
    void loop()
    {
      keypadStatus = getKeypadStatus();  // read which buttons are pressed
      if (keypadStatus != 0)  // If a button is pressed go into here
      {
        sendKeyPress(keypadStatus);  // send the button over USB
        timeout = 2000;  // top of the repeat delay
        while ((getKeypadStatus() == keypadStatus) && (--timeout))  // Decrement timeout and check if key is being held down
          delayMicroseconds(1);
        while (getKeypadStatus() == keypadStatus)  // while the same button is held down
        {
          sendKeyPress(keypadStatus);  // continue to send the button over USB
          delay(50);  // 50ms repeat rate
        }
      }
    }
    
    /* sendKeyPress(int key): This function sends a single key over USB
       It requires an int, of which the 12 LSbs are used. Each bit in
       key represents a single button on the keypad.
       This function will only send a key press if a single button
       is being pressed */
    void sendKeyPress(int key)
    {
      switch(key)
      {
        case 1:  // 0x001
          Serial.print('1');  // Sends a keyboard '1'
          break;
        case 2:  // 0x002
          Serial.print('2');
          break;
        case 4:  // 0x004
          Serial.print('3');
          break;
        case 8:  // 0x008
          Serial.print('4');
          break;
        case 16:  // 0x010
          Serial.print('5');
          break;
        case 32:  // 0x020
          Serial.print('6');
          break;
        case 64:  // 0x040
          Serial.print('7');
          break;
        case 128:  // 0x080
          Serial.print('8');
          break;
        case 256:  // 0x100
          Serial.print('9');
          break;
        case 512:  // 0x200
          Serial.print('*');
          break;
        case 1024:  // 0x400
          Serial.print('0');  // Sends a keyboard '0'
          break;
        case 2048:  // 0x800
          Serial.print('\n');  // Sends the 'ENTER' key
          break;
      }
    }
    
    /* getKeypadStatus(): This function returns an int that represents
    the status of the 12-button keypad. Only the 12 LSb's of the return
    value hold any significange. Each bit represents the status of a single
    key on the button pad. '1' is bit 0, '2' is bit 1, '3' is bit 2, ..., 
    '#' is bit 11.
    
    This function doesn't work for multitouch.
    */
    int getKeypadStatus()
    {
      int rowPins[4] = {keypadPins[5], keypadPins[0], keypadPins[1], keypadPins[3]};  // row pins are 5, 0, 1, and 3 of the keypad
      int columnPins[3] = {keypadPins[4], keypadPins[6], keypadPins[2]};  // column pins are pins 2, 4, and 6 of the keypad
      int keypadStatus = 0;  // this will be what's returned
      
      /* initialize all pins, inputs w/ pull-ups */
      for (int i=0; i<7; i++)
      {
        pinMode(keypadPins[i], INPUT);
        digitalWrite(keypadPins[i], HIGH);
      }
      
      for (int row=0; row<4; row++)
      {  // initial for loop to check all 4 rows
        pinMode(rowPins[row], OUTPUT);  // set the row pin as an output
        digitalWrite(rowPins[row], LOW);  // pull the row pins low
        for (int col=0; col<3; col++)
        {  // embedded for loop to check all 3 columns of each row
          if (!digitalRead(columnPins[col]))
          {
            keypadStatus |= 1 << ((row+1)*3 + (col+1) - 4);  // set the status bit of the keypad return value
          }
        }
        pinMode(rowPins[row], INPUT);  // reset the row pin as an input
        digitalWrite(rowPins[row], HIGH);  // pull the row pin high
      }
      
      return keypadStatus;
    }