将单个字符串/字符输入串行监视器

Question

我在将字符串/字符输入串行监视器时遇到问题，我是编程初学者，因此不知道如何解决。

我有一个 if/else 语句，它的作用类似于 switch case 语句。我确实从一个 switch case 开始，但我遇到了很多问题，其中一个是输入一个字符串/字符（A、S、M、D、P）来指向每个 case。我知道 switch case 是针对 int 的，所以我放弃了，转而使用多个 if/else 语句。

我已经尝试过（在 void loop() 中），

char theOperator = dataInput();

if (theOperator == 'A') {
  // If input is equal to 1, carry out function 'addition()'
  addition();
}

但它会显示我在“添加”函数中的错误消息。

这里是使用输入代码的地方（全局定义），

char theOperator;

char dataInput() {
  while (!Serial.available()) {
    // Wait for the user to enter value
  }
  return Serial.parseInt();
}

我尝试过类似 Serial.read() 之类的东西，但这要么循环我的程序的开头并且不允许我输入值，要么根本不接受值。

任何帮助将不胜感激，我将在下面发布我的完整代码，以便您了解我的程序（if/else 等问题在顶部）。

*编辑：忘了说，我可以做类似的事情，

char theOperator = dataInput();

  if (theOperator == 1) {
    // If input is equal to 1, carry out function 'addition()'
    addition();
  }

这很有效。但是我希望它取 A、S、M、D 或 P 而不是 1、2、3、4、5。

#define LED_RED 5
#define LED_ORANGE 6
#define LED_YELLOW 9
#define LED_GREEN 10
#define LED_BLUE 11

int potValue;

#define potPin A0

// Limits the range of the numbers entered to between -99 and 999
long firstNumber = constrain(firstNumber, -99, 999);
long secondNumber = constrain(secondNumber, -99, 999);
long value;

char theOperator;

char dataInput() {
  while (!Serial.available()) {
    // Wait for the user to enter value
  }
  return Serial.parseInt();
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void setup() {

  Serial.begin(9600);

  pinMode(LED_RED, OUTPUT);
  pinMode(LED_ORANGE, OUTPUT);
  pinMode(LED_YELLOW, OUTPUT);
  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_BLUE, OUTPUT);

  pinMode(potPin, INPUT);
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void loop() {

  Serial.println ("Enter your chosen operator");
  Serial.println ("A for Addition, S for Subtraction, M for Multiplication,");
  Serial.println ("D for Division, and P for Potentiometer: ");

  // Takes an input from the user
  char theOperator = dataInput();

  if (theOperator == 'A') {
    // If input is equal to 1, carry out function 'addition()'
    addition();
  }
  else if (theOperator == 'S') {
    // If input is equal to 2, carry out function 'subtraction()'
    subtraction();
  }
  else if (theOperator == 'M') {
    // If input is equal to 3, carry out function 'multiplication()'
    multiplication();
  }
  else if (theOperator == 'D') {
    // If input is equal to 4, carry out function 'division()'
    division();
  }
  else if (theOperator == 'P') {
    // If input is equal to 5, carry out function 'potentiometer()'
    potentiometer();
  }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void addition() {

  Serial.println ("A");
  Serial.println ("Please enter first number in format nnn: ");
  firstNumber = dataInput(); // Asks the user to input the first set of numbers

  /* Message must be in format cnnnnnn
     therefore first number must be greater than or equal to -99 and less than or equal to 999*/
  if (firstNumber >= -99 && firstNumber <= 999) {
    Serial.println (firstNumber); // Prints the first set of numbers for the user to view
  }
  else {
    /* If the data input does not match the format cnnnnnn then this error message will display
       if the input is invalid the red LED will also turn on */
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  Serial.println ("Please enter second number in format nnn: ");
  secondNumber = dataInput(); // Asks the user to input the second set of numbers

  /* Message must be in format cnnnnnn
     therefore second number must be greater than or equal to -99 and less than or equal to 999*/
  if (secondNumber >= -99 && secondNumber <= 999) {
    // The LED will turn off if it was previously on because this is a valid input
    digitalWrite(LED_RED, LOW);
    Serial.println (secondNumber); // Prints the second set of numbers for the user to view
  }
  else {
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  /* Give time for the red error LED to stay on
     for the user to notice he/she has made an invalid input */
  delay(500);
  digitalWrite(LED_RED, LOW);

