Modjo String problem

Another issue that i found, create a String object with a float (for example String(3.32)) different from 0 stop the program. If someone can test it please ? For information, i have the lasted arduino library (udoo).

 

Can you give us more info @modjo?

 

Yes, simply if i create a String object form a float that is equal to zero the sketch run :

Code:

float myFloat=0;
String data =String(myFloat);

But if i define this (or modify the value of the float later--> from adc for example) the sketch compile but the program stop or bug in the card :

Code:

float myFloat=3.14;
String data =String(myFloat);

 

I still don't understand your problem. What do you want to achieve? How is UDOO related to this problem?
EDIT: Take a look, this may help http://forum.arduino.cc/index.php?topic=243660.0

 

I'm not a C++ programmer by heart, but afaik there is no float constructor of a string , is there? If you initialize it with 0 I guess it will create a string solely of '\0' aka The Empty String. if you pass 3.14 it will pass it some string starting with character nonsense until somewhere in the memory it will encounter a \0.

The C++ library seems to contain a to_string method, which might have the function you need. See the C++ reference: http://www.cplusplus.com/reference/string/to_string/

(I have no idea of which version/subset of C++ UDOO/Arduino is delivering)

 

I just want to create a string with a float because i can't send a structure for the moment over serial, see this issue :
http://www.udoo.org/forum/threads/bug-with-uart-com.4499/
Otherwise, i just want to use a constructor of Arduino String object that take float in argument ! see here for more details :
https://www.arduino.cc/en/Tutorial/StringConstructors
I'm not a fan of string use in programming (take more time to process !!!), but for the moment it's the easiest way to use serial com with A9 (send a packed struct not working ....)

 

Have you tested the float constructor on a standard Arduino?
What about using something like snprintf? http://maxsi.org/coding/c-string-creation.html

 

snprintf is out. The following code crashes the M4:

Code:

double x = 1234.56;
char buf[128];
snprintf(buf, 128, "%f", x);

 

Okay guys, I came up with a solution that has worked for me so far. I modified the printFloat function from AppData\Local\Arduino15\packages\UDOO\hardware\solox\1.6.7\variants\udooneo\Print.cpp to write a double to a char* buffer, which was exactly what I needed. Leaving it here in case anyone finds it useful:

[Edit: Modified to return pointer to buffer.]

Code:

char *doubleToString(double number, uint8_t digits, char *buffer, int bufferLength) {
    int bufIndex = 0;

    if (isnan(number)) {
        snprintf(buffer, bufferLength, "nan");
        return buffer;
    }

    if (isinf(number)) {
        snprintf(buffer, bufferLength, "inf");
        return buffer;
    }

    if (number > 4294967040.0) {
        snprintf(buffer, bufferLength, "ovf");
        return buffer;
    }

    if (number <-4294967040.0) {
        snprintf(buffer, bufferLength, "ovf");
        return buffer;
    }

    // Handle negative numbers
    if (number < 0.0) {
        buffer[bufIndex++] = '-';
        number = -number;
    }

    // Round correctly so that print(1.999, 2) prints as "2.00"
    double rounding = 0.5;
    for (uint8_t i = 0; i < digits; ++i) {
        rounding /= 10.0;
    }
    number += rounding;

    // Extract the integer part of the number and print it
    unsigned long int_part = (unsigned long)number;
    double remainder = number - (double)int_part;
   
    char tmp[bufferLength];
    itoa (int_part, tmp, 10);
    for (int i = 0; i < strlen(tmp); i++) {
        buffer[bufIndex++] = tmp[i];
    }

    // Print the decimal point, but only if there are digits beyond
    if (digits > 0) {
        buffer[bufIndex++] = '.';
    }

    // Extract digits from the remainder one at a time
    while (digits-- > 0) {
        remainder *= 10.0;
        int toPrint = int(remainder);
        itoa (toPrint, tmp, 10);
        buffer[bufIndex++] = tmp[0];
        remainder -= toPrint;
    }

    //Null-terminate the string
    buffer[bufIndex] = '\0';

    return buffer;
}

Usage:

Code:

    double x = -1234.5678;
    char buf[128];
    doubleToString(x, 2, buf, 128);
    Serial0.println(buf);

 

@Andrea Rovai , it would be great to integrate this into the official udoo arduino lib i think !

 

Not if it then deviates from the standard Arduino libraries.