how convert large HEX string to binary array ?

how convert large HEX string to binary

I have a string with 14 characters . This is a hex represantation of 7bytes. I want to convert it to binary.

int32_t Hex2Bin( uint8_t * pHexString, uint8_t * pBinArray )
{
  int o = 0;
  int i = 0;

  while ( pHexString[ i ] != 0x00 )
  {
    switch ( pHexString[ i ] )
    {
      case '0':
        pBinArray[ o ] = 0x00;
        break;
      case '1':
        pBinArray[ o ] = 0x10;
        break;
      case '2':
        pBinArray[ o ] = 0x20;
        break;
      case '3':
        pBinArray[ o ] = 0x30;
        break;
      case '4':
        pBinArray[ o ] = 0x40;
        break;
      case '5':
        pBinArray[ o ] = 0x50;
        break;
      case '6':
        pBinArray[ o ] = 0x60;
        break;
      case '7':
        pBinArray[ o ] = 0x70;
        break;
      case '8':
        pBinArray[ o ] = 0x80;
        break;
      case '9':
        pBinArray[ o ] = 0x90;
        break;
      case 'A':
      case 'a':
        pBinArray[ o ] = 0xa0;
        break;
      case 'B':
      case 'b':
        pBinArray[ o ] = 0xb0;
        break;
      case 'C':
      case 'c':
        pBinArray[ o ] = 0xc0;
        break;
      case 'D':
      case 'd':
        pBinArray[ o ] = 0xd0;
        break;
      case 'E':
      case 'e':
        pBinArray[ o ] = 0xe0;
        break;
      case 'F':
      case 'f':
        pBinArray[ o ] = 0xf0;
        break;
      default:
        return -1;
    }

    if ( pHexString[ i + 1 ] == 0x00 )
      return -1;

    switch ( pHexString[ i + 1 ] )
    {
      case '0':
        pBinArray[ o ] |= 0x00;
        break;
      case '1':
        pBinArray[ o ] |= 0x01;
        break;
      case '2':
        pBinArray[ o ] |= 0x02;
        break;
      case '3':
        pBinArray[ o ] |= 0x03;
        break;
      case '4':
        pBinArray[ o ] |= 0x04;
        break;
      case '5':
        pBinArray[ o ] |= 0x05;
        break;
      case '6':
        pBinArray[ o ] |= 0x06;
        break;
      case '7':
        pBinArray[ o ] |= 0x07;
        break;
      case '8':
        pBinArray[ o ] |= 0x08;
        break;
      case '9':
        pBinArray[ o ] |= 0x09;
        break;
      case 'A':
      case 'a':
        pBinArray[ o ] |= 0x0a;
        break;
      case 'B':
      case 'b':
        pBinArray[ o ] |= 0x0b;
        break;
      case 'C':
      case 'c':
        pBinArray[ o ] |= 0x0c;
        break;
      case 'D':
      case 'd':
        pBinArray[ o ] |= 0x0d;
        break;
      case 'E':
      case 'e':
        pBinArray[ o ] |= 0x0e;
        break;
      case 'F':
      case 'f':
        pBinArray[ o ] |= 0x0f;
        break;
      default:
        return -1;
    }

    i += 2;
    o++;
  }

  return o;
}