  // As this case is for addition, it will add the first and second numbers
  value = (firstNumber + secondNumber);

  Serial.print("Value: ");
  // Prints the value of the two sets of numbers so that the user can see the value of their message
  Serial.println(value);

  /////// The 'sign' flag ///////
  if (value >= 1) {
    // If value is a positive number (excluding 0) turn orange LED on
    digitalWrite(LED_ORANGE, HIGH);
  }
  else if (value <= -1) {
    // If value is a negative number, turn orange LED off
    digitalWrite(LED_ORANGE, LOW);
  }
  else if (value == 0) {
    // If value is equal to 0, set orange LED at half brightness
    int brightness;
    // Changes the brightness of the LED so that it is half bright
    brightness++;
    brightness %= 128;
    analogWrite(LED_ORANGE, brightness);
  }

  /////// The 'even' flag ///////
  if ((value % 2) == 0) {
    // If the modulo is equal to 0, it's an even
    digitalWrite(LED_BLUE, HIGH);
  } else {
    // If the modulo is not equal to 0, it's an odd
    digitalWrite(LED_BLUE, LOW);
  }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void subtraction() {

  Serial.println ("S");
  Serial.println ("Please enter the first number in format nnn: ");
  firstNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore first number must be greater than or equal to -99 and less than or equal to 999*/
  if (firstNumber >= -99 && firstNumber <= 999) {
    Serial.println (firstNumber); // Prints the first set of numbers for the user to view
  }
  else {
    /* If the data input does not match the format cnnnnnn then this error message will display
       if the input is invalid the red LED will also turn on */
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  Serial.println ("Please enter second number in format nnn: ");
  secondNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore second number must be greater than or equal to -99 and less than or equal to 999*/
  if (secondNumber >= -99 && secondNumber <= 999) {
    digitalWrite(LED_RED, LOW);
    Serial.println (secondNumber); // Prints the second set of numbers for the user to view
  }
  else {
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  /* Give time for the red error LED to stay on
     for the user to notice he/she has made an invalid input */
  delay(500);
  digitalWrite(LED_RED, LOW);

  // As this case is for subtraction, it will subtract the first and second numbers
  value = (firstNumber - secondNumber);
  Serial.print("Value: ");
  // Prints the value of the two sets of numbers so that the user can see the value of their message
  Serial.println(value);

  /////// The 'sign' flag ///////
  if (value >= 1) {
    // If value is a positive number (excluding 0) turn orange LED on
    digitalWrite(LED_ORANGE, HIGH);
  }
  else if (value <= -1) {
    // If value is a negative number, turn orange LED off
    digitalWrite(LED_ORANGE, LOW);
  }
  else if (value == 0) {
    // If value is equal to 0, set orange LED at half brightness
    int brightness;
    // Changes the brightness of the LED so that it is half bright
    brightness++;
    brightness %= 128;
    analogWrite(LED_ORANGE, brightness);
  }

  /////// The 'even' flag ///////
  if ((value % 2) == 0) {
    // If the modulo is equal to 0, it's an even
    digitalWrite(LED_BLUE, HIGH);
  } else {
    // If the modulo is not equal to 0, it's an odd
    digitalWrite(LED_BLUE, LOW);
  }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void multiplication() {

  Serial.println ("M");
  Serial.println ("Please enter the first number in format nnn: ");
  firstNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore first number must be greater than or equal to -99 and less than or equal to 999*/
  if (firstNumber >= -99 && firstNumber <= 999) {
    Serial.println (firstNumber); // Prints the first set of numbers for the user to view
  }
  else {
    /* If the data input does not match the format cnnnnnn then this error message will display
       if the input is invalid the red LED will also turn on */
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  Serial.println ("Please enter second number in format nnn: ");
  secondNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore second number must be greater than or equal to -99 and less than or equal to 999*/
  if (secondNumber >= -99 && secondNumber <= 999) {
    digitalWrite(LED_RED, LOW);
    Serial.println (secondNumber); // Prints the second set of numbers for the user to view
  }
  else {
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  /* Give time for the red error LED to stay on
     for the user to notice he/she has made an invalid input */
  delay(500);
  digitalWrite(LED_RED, LOW);

  // As this case is for multiplication, it will multiply the first and second numbers
  value = (firstNumber * secondNumber);
  Serial.print("Value: ");
  // Prints the value of the two sets of numbers so that the user can see the value of their message
  Serial.println(value);

