Chapter 19. EEPROM

In Chapter 16 we used external EEPROM (electrically erasable and programmable ROM) for nonvolatile external data storage. For making a data logger it was just right: EEPROM provides low-power, long-term storage of fairly large amounts of data. But if all you want is a little bit of data to survive a chip reset, adding an extra chip and tying up the SPI or I2C lines just for a few bytes of configuration data seems overkill. That’s why the Atmel chip designers put a small amount of EEPROM on each of the ATmega chips for you to use.

In this chapter, we’ll turn the AVR into a Vigenère Cipher encoder and decoder, storing the encryption key strings in nonvolatile EEPROM memory so that you don’t have to remember ...

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