Question

I am using an rs232 HID reader.
Its manual says that its output is

  CCDDDDDDDDDDXX     
where CC is reserved for HID    
      DDDDDDDDDD is the transponder (the card) data
      XX is a checksum    

the checksum is well explained and irrelevant here. About DDDDDDDDDD only says valid values are 0000000000 to 1FFFFFFFFF but no indication of how it converts to what is printed on front face of the card.
I have 3 sample cards, sadly on a short range (edit plus an extra one). here I show them:

readed from rs232     shown on card    
 00000602031C27          00398    
 00000602031F2A          00399    
 0000060203202B          00400    
 00000601B535F1          55962       **new 

Also I have a DB with 1000 cards loaded (what is printed on front) so I need the the decode path from what I read on rs232 to what is printed on front.

Some values from DB (I have seen the cards, but I have no phisical access to them now)

55503
60237
00833

Thanks a lot to every one.

Answer 1

Googling for the string “CCDDDDDDDDDDXX” returns http://www.rfideas.com/downloads/SerialAppNote8.pdf which seems to describe how to decode the numbers. I don’t guarantee if that is accurate.

Decoding the Standard 26-bit Format

Message sent by the reader:

C C D D D D D D D D D D X X
---------------------------
0 0 0 0 0 6 0 2 0 3 1 C 2 7
0 0 0 0 0 6 0 2 0 3 1 F 2 A
0 0 0 0 0 6 0 2 0 3 2 0 2 B
0 0 0 0 0 6 0 1 B 5 3 5 F 1

Stripping off the checksum, X, and reducing the data to binary gives:

  C    C    D    D    D    D    D    D    D    D    D    D
cccc cccc zzzz zzzz zzzz zspf ffff fffn nnnn nnnn nnnn nnnp
-----------------------------------------------------------
0000 0000 0000 0000 0000 0110 0000 0010 0000 0011 0001 1100
0000 0000 0000 0000 0000 0110 0000 0010 0000 0011 0001 1111
0000 0000 0000 0000 0000 0110 0000 0010 0000 0011 0010 0000
0000 0000 0000 0000 0000 0110 0000 0001 1011 0101 0011 0101

All the Card Data Characters to the left of the 7th can be ignored.

• c = HID Specific Code.
• z = leading zeros
• s = start sentinel (it is always a 1)
• p = parity odd and even (12 bits each).
• f = Facility Code 8 bits
• n = Card Number 16 bits

From this we can see that

• 00000602031C27 → n = 0b0000000110001110 = 398
• 00000602031F2A → n = 0b0000000110001111 = 399
• 0000060203202B → n = 0b0000000110010000 = 400
• 00000601B535F1 → n = 0b1101101010011010 = 55962

So, for your example, we may probably get:

• 55503
• (f, n) = 0b0000_0001__1101_1000_1100_1111
• odd parity of first 12 bits = 0
• even parity of last 12 bits = 0
• result = 00000403b19e56