Convert two ASCII Hexadecimal Characters (Two ASCII bytes) in one byte

Question

I want to convert two ASCII bytes to one hexadecimal byte. eg.

0x30 0x43 => 0x0C , 0x34 0x46 => 0x4F ...

The ASCII bytes are a number bet

Answer 1

You can use strtol(), which is part of avr-libc, or you can write just your specific case pretty easily:

unsigned char charToHexDigit(char c)
{
  if (c >= 'A')
    return c - 'A' + 10;
  else
    return c - '0';
}

unsigned char stringToByte(char c[2])
{
  return charToHexDigit(c[0]) * 16 + charToHexDigit(c[1]);
}