I took the deposit which had been written by Cyril M and updated by adding function as writing on the cards. developed version 18 I purposely let the raw code with test phases in comments. Do not hesitate to uncomment to see the return value. There is also a procedure ( autoread) that I think to finish shortly to read the cards without human intervention. you can enable it for testing. Now if someone wants to complete the work, free to you.
For readings and writings of cards it will write the procedures to illuminate the code, everyone has their method, here is a tutorial, so very simple and very imperfect.
It remains to describe some functions (read write a numeric value, the Increment, Decrement) Scard the beginning and end transaction function also seems very important, I would complete later ...