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C Function to convert string to upper case


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Trying to create C function to convert a String ASCII to upper case.

This is what I tried and it does not work:

static void PrefixToUpper(volatile char* Prefix, int PrefixLen)
{
    // User code starts below this comment
    for (int i  = 0; Prefix[i] != '\0' ; i++)
        {
        if(Prefix[i] >= 'a' && Prefix[i] <= 'z')
                {
                    Prefix[i] = Prefix[i] - 32;
                }
        }
    // User code ends above this comment
}

// User code starts below this comment

Tested the code in C compiler and it runs correctly:

static void PrefixToUpper(volatile char* Prefix)
{
    // User code starts below this comment
    for (int i  = 0; Prefix != '\0' ; i++)
        {
        if(Prefix >= 'a' && Prefix <= 'z')
                {
                    Prefix = Prefix - 32;
                }
        }
    // User code ends above this comment
}

int main() 
   {
   char str[] = "hmh00234";
    
   printf("String input: %s\n", str);
   PrefixToUpper(str);
   printf("String output: %s\n", str);
   }
 

 

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OK, if you are sure that the ladder code that you've shown me is being executed, then I have no idea why it doesn't work.

I could debug it better if I had the project.

You can also debug it by putting in increment after the PrefixToUpper, so you can see with Online debug (or with HMI element) that the number is being incremented (and it should increment only once). You can also store Prefix Tractor Serial No into another string tag, so you could see its value after the function was called.

 

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