Write BYTES to MIFARE without trancoding to ASCII-HEX

Projects Programming
9

Don't use a String: use a c-string! Try something like this (tested on PC; needs some porting to the arduino):

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>


const char    input_string[] = "11b701e0";
uint8_t       output_buffer[4];

size_t stringInterpreter  (const char* in, uint8_t* out);

int main (void)
{
    
    printf ("We are parsing: %s\n", input_string);
    
    stringInterpreter (input_string, output_buffer);    
    
    for (int i = 0; i < 4; ++i)
        printf ("Value #%i : %i\n", i, output_buffer[i]);
    
    return 0;
}

size_t stringInterpreter (const char* in, uint8_t* out)
{
    int i = 0;
    int j = 0;
    char hex_digits[3];
    
    for (i; in[i]; i += 2)
    {
        hex_digits[0] = in[i];
        hex_digits[1] = in[1+i];
        hex_digits[2] = '\0';
        
        out[j++] = (uint8_t) strtol (hex_digits, NULL, 16);
    }

    return j;
}

Output:

We are parsing: 11b701e0
Value #0 : 17
Value #1 : 183
Value #2 : 1
Value #3 : 224

EDIT: Will probably need some refining to get rid of magic numbers, etc.