Interfacing multiple external EEPROM with Arduino through I2C

EEPROM is a very fundamental feature of Arduino and it has internal EEPROM for this purpose. But sometimes, we need some more to use. In that situation, some dedicated EEPROM ICs like 24Cxxx ICs. In this article, we are going to interface external EEPROM with Arduino. So let’s start!

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EEPROM ICs:

There are different types of EEPROM ICs in the market from a range of memory capacities. Most of these ICs use the I²C protocol for communication.

Here, SCL & SDA are for I2C communication, A0, A1, A2 are for address. WP is Write Protection, if it is connected to VDD, EEPROM is is write-protected, and if it is connected to GND, no Write Protection.

Circuit diagram:

Here is the circuit diagram with 3 external EEPROMs with Arduino.

This article can be useful too: How to remove noise/garbage from the HD44780 LCD display

U1, U2, U3 are EEPROM ICs. If you need more memory, then you can add ICs up to 8 in total. The base address for EEPROM is 0x50. With this base address, you need to add the EEPROM IC address.

A2	A1	A0	Address (Decimal, HEX)	EEPROM ADDRESS
0	0	0	0 , 0x00	0x50
0	0	1	1 , 0x01	0x51
0	1	0	2 , 0x02	0x52
0	1	1	3 , 0x03	0x53
1	0	0	4 , 0x04	0x54
1	0	1	5 , 0x05	0x55
1	1	0	6 , 0x06	0x56
1	1	1	7 , 0x07	0x57

You can use this hex calculator here.

Arduino Code:

//eeprom
#include <Wire.h>
#define eeprom1 0x50 //for eeprom1
#define eeprom2 0x51 //for eeprom2
#define eeprom3 0x52 //for eeprom2
//basic address for eeprom is 0x50. 
//You need to add the eeprom ic address (A0,A1,A2) with this value
unsigned int address = 0;//start address

void setup()
{
  Serial.begin(9600); 
  Wire.begin(); 
  Serial.println("Writing at eeprom1: 66666");
  for (address = 0; address < 5; address++)
  {
    writeEEPROM(eeprom1, address, 6); 
  }
  Serial.println("EEPROM1 read:");
  for (address = 0; address < 5; address++)
  {
    Serial.print(readEEPROM(eeprom1, address));
  }
  Serial.println();
  Serial.println("Writing at eeprom2: 44444");
  for (address = 0; address < 5; address++)
  {
    writeEEPROM(eeprom2, address, 4);
  }
  Serial.println("EEPROM2 read:");
  for (address = 0; address < 5; address++)
  {
    Serial.print(readEEPROM(eeprom2, address));
  }

}

void loop()
{
 //other codes here

}

//defines the writeEEPROM function
void writeEEPROM(int dev_address, unsigned int eeaddress, byte data )
{
  Wire.beginTransmission(dev_address);
  Wire.write((int)(eeaddress >> 8)); //writes the MSB
  Wire.write((int)(eeaddress & 0xFF)); //writes the LSB
  Wire.write(data);
  Wire.endTransmission();
  delay(5);//this is important to save data
}

//defines the readEEPROM function
byte readEEPROM(int dev_address, unsigned int eeaddress )
{
  byte readdata = 0xFF;
  Wire.beginTransmission(dev_address);
  Wire.write((int)(eeaddress >> 8)); //writes the MSB
  Wire.write((int)(eeaddress & 0xFF)); //writes the LSB
  Wire.endTransmission();
  Wire.requestFrom(dev_address, 1);
  if (Wire.available())
    readdata = Wire.read();
    delay(5);
  return readdata;
}

Output:

As you see, we saved data to two different EEPROMs, and then we read from those.

Conclusion:

This way, we can add external EEPROM ICs to cover our memory requirements. I hope this will help you a lot in EEPROM interfacing. Thanks for reading, don’t forget to subscribe.

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