Conversion of string to int

Projects Programming
1

Hi everyone! Thank you for your help!

I can't understand how to convert a string to an int value.

This

pos = stringa.toInt();

returns 0 even if stringa contains "180" (actually

Serial.println(stringa); 

prints "180" on the serial monitor).

Here is the complete code.

#include <Servo.h>

Servo myservo; 

int pos = 0; 
int servoPin = 3;
String stringa;

void setup() {

Serial.begin(9600);

myservo.attach(servoPin); 
myservo.write(0);
}

void loop() {

while (Serial.available()) 
    {
    Serial.println("Available");
    Serial.println(Serial.readString());
    stringa = Serial.readString();
    Serial.println(stringa);    
    pos = stringa.toInt();  
    Serial.println(pos);
    myservo.write(pos);
  }
}
2

1. Use atoi() function to convert a string into integer.

2. Example (I have used blocking instruction with 1-sec default timeout option.)
(1) Upload the following sketch.

char myData[20];

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

void loop() 
{
  byte n = Serial.available();
  if( n!=0)
  {
    byte m = Serial.readBytesUntil('\n', myData, 20);
    myData[m] = '\0';  //insert null charcater
    int x = atoi(myData); //converts string to int
    Serial.println(x);    //shows 180
  }
}

(2) Bring the Serail Monitor (Fig-1) with Bd = 9600 and 'Line ending tab' at 'No line ending' option.
(3) Enter 180 in the InputBox of the Serial Monitor (Fig-1) and click on the Send button.

SerialMonitorX.png
SerialMonitorX.png746×474 33.6 KB

Figure-1:

(4) Check that 180 has appeared on the OutputBox of Serial Monitor (Fig-2).
smy.png
Figure-2:

SerialMonitorX.png
SerialMonitorX.png746×474 33.6 KB

smy.png

3 
    Serial.println(Serial.readString());
    stringa = Serial.readString();

You are reading the String twice. The first one removes it from the buffer so the second one fails

4

UKHeliBob:

    Serial.println(Serial.readString());

stringa = Serial.readString();



You are reading the String twice. The first one removes it from the buffer so the second one fails

Ok, thank you! Actually that was the problem; now it works!

5

GolamMostafa:
1. Use atoi() function to convert a string into integer.

2. Example (I have used blocking instruction with 1-sec default timeout option.)
(1) Upload the following sketch.

char myData[20];

void setup()
{
 Serial.begin(9600);
}

void loop()
{
 byte n = Serial.available();
 if( n!=0)
 {
   byte m = Serial.readBytesUntil('\n', myData, 20);
   myData[m] = '\0';  //insert null charcater
   int x = atoi(myData); //converts string to int
   Serial.println(x);    //shows 180
 }
}



**(2)** Bring the Serail Monitor (Fig-1) with Bd = 9600 and 'Line ending tab' at 'No line ending' option.
**(3)** Enter 180 in the InputBox of the Serial Monitor (Fig-1) and click on the Send button.
![SerialMonitorX.png|746x474](upload://ekt4vqUAiGFuKMULT7uTZHW7sHg.png)
Figure-1:

**(4)** Check that 180 has appeared on the OutputBox of Serial Monitor (Fig-2).
![smy.png|647x482](upload://4LDFNa1hd0gCXgjSDEyuNxSAh8S.png)
Figure-2:

I'll try any way!

But what about int()?

6

salventre:
But what about int()?

int() is used to cast data types and not convert from one data type to another.

7

toInt() method is not recommended as it uses String class which causes memory fragmentation in AVR MCUs.

8

Actually that was the problem

I know. That is why I pointed it out

9

Danois90:
int() is used to cast data types and not convert from one data type to another.

Sorry, what does that mean?

10

salventre:
Sorry, what does that mean?

This is a cast:

float number = 123.54;
int casted_to_int_1 = int(number); //123
int casted_to_int_2 = (int)number; //123
int rounded_to_int = round(number); //124

You cannot cast from a string representation of a number to a numeric value since this operation requires a conversion.