Convert Hexadecimal to Decimal in AVR Studio?

Question

How can I convert a hexadecimal (unsigned char type) to decimal (int type) in AVR Studio?

Are there any built-in functions available for these?

Answer 1

On AVRs, I had problems using the traditional hex 2 int approach:

char *z="82000001";
uint32_t x=0;
sscanf(z, "%8X", &x);

or

x = strtol(z, 0, 16);

They simply provided the wrong output, and didn't have time to investigate why.

So, for AVR Microcontrollers I wrote the following function, including relevant comments to make it easy to understand:

/**
 * hex2int
 * take a hex string and convert it to a 32bit number (max 8 hex digits)
 */
uint32_t hex2int(char *hex) {
    uint32_t val = 0;
    while (*hex) {
        // get current character then increment
        char byte = *hex++; 
        // transform hex character to the 4bit equivalent number, using the ascii table indexes
        if (byte >= '0' && byte <= '9') byte = byte - '0';
        else if (byte >= 'a' && byte <='f') byte = byte - 'a' + 10;
        else if (byte >= 'A' && byte <='F') byte = byte - 'A' + 10;    
        // shift 4 to make space for new digit, and add the 4 bits of the new digit 
        val = (val << 4) | (byte & 0xF);
    }
    return val;
}

Example:

char *z ="82ABC1EF";
uint32_t x = hex2int(z);
printf("Number is [%X]\n", x);

Will output:

EDIT: sscanf will also work on AVRs, but for big hex numbers you'll need to use "%lX", like this:

char *z="82000001";
uint32_t x=0;
sscanf(z, "%lX", &x);