How to Convert Char to Int in Arduino

Converting a char to an int is common in Arduino programming. It allows you to manipulate and perform mathematical operations on character data.

This tutorial will discuss six methods to convert a char into an int in Arduino.

Use the atoi() Function to Convert char to int in Arduino

The atoi() function is a standard C library function that converts a string (character array) containing numerical representation into its integer equivalent.

void setup() {
  Serial.begin(9600);

  char charValue[] = "1234";
  int intValue = atoi(charValue);

  Serial.println(intValue);
}

void loop() {
  // Your code here
}

1. void setup() { ... }: This is the setup function, where you initialize your code. We start the serial communication at a baud rate of 9600.
2. char charValue[] = "1234";: This line initializes a character array charValue with the value "1234".
3. int intValue = atoi(charValue);: Here, we use the atoi() function to convert the character array charValue to an integer intValue.
4. Serial.println(intValue);: This line prints the converted integer value to the serial monitor.

Output:

1234

Use ASCII Values to Convert char to int in Arduino

This method can only convert a single char into an int. You must subtract a zero of type char from the char to convert it into an int.

This method exploits the ASCII values to convert characters to integers.

void setup() {
  Serial.begin(9600);

  char charValue = '5';
  int intValue = charValue - '0';

  Serial.println(intValue);
}

void loop() {
  // Your code here
}

1. void setup() { ... }: Similar to the previous method, this is the setup function where we initialize serial communication.
2. char charValue = '5';: This line initializes a character variable charValue with the value '5'.
3. int intValue = charValue - '0';: Here, we subtract the ASCII value of '0' from the ASCII value of charValue. This converts the character '5' to its integer value 5.
4. Serial.println(intValue);: This line prints the converted integer value to the serial monitor.

Output:

5

Use Type Casting to Convert char to int in Arduino

Type casting involves explicitly changing the data type of a variable. In this case, we cast a character to an integer.

void setup() {
  Serial.begin(9600);

  char charValue = '7';
  int intValue = int(charValue - '0');

  Serial.println(intValue);
}

void loop() {
  // Your code here
}

1. void setup() { ... }: As before, this is the setup function where we initialize serial communication.
2. char charValue = '7';: This line initializes a character variable charValue with the value '7'.
3. int intValue = int(charValue - '0');: Here, we use type casting to convert the result of charValue - '0' to an integer.
4. Serial.println(intValue);: This line prints the converted integer value to the serial monitor.

Output:

7

Use the toInt() Function to Convert char to int in Arduino

To use the toInt() function to convert a char to an int in Arduino, you’ll first need to convert the char to a String and then use the toInt() function.

void setup() {
  Serial.begin(9600);

  char charValue = '7';
  String stringValue(charValue);
  int intValue = stringValue.toInt();

  Serial.println(intValue);
}

void loop() {
  // Your code here
}

1. void setup() { ... }: This is the setup function where we initialize serial communication.
2. char charValue = '7';: This line initializes a character variable charValue with the value '7'.
3. String stringValue(charValue);: Here, we create a String object named stringValue by passing the charValue to the constructor. This converts the char to a String.
4. int intValue = stringValue.toInt();: We then use the toInt() function to convert the String object to an integer. The resulting integer value is stored in intValue.
5. Serial.println(intValue);: This line prints the converted integer value to the serial monitor.

Output:

7

Use the sscanf() Function to Convert char to int in Arduino

The sscanf() function reads the buffered data based on the specified format.

Syntax:

sscanf(char *data, char *format, [&var1, &var2, ... ]);

Where:

1. *data is the pointer to the array.
2. *format is the sequence of characters specifying how the data shall be interpreted.
3. &var1,... is the additional argument specifying the location to save the extracted data.

We can use the below code to read the char to int.

sscanf(someChar, "%d", &result);

Here, %d specifies that the char shall be read as a signed integer decimal.

The complete Arduino code to convert char to int is below.

void setup() {
  Serial.begin(9600); /*Serial Communication begins*/
  char *someChar = "50";
  int result = 0;

  sscanf(someChar, "%d", &result);

  Serial.println(result);
}

void loop() {}

Output:

50

Use the Serial.parseInt() Function to Convert char to int in Arduino

You can use this method if you are reading input from a serial port of an Arduino and want to convert the received input into an Int.

void loop() {
  if (Serial.available() > 0) {
    int valA = Serial.parseInt();
  }
}

Parsing will stop if no value has been read or a non-digit is read. If no valid input is read until timeout, then 0 will be returned.

See Serial.setTimeout() to set the timeout of the serial. Check this link for more information about the Serial.parseInt() function.

Conclusion

In this tutorial, we’ve explored six methods to convert a char to an int in Arduino. Each method has its advantages and use cases, so choose the one that best suits your application.

Understanding these methods will give you greater flexibility in handling character data in your Arduino projects.