F28035 sprintf doesn't work for floats

Yup KC1, I did notice the same thing few weeks ago when I needed sprintf for float to string conversion. It doesn't work! Also how do I limit my float's decimal numbers like %.2f in C (without using a math library)?

I would like one of my TI buddies to address this issue, why such limitation?

Regards,

Gautam

Ok, after some Googling around I found a solution.

Btw, sprintf did work for a normal project, but when I started from a CLA example, it didn't work.

I use the following code: (adapted from: http://stackoverflow.com/questions/2302969/how-to-implement-char-ftoafloat-num-without-sprintf-library-function-i) (Funny how it is from stackoverflow and I suspect this is a similar issue)

I have removed the exponent part.

Hope it helps!

#include <math.h>

#include <string.h>
// For printf

#include <stdio.h>

static double PRECISION = 0.001;

static int MAX_NUMBER_STRING_SIZE = 32; // this can be smaller I think

char print_str[30]; // this can be smaller I think

char text_1[30];

char * dtoa(char *s, double n) {

  // handle special cases

  if (isnan(n)) {

    strcpy(s, "nan");

  } else if (isinf(n)) {

    strcpy(s, "inf");

  } else if (n == 0.0) {

    strcpy(s, "0");

  } else {

    int digit, m, m1;

    char *c = s;

    int neg = (n < 0);

    if (neg)

      n = -n;

    // calculate magnitude

     m = log10(n);

    if (neg)

      *(c++) = '-';

    else

      // *(c++) = '+'; // To have a ‘+’ sign

    if (m < 1.0) {

      m = 0;

    }

    // convert the number

    while (n > PRECISION || m >= 0) {

      double weight = pow(10.0, m);

      if (weight > 0 && !isinf(weight)) {

        digit = floor(n / weight);

        n -= (digit * weight);

        *(c++) = '0' + digit;

      }

      if (m == 0 && n > 0)

        *(c++) = '.';

      m--;

    }

    *(c) = '\0';

  }

  return s;

}

int main(void){
  float num = 1.214;

  sprintf(text_1, “%s\n\r\0”, dtoa(print_str, num);
  scia_msg(text_1);

}

Hi,

sprintf(text_1, “%s\n\r\0”, dtoa(print_str, num);

KC1, the above method is for the ones who don't have libraries to play with. I was expecting the sprintf to function in this way:

double a = 0.0000005l;
char aa[50];
sprintf(aa,a);
sci_msg(aa);

It didn't work. Later found out that CCS supports the following pattern:

sprintf(char *_string, const char *_format, ...)

So, chose some other way to achieve the same!

Regards,

Gautam

Hi,

Yes it's for people who don't have standard C lib functions. But after using a CLA example project as a template, the sprintf function stopped working for converting floats to strings.

I googled around and saw that other people had similar issues and they had suspected it to be a stack problem. But it wasn't clear how to fix it. (Increasing stack size didn't work for me)

So I looked for a more efficient method and found the above code and it did the job for me.

Thanks.

Cool, no problem. Thanks for sharing!

Regards,

Gautam