Question

I’m trying to break down an integer with C on an 8-bit microcontroller (a PIC) into its ASCII equivalent characters.

For example:
convert 982 to ‘9’,’8′,’2′

Everything I’ve come up with so far seems pretty brute force. This is the main idea of what I’m basically doing right now:

if( (10 <= n) && (n < 100) ) {
// isolate and update the first order of magnitude
digit_0 = (n % 10);
// isolate and update the second order of magnitude
switch( n - (n % 10) ) {
  case 0:
    digit_1 = 0;
    break;
  case 10:
    digit_1 = 1;
    break;

…

And then I have another function to just add 0b00110000 (48decimal) to each of my digits.

I’ve been having trouble finding any C function to do this for me or doing it well myself.

Thanks in advance for any help!

Answer 1

To do it yourself you need to perform the operations which are demonstrated with the sample code below:

#include <stdio.h>

int main (void)
{
  unsigned int x = 512;
  int base_val = 10, digit, i = 0, n = 0;
  char x_str[32], t;

  printf ("\nEnter an unsigned number: ");
  scanf ("%u", &x);

  printf ("\nEnter base: ");
  scanf ("%d", &base_val);

  /* Chop the digits in reverse order and store in `x_arr`
   * the interpretation of the digits are made in base value
   * denoted by `base_val`
   */

  while (x)
  {
    digit = x % base_val;
    x /= base_val;
    if (digit < 10)
      x_str[n++] = digit + '0';
    else
      x_str[n++] = digit + 'A' - 10;  /* handle base > 9 */
  }

  /* Terminate string */
  x_str[n] = '\0';

  /* Reverse string */
  for (i=0; i<n/2; i++)
  {
    t = x_str[i];
    x_str[i] = x_str[n-i-1];
    x_str[n-i-1] = t;
  }
  printf ("\n%s\n", x_str);

  return 0;
}

The while loop will chop out the digits from the integer in a given base and feed the digits in reverse order in an array. The inner if - else handles base more than 9, and places uppercase alphabets when a digit value is greater than 10. The for loop reverses the string and gets the chopped number into string in forward order.

You need to adjust the size of x_str array as per your max capability. Define a macro for it. Note the above code is only for unsigned integers. For signed integers you need to first check if it is below 0, then add a ‘-‘ sign in x_str and then print the magnitude ie. apply the above code with -x . This can also be done by checking the sign bit, by masking, but will make the process dependent on storage of integer.

The base_val is the base in which you want to interpret the numbers.