Tutorial

Using Arduino with an I2C EEPROM

I got my hands on an AT24C256 (256 kbit = 32 kbyte serial EEPROM). I found no library for it, so I

created a small sketch with few functions to show how the i2c_eeprom_write_page and

i2c_eeprom_read_byte functions work.

Because this chip is I2C, it only uses the analog pins 4 & 5 (SDA and SCL), and of course the power

(5V) and GND.

Connect as follows:

Arduino pin 4 to EEPROM pin 5

Arduino pin 5 to EEPROM pin 6

Arduino 5V to EEPROM pin 8

Arduino GND to EEPROM pin 1,2,3,4

Be sure to leave pin 7 of the EEPROM open or tie it to GND otherwise the EEPROM will be write

protected.

Just a few quick functions for reading/writing the EEPROM (not a library, yet). 'deviceaddress' refers to

the EEPROM I2C address, eg. 0x50.

* Use the I2C bus with EEPROM 24LC64

* Sketch: eeprom.pde

* Author: hkhijhe

* Date: 01/10/2010

#include <Wire.h> //I2C library

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Using Arduino with an I2C EEPROM I got my hands on an AT24C256 (256 kbit = 32 kbyte serial EEPROM). I found no library for it, so I created a small sketch with few functions to show how the i2c_eeprom_write_page and i2c_eeprom_read_byte functions work. Because this chip is I2C, it only uses the analog pins 4 & 5 (SDA and SCL), and of course the power (5V) and GND.
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void i2c_eeprom_write_byte( int deviceaddress, unsigned int eeaddress, byte data ) { int rdata = data; Wire.beginTransmission(deviceaddress); Wire.send((int)(eeaddress >> 8)); // MSB Wire.send((int)(eeaddress & 0xFF)); // LSB Wire.send(rdata); Wire.
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// maybe let's not read more than 30 or 32 bytes at a time! void i2c_eeprom_read_buffer( int deviceaddress, unsigned int eeaddress, byte *buffer, int length ) { Wire.beginTransmission(deviceaddress); Wire.send((int)(eeaddress >> 8)); // MSB Wire.send((int)(eeaddress & 0xFF)); // LSB Wire.endTransmission(); Wire.requestFrom(deviceaddress,length); int c = 0; for ( c = 0; c < length; c++ ) if (Wire.available()) buffer[c] = Wire.
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Serial.print((char)b); //print content to serial port addr++; //increase address b = i2c_eeprom_read_byte(0x50, addr); //access an address from the memory } Serial.