EDIT: I am using this for programming a pic, so the C will be quite limited. The compiler is XC8.

Following function expects me to pass a string:

void OLED_string(char* str, short x, short y) {

    short pos = 0;
    char character = str[pos++];
    short startx = x;
    short starty = y;
    while(character != '\0') {
        OLED_char(character, startx, starty);
        if(startx >= 123) starty++; //wrap around
        startx += 5;
        character = str[pos++];

I would like to display a value I have in a unsigned Integer. This value should be converted to Float and then divided by ten. Since float is very slow I would prefer to convert the integer to a string, and then simply add a point before the last character. I tried to pass directly the integer to this function but it does not work. Thanks!

  • \$\begingroup\$ This is straight c. It would fit better in stack overflow. \$\endgroup\$ May 2, 2015 at 21:23
  • \$\begingroup\$ Well, its the code for a microcontroller programmed with mplab and xc8 compiler. People in this forum have a better specific knowledge as this c is quite limited if compared to the full C that the guys over there are used to.. \$\endgroup\$ May 2, 2015 at 22:24

4 Answers 4


If you can use C standard library functions, sprintf() should handle the string conversion. Instead of adding the decimal point by shuffling characters around, you could use integer arithmetic:

char str[20];
unsigned int value = 105;

sprintf(str, "%u.%u", value / 10, value % 10);

Integer division won't be fast, but it should be faster than floating point. And I suspect that the int -> string conversion algorithm will be doing division anyway.

  • \$\begingroup\$ snprintf version is better as it limits buffer usage. \$\endgroup\$
    – Ayhan
    May 2, 2015 at 22:07
  • \$\begingroup\$ Thanks! Will this work in mplab with xc8 compilrr? \$\endgroup\$ May 2, 2015 at 22:28
  • \$\begingroup\$ It should. This is ANSI-standard C. \$\endgroup\$
    – Adam Haun
    May 2, 2015 at 22:37

The itoa function is your friend. http://www.cplusplus.com/reference/cstdlib/itoa/

  • \$\begingroup\$ Thanks, but im not sure that this is supported by the xc8 compiler.. \$\endgroup\$ May 2, 2015 at 22:31
  • \$\begingroup\$ can you just try it out? \$\endgroup\$ May 2, 2015 at 22:34

itoa and ftoa functions are both in stdlib.h in XC8 compiler so they will work on PIC. Just include <stdlib.h>


ITOA bei XC8:

int main(void) {
  char Buffer[7];
  int i = 12345;
  itoa(Buffer, i, 10);

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