  /////// The 'sign' flag ///////
  if (value >= 1) {
    // If value is a positive number (excluding 0) turn orange LED on
    digitalWrite(LED_ORANGE, HIGH);
  }
  else if (value <= -1) {
    // If value is a negative number, turn orange LED off
    digitalWrite(LED_ORANGE, LOW);
  }
  else if (value == 0) {
    // If value is equal to 0, set orange LED at half brightness
    int brightness;
    // Changes the brightness of the LED so that it is half bright
    brightness++;
    brightness %= 128;
    analogWrite(LED_ORANGE, brightness);
  }

  /////// The 'even' flag ///////
  if ((value % 2) == 0) {
    // If the modulo is equal to 0, it's an even
    digitalWrite(LED_BLUE, HIGH);
  } else {
    // If the modulo is not equal to 0, it's an odd
    digitalWrite(LED_BLUE, LOW);
  }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void division() {

  Serial.println ("D");
  Serial.println ("Please enter the first number in format nnn: ");
  firstNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore first number must be greater than or equal to -99 and less than or equal to 999
     Division by 0 is not allowed */
  if (firstNumber >= -99 && firstNumber <= 999 && firstNumber != 0) {
    Serial.println (firstNumber); // Prints the first set of numbers for the user to view
  }
  else if (firstNumber == 0) {
    /* If the data input does not match the format cnnnnnn or if the input is
       equal to 0 then this error message will display, and if the input is invalid
       the red LED will also turn on, or if the input equals to 0 the LED will flash
       and stay on at half brightness */
    blinkError();
    Serial.println ("--------------- ERROR ---------------");
  }
  else {
    digitalWrite(LED_RED, HIGH);
  }

  Serial.println ("Please enter second number in format nnn: ");
  secondNumber = dataInput();

  /* Message must be in format cnnnnnn
     therefore second number must be greater than or equal to -99 and less than or equal to 999
     Division by 0 is not allowed */
  if (secondNumber >= -99 && secondNumber <= 999 && secondNumber != 0) {
    digitalWrite(LED_RED, LOW);
    Serial.println (secondNumber); // Prints the second set of numbers for the user to view
  }
  else if (secondNumber == 0) {
    blinkError();
    Serial.println ("--------------- ERROR ---------------");
  }
  else {
    digitalWrite(LED_RED, HIGH);
    Serial.println ("--------------- ERROR ---------------");
  }

  /* Give time for the red error LED to stay on
     for the user to notice he/she has made an invalid input */
  delay(500);
  digitalWrite(LED_RED, LOW);

  // As this case is for division, it will divide the first and second numbers
  value = (firstNumber / secondNumber);
  Serial.print("Value: ");
  // Prints the value of the two sets of numbers so that the user can see the value of their message
  Serial.println(value);

  /////// The 'sign' flag ///////
  if (value >= 1) {
    // If value is a positive number (excluding 0) turn orange LED on
    digitalWrite(LED_ORANGE, HIGH);
  }
  else if (value <= -1) {
    // If value is a negative number, turn orange LED off
    digitalWrite(LED_ORANGE, LOW);
  }
  else if (value == 0) {
    // If value is equal to 0, set orange LED at half brightness
    int brightness;
    // Changes the brightness of the LED so that it is half bright
    brightness++;
    brightness %= 128;
    analogWrite(LED_ORANGE, brightness);
  }

  /////// The 'even' flag ///////
  if ((value % 2) == 0) {
    // If the modulo is equal to 0, it's an even
    digitalWrite(LED_BLUE, HIGH);
  } else {
    // If the modulo is not equal to 0, it's an odd
    digitalWrite(LED_BLUE, LOW);
  }
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void potentiometer() {

  Serial.println("P");

  do {
    if (potValue >= 0 && potValue <= 6) {
      /* If the value on the potentiometer is greater than or equal to 0,
         or less than or equal to 6, the red LED will turn on */

      potValue = analogRead(potPin); // Reads the value on the pin
      potValue = map(potValue, 0, 1023, 0, 31); // Changes the default range from 0 to 1023 to 0 to 31

