I have found several items on the internet to read in the HEX code, but what about the numeric code on the tag?
For instance, I have one tag that has the HEX result of 0D0031EF53
the number on the tag is 0003272531
is it a one-way hash? if so, how to I convert the number to the HEX value?
thanks in advance.
The number 0003272531 on the tag is in decimal.
That is 31EF53 in hexadecimal.
To convert the number manually go to this website.
Were you considering using an Arduino to do this?
The '0D' could be anything - vendor specific code, supplier code - who knows!
To convert a hex value like that use the 'standard' C++ functions - convert the hex string to a long integer and then (if you want to) convert that to a string.
Hex to Dec (prefix the hex with '0x')
Long Int to String (non-standard but probably works in Arduinoland)
Above methods are just suggestions - there are doubtless other ways that others may suggest too.
It would be useful to know what you want to do with all this - it may affect responses you get.
If you are thinking about getting an RFID reader for your Arduino (a Mifare MIRC522, for example) you might like to watch my YouTube video #34 RFID Reader/Writer (Mifare MFRC522) with a Logic Level Shifter that will be published at noon on Friday 13th May 2016.
Please provide your code (using code tags). Also please provide links to the reader that you use and the library that you use. Lastly provide a sample of the number on the tag (complete) and the matching data that you get when you read the tag.
Ralph_S_Bacon:
The '0D' could be anything - vendor specific code, supplier code - who knows!
Carriage return?
Ralph_S_Bacon:
If you are thinking about getting an RFID reader for your Arduino (a Mifare MIRC522, for example) you might like to watch my YouTube video #34 RFID Reader/Writer (Mifare MFRC522) with a Logic Level Shifter that will be published at noon on Friday 13th May 2016.
Better repair that link then!
Paul__B:
Better repair that link then!
Doh! That link won't become active till noon GMT on Friday. Should have thought of that! Oh well...
Some vendors of access control equipment do scramble the code in their readers so the number that comes out is not the same as the token. This is part a security thing but mainly to stop people using third party cheaper readers when enlarging their system.
Ralph_S_Bacon:
Doh! That link won't become active till noon GMT on Friday. Should have thought of that! Oh well...
Well, it is now past noon GMT and it is Friday the 13th, so I seriously suggest you repair the broken link you posted!
Paul__B:
Well, it is now past noon GMT and it is Friday the 13th, so I seriously suggest you repair the broken link you posted!
Even though I am now in a different country to where I live I have now logged in and repaired that broken link. Note to self: don't trust YouTube to generate working links when you are not there to check them!
Seriously though, thanks for bringing this to my attention, I have no idea how it became a broken link considering it was pasted from YouTube (unless it was a private, pre-published link just for my use). 
The breakage was due to a glitch pasting it into the dialog generated by the link ("chain") icon when the default "http://" root is not highlighted.
Read reply #8.
Also some card numbers have no relationship between the number printed on them and the number the card holds. Again this is for security. The card number is simply a reference to the look up table of valid cards.
Think about it, if there was a relationship, you could simply write down the number of someone else's card and then go home an clone the card.