Converting a string to int in arduino?

Projects Programming
1

Hello, sorry if this is a bit of a noob question, relatively new to c++ and the arduino language.

Basically, I'm trying to convert the string amount from the array infoArray into an int in order to run the for loop below. (if I don't convert to int, it tells me that i isn't defined. I think that's the issue?) I know that infoArray[2] is always a one digit number as a string.

I've tried the function toInt() but it gives me the error below:

request for member 'toInt' in 'amount', which is of non-class type 'int'

Thank you for your help

void dispenser(){
  amount = infoArray[2];
  
  for (i=amount; i>0; i--){
    servo.write(60);
    delay(1000);
    servo.write(0);
    delay(1000);
  }
  Serial.println("very good");
}
2

Wen you post code can you please post all of it. Most of the time when you only post a snippet the problem is elsewhere.

3

Use

amount = atoi(infoArray);

Or

If always absolutely that true,

amount = infoArray[0] - '0';
4

You can’t have a one digit number as a string. You need at least two bytes for a string.
Is it an ASCII char?
If so turn it into a number by
number = digit & 0xF;

5

Hi. Thanks for your help. Just to clarify, infoArray would looks something like {'g', '2', '3', ' '}, so converting the entire array through atoi wouldn't work. (I think that's what snippet #1 meant?)

Also, can you please explain what the second snippet (amount = infoArray[0] - '0') is doing?
Thank you

6

Hi. So regarding the entire code, I'm on vacation and don't have it at the moment, but everything else worked fine, I've only started running into issues with this function. A basic run through of the program would be the arduino receives a string through serial, and then takes each character and puts them into an array. Then it would perform certain actions based on what numbers/characters are where.

For your second post, yes, I realized that the array wasn't a string and an ascii char instead, but when I tried yours and chrisnightley's solutions, the program returned that i in the for loop wasn't defined, which tells me that amount wasn't actually converted to an int. (I think?)

Thanks for your help

7

Forget it, if that condition.

Subtract '0'(character) from '0'(character) to get 0 (number).
Subtract '0'(character) from '1'(character) to get 1 (number).
Subtract '0'(character) from '2'(character) to get 2 (number).
Subtract '0'(character) from '3'(character) to get 3 (number).
... to 9

See ASCII code for more realization.

This will work.

char infoArray[] = {'g', '2', '5', '9'};
int amount1 = infoArray[1]-'0'; // assign numerical 2
int amount2 = infoArray[2]-'0'; // assign numerical 5
int amount3 = infoArray[3]-'0'; // assign numerical 9
8

Hi. That was a good explanation and the code did the trick, thank you!

9

My second solution was exactly the same as @chrisknightley
So what ever was wrong it is not what I told you to do. It was probably that you had not implemented it correctly, I just gave you and example using variables that reflected what you needed to do.
If you had not declared ’amount’ as a variable previously in your code and used i as the loop variable then yes you will get an error saying the variable i was not declared.

& 0xF Has exactly the same effect as - '0'

10

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