After looking at all the possible ways, I believe my best route would be to go USB since serial ports are fading out on the new technologies and after looking at Microchip µCs with USB integrated it looks simple enough.
I've looked at the 18 series but I have some restrictions and using the Microchip Advance Part Selector, setting the following filters:
8-bit
USB connectivity
max 28 pins SOIC
2 x I²C
None of the resulting products have any non volatile memory so I will add an external EEPROM.
What I plan to do is to communicate with the PC via USB, design some software to manage up to 15 users and all the data will reside on the EEPROM for portability.
I am now looking at the 18F25J50
PIC to PC and vice versa communication via USB
PIC to EEPROM via I²C
RFID to PIC using an available I/O pin (Manchester code)
I selected to have a second I²C on the PIC for future use either in case I find a cheap RFID module that can communicate in this way or to interface multiple box via wireless.
The data stored is:
RFID tag = 14 Characters
Name =30 Char.
User ID = 15 Char.
User Password = 15 Char.
for 15 users I get a total of 1,110 bytes of data
My understanding is that an 24LC16B (16Kbit) will provide 16 x 1024 bits / 8 = 2KB of space.
If I am going the wrong way, please someone let me know...
Mike