Converting string to int in arduino

Question

An error has popped up for my if statement and I need YOUR help to fix it the error says invalid cast from type String to type int.

int inputPin = 8;
int pirState = LOW;
int val = 0;
int counter = 0;
String temp_obj;

#include <Wire.h>
#include <Adafruit_MLX90614.h>
#include <LiquidCrystal_I2C.h>

Adafruit_MLX90614 mlx = Adafruit_MLX90614();

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  temp_obj = mlx.readObjectTempC();
  mlx.readObjectTempC()
  temp_obj = temp_obj.substring(5, 6);
  lcd.begin();
  lcd.backlight();
  pinMode(inputPin, INPUT);
  Serial.begin(9600);
  mlx.begin();
}

void loop() {
  val = digitalRead(inputPin);
  if (val == HIGH) {
    Serial.print("Tem ");
    Serial.print(mlx.readObjectTempC());
    Serial.println(" Celsius");
    lcd.setCursor(0, 0);
    lcd.print("temperature");
    lcd.print(mlx.readObjectTempC());
    counter = counter + 1;
    delay(90);
    temp_obj = temp_obj.substring(0);
    Serial.println(temp_obj);
  }
}

void kaiguan() {
  if (pirState == LOW) {
    Serial.println("Motion detected!");
    pirState = HIGH;
    Serial.println(mlx.readObjectTempC());
    if (int(temp_obj) < 30) {
      //an error has popped up for my if statement and I need YOUR help to fix it the error says invalid cast from type String to type int.
      lcd.setCursor(0, 1);
      lcd.print(temp_obj);
      lcd.setCursor(0, 2);
      lcd.print("Not detected,reset!");
    }
  }
}

@TedLyngmo - Hey I'm kind of new to editing, and I guess you were at the same time that I was - but I formatted the code with proper spacing and whatnot - and it told me I needed to explain my edit - and so I did that both in the post and the edit summary - after refreshing from your edit - but it would not let me post. Any idea why? I'm not sure what I've done wrong. — user3546408
– user3546408, Commented Aug 4, 2021 at 0:40
The point is, have you searched "arduino String to int"? The very first hit is the Arduino documentation for toInt — kaylum
– kaylum, Commented Aug 4, 2021 at 0:42

HiEd · Accepted Answer · 2021-08-04 05:21:10Z

1

Change

int(temp_obj)

to

temp_obj.toInt()

You can read more about the function in the official doc as pointed out in the comment.

answered Aug 4, 2021 at 5:21

HiEd

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