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Sample code to read the unique MAC address from a Microchip MCP79411.

Ian Chilton <ian@ichilton.co.uk>

The MCP79411 is an I2C RTC chip which also includes 1K of EEPROM,
64 bytes of SRAM and a Unique ID.

There are 3 flavours of the MCP7941x, which differ in the Unique ID content:
MCP79410 - Blank
MCP79411 - EUI-48 Mac Address
MCP79412 - EUI-64 Mac Address

This code is for the MCP79411 so it reads 6 bytes starting from 0xF2

The chip uses an I2C address of 0x57 for the EEPROM and 0x6f for the RTC and SRAM
(the Wire library takes care of adding a LSB for read/write selection)

MAC addresses seem to start with 00:04:A3 which is correctly from their
allocation: http://hwaddress.com/?q=microchip