Quote Originally Posted by andybarrett1 View Post

Not quite sure how the number on the card relates to the hex number embeded in the card...
There is no relation except for the CRC. My understanding is that you have to swipe the cards and capture the embedded numbers (Tag) which you can then use in your code. The output from the RFID is TTL level and using a MAX232 is one way forward.

I have read some posts that suggest the CRC is used to catch bad data but the datasheet says the CRC is calculated using the card number. Examples I have seen ignore the CRC and end byte. I guess the cards are reasonably reliable and do not need CRC checking or end byte detection, who knows?