static char * dec2binWzerofill(unsigned long Dec, unsigned int bitLength){
  static char bin[64]; 
  unsigned int i=0;

  while (Dec > 0) {
    bin[32+i++] = (Dec & 1 > 0) ? '1' : '0';
    Dec = Dec >> 1;
  }

  for (unsigned int j = 0; j< bitLength; j++) {
    if (j >= bitLength - i) {
      bin[j] = bin[ 31 + i - (j - (bitLength - i)) ];
    }else {
      bin[j] = '0';
    }
  }
  bin[bitLength] = '\0';
  
  return bin;
}