      // Converts the DEC value of the potentiometer to BIN
      Serial.println(potValue, BIN);
      delay(500);

      digitalWrite(LED_RED, HIGH);
      digitalWrite(LED_ORANGE, LOW);
      digitalWrite(LED_YELLOW, LOW);
      digitalWrite(LED_GREEN, LOW);
      digitalWrite(LED_BLUE, LOW);
    }
    else if (potValue >= 7 && potValue <= 12) {
      /* If the value on the potentiometer is greater than or equal to 3,
         or less than or equal to 12, the orange LED will turn on */

      potValue = analogRead(potPin); // Reads the value on the pin
      potValue = map(potValue, 0, 1023, 0, 31); // Changes the default range from 0 to 1023 to 0 to 31

      Serial.println(potValue, BIN);
      delay(500);

      digitalWrite(LED_RED, LOW);
      digitalWrite(LED_ORANGE, HIGH);
      digitalWrite(LED_YELLOW, LOW);
      digitalWrite(LED_GREEN, LOW);
      digitalWrite(LED_BLUE, LOW);
    }
    else if (potValue >= 13 && potValue <= 18) {
      /* If the value on the potentiometer is greater than or equal to 13,
         or less than or equal to 18, the yellow LED will turn on */

      potValue = analogRead(potPin); // Reads the value on the pin
      potValue = map(potValue, 0, 1023, 0, 31); // Changes the default range from 0 to 1023 to 0 to 31

      Serial.println(potValue, BIN);
      delay(500);

      digitalWrite(LED_RED, LOW);
      digitalWrite(LED_ORANGE, LOW);
      digitalWrite(LED_YELLOW, HIGH);
      digitalWrite(LED_GREEN, LOW);
      digitalWrite(LED_BLUE, LOW);
    }
    else if (potValue >= 19 && potValue <= 24) {
      /* If the value on the potentiometer is greater than or equal to 19,
         or less than or equal to 24, the green LED will turn on */

      potValue = analogRead(potPin); // Reads the value on the pin
      potValue = map(potValue, 0, 1023, 0, 31); // Changes the default range from 0 to 1023 to 0 to 31

      Serial.println(potValue, BIN);
      delay(500);

      digitalWrite(LED_RED, LOW);
      digitalWrite(LED_ORANGE, LOW);
      digitalWrite(LED_YELLOW, LOW);
      digitalWrite(LED_GREEN, HIGH);
      digitalWrite(LED_BLUE, LOW);
    }
    else if (potValue >= 25 && potValue <= 31) {
      /*If the value on the potentiometer is greater than or equal to 25,
        or less than or equal to 31, the blue LED will turn on */

      potValue = analogRead(potPin); // Reads the value on the pin
      potValue = map(potValue, 0, 1023, 0, 31); // Changes the default range from 0 to 1023 to 0 to 31

      Serial.println(potValue, BIN);
      delay(500);

      digitalWrite(LED_RED, LOW);
      digitalWrite(LED_ORANGE, LOW);
      digitalWrite(LED_YELLOW, LOW);
      digitalWrite(LED_GREEN, LOW);
      digitalWrite(LED_BLUE, HIGH);
    }
  } while (true);
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void blinkError() {

  /////// The 'error' flag ///////

  int brightness = 0;

  // The for loop will loop 5 times
  for (int x = 0; x < 5; x++) {

    digitalWrite(LED_RED, HIGH);
    delay(100);
    digitalWrite(LED_RED, LOW);
    delay(100);

    // Changes the brightness of the LED so that it is half bright
    brightness++;
    brightness %= 128;
    analogWrite(LED_RED, brightness);
  }
}

Answer 1

在您的char dataInput() 函数中，您使用Serial.parseInt() 进行串行输入，当输入'A' parseInt 时将返回0。请参阅documentation。要读取字符，请使用 Serial.read() 获取单个字符。

void loop() {

  Serial.println ("Enter your chosen operator");
  Serial.println ("A for Addition, S for Subtraction, M for Multiplication,");
  Serial.println ("D for Division, and P for Potentiometer: ");

  // Takes an input from the user
  char theOperator = Serial.read();

  switch(theOperator) {
    case 'A':
    // If input is equal to 1, carry out function 'addition()'
      addition();
      break;
    case 'S':
    // If input is equal to 2, carry out function 'subtraction()'
      subtraction();
      break;
    case 'M':
    // If input is equal to 3, carry out function 'multiplication()'
      multiplication();
      break;
    case 'D':
    // If input is equal to 4, carry out function 'division()'
      division();
      break;
  case 'P':
    // If input is equal to 5, carry out function 'potentiometer()'
    potentiometer();
    break;
  }
}