diff --git a/doorUtil.py b/doorUtil.py
index 663fef3..67d9b0f 100644
--- a/doorUtil.py
+++ b/doorUtil.py
@@ -1,21 +1,35 @@
 #!/usr/bin/env python3
+import bitstring
+
 import requests
 import csv
 from io import StringIO
 
 from common import *
 
-def hexToCode(hex):
-    b = bin(int(hex, 16))[2:]
-    facility = int(b[0:8], 2)
-    code = int(b[9:24], 2)
-    return((facility, code))
+# Reference for H10301 card format:
+# https://www.hidglobal.com/sites/default/files/hid-understanding_card_data_formats-wp-en.pdf
+
+
+def hexToCode(h):
+    b = bitstring.Bits(hex=h)
+    facility = b[7:15].uint
+    code = b[15:31].uint
+    return ((facility, code))
+
 
 def codeToHex(facility, code):
-    return "{:08X}".format(int(bin(facility)[2:] + "0" + bin(code)[2:] + "1", 2))
+    b = bitstring.pack('0b000000, uint:1, uint:8, uint:16, uint:1', 0,
+                       facility, code, 0)
+    # calculate parity bits
+    b[6] = b[7:19].count(1) % 2  # even parity
+    b[31] = not (b[19:31].count(1) % 2)  # odd parity
+    return b.hex.upper()
+
 
 # hexToCode("01E29DA1") <-> codeToHex(241, 20176)
 
+
 def forEachDoor(fxn):
     for door in doors.values():
         print(door.name)