Arduino C/C++ Convert binary string to decimal

Question

I wanted to post this on the Arduino forum but couldn't find any "new post" button...
Anyway, I wrote this function to convert a binary string into an int/long.
However, it doesn't always work with big numbers.

The following code is supposed to return "888888" but returns "888.887"

void setup() {
  Serial.begin(9600);
  String data = "11011001000000111000"; //888888
  Serial.print(binStringToInt(data));
}

unsigned long binStringToInt(String bin) {
  unsigned long total = 0;
  int binIndex = 0;
  for (int i = bin.length() - 1; i > - 1; i--) {
    total += round(pow(2, binIndex)) * (bin.charAt(i) - '0');
    binIndex++;
  }
  return total;
}

pow usually returns a floating type. Have you tried another method, for example bitwise shift? — Tobias Fendin
– Tobias Fendin, Commented Feb 5, 2021 at 8:56
Common misunderstanding: the StackExchange sites are not classical forums. They are Q&A sites. You post a "new question", but you need to have an account. — the busybee
– the busybee, Commented Feb 5, 2021 at 11:56

Silidrone · Accepted Answer · 2021-02-05 09:06:12Z

1

You can use a simpler function to achieve that:

long binary_to_int(char *binary_string){
    long total = 0;
    while (*binary_string)
    {
     total *= 2;
     if (*binary_string++ == '1') total += 1;
    }
    
    return total;
}

void setup(){
    Serial.begin(9600);
    String data = "11011001000000111000";
    Serial.print(binary_to_int(data.c_str())); // prints 888888
}

I used.c_str() to get a char * to Arduino String.

edited Feb 5, 2021 at 9:06

answered Feb 5, 2021 at 8:59

Silidrone

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0___________ · Accepted Answer · 2021-02-05 09:04:48Z

1

When programming Arduino rather forget about String and vectors, use C strings and C arrays as it is very resources limited.
Never use floats and float functions when dealing with integers.

unsigned long long convert(const char *str)
{
    unsigned long long result = 0;

    while(*str)
    {
        result <<= 1;
        result += *str++ == '1' ? 1 : 0;
    }
    return result;
}

answered Feb 5, 2021 at 9:04

0___________

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