My basic question is: What is a good alternative to EEPROM chips for external memory on the Arduino Unor R3?

I know that there are EEPROM chips when one would like an external memory chip. It, in fact, seems like this is the standard choice. I am wondering if there are any other good ways to work with external memory. Are there, for example, memory chips that work a bis simpler? Like, a chip that doesn't require any specific libraries in the Arduino?

(I do not have extensive experience working with the Arduino.)

  • What is the problem with using a library? If you have some external memory, you have to communicate with this memory somehow. This already makes it "not simple". Note that you are not required to use a library. You could just write your own code that does the communication. But that would make it even less simple
    – Gerben
    May 12, 2016 at 17:21
  • @Gerben: No problem at all. I was just wondering.
    – John Doe
    May 12, 2016 at 17:34

3 Answers 3


There is no DRAM, SRAM nor flash interface in ATmega, so you can't extend your chip memory. You can only connect serial (SPI, I2C) or parallel memory (usind GPIO).

Neither SPI nor I2C require any specific libraries. SPI is much simpler to program than I2C and much faster, but require more wires.

Instead of using rather slow EEPROM, you can try FRAM (non-volatile) or SRAM (volatile, but may be battery-sustained). They are usually available with the same interface as EEPROM, but don't suffer from limited number of erase cycles. FRAM can withstand ridiculous number of erasures, SRAM is virtually indestructible.

  • In what way is SPI easier to program than I2C?
    – Liftyee
    Aug 6, 2022 at 23:50

No. There is no external memory interface on the ATmega328P, so all external memory requires some sort of library to use.


Personally I like the Amtel 24C256 chip/module. It is I2C enabled and the standard Wire library is all you need to talk to it. It is 256 bits or 32K 8 bit bytes in size. Data is sent and read in byte chunks. Addressing is at the bit level. It can run on 3.3V and 5V. Ebay has a bunch of suppliers for it. There's a number of good How-To's on line.

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