Check out the Adafruit site, there's some tutorials and libraries there too
There are various suppliers of NFC modules on ebay, most supply documentation and libraries etc. Here's one that looks interesting: **broken link removed**
The whole point of authentication and encryption is to keep data and systems secure that use NFC, so I won't be helping you to perform a hack. Most new cards as far as I know will allow full access to the data blocks using Key A. However, to answer your question, yes the MiFare chipsets have been compromised by some less scrupulous types, so it is possible
I assume that you are sending ascii text. Compare the incoming data value to the ascii table values. Number characters have values from 48 to 57.
If you are sending raw number values (integers, floats etc.) mixed with ascii text. Then you need to define a simple protocol that sends well defined datapackets.
"Using Arduino" means that you are probably coding in C.
It is very difficult to give more advice without knowing the details of the serial data. Can you give an example of incoming data and what you need to do with it.
I still don't understand what exactly is the problem. You do not know how to send data, or you do not know how to convert numbers to strings, or you do not know how to split the string in 2 character groups.. what is it?
After we execute the code...we have to give "Get0100300" as input in serial monitor and press enter... it should print in serial monitor as
Ge
t0
10
03
00
It is impossible to help you when you give out small pieces of information here and there. Why don't you describe the whole system and also tell us what you have done so far. Post all the code working code you have so far. And detailed info what you are trying to accomplish.