{"id":22061,"date":"2018-01-14T21:33:45","date_gmt":"2018-01-14T14:33:45","guid":{"rendered":"http:\/\/tom.ji42.com\/?p=22061"},"modified":"2023-08-15T07:35:59","modified_gmt":"2023-08-15T00:35:59","slug":"using-arduino-with-an-i2c-eeprom","status":"publish","type":"post","link":"https:\/\/tom.tomwork.net\/?p=22061","title":{"rendered":"Using Arduino with an I2C EEPROM"},"content":{"rendered":"

I got my hands on an\u00a0AT24C256<\/span>\u00a0(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.<\/p>\n

Because this chip is\u00a0I2C<\/span>, it only uses the analog pins 4 & 5 (SDA and SCL), and of course the power (5V) and GND.<\/p>\n

Connect as follows:<\/p>\n

Arduino analog pin 4 to EEPROM pin 5
\nArduino analog pin 5 to EEPROM pin 6
\nArduino 5V to EEPROM pin 8
\nArduino GND to EEPROM pin 1,2,3,4<\/p>\n

<\/p>\n

Be sure to leave pin 7 of the EEPROM open or tie it to GND otherwise the EEPROM will be write protected.<\/p>\n

Just a few quick functions for reading\/writing the EEPROM (not a library, yet). ‘deviceaddress’ refers to the EEPROM\u00a0I2C\u00a0address, eg. 0x50.<\/p>\n\n\n\n
\/*
\n* Use the I2C bus with EEPROM 24LC64
\n* Sketch: eeprom.ino
\n*
\n* Author: hkhijhe
\n* Date: 01\/10\/2010
\n*
\n*
\n*\/#include <Wire.h><\/p>\n

void i2c_eeprom_write_byte( int deviceaddress, unsigned int eeaddress, byte data ) {
\nint rdata = data;
\nWire.beginTransmission(deviceaddress);
\nWire.write((int)(eeaddress >> 8)); \/\/ MSB
\nWire.write((int)(eeaddress & 0xFF)); \/\/ LSB
\nWire.write(rdata);
\nWire.endTransmission();
\n}<\/p>\n

\/\/ WARNING: address is a page address, 6-bit end will wrap around
\n\/\/ also, data can be maximum of about 30 bytes, because the Wire library has a buffer of 32 bytes
\nvoid i2c_eeprom_write_page( int deviceaddress, unsigned int eeaddresspage, byte* data, byte length ) {
\nWire.beginTransmission(deviceaddress);
\nWire.write((int)(eeaddresspage >> 8)); \/\/ MSB
\nWire.write((int)(eeaddresspage & 0xFF)); \/\/ LSB
\nbyte c;
\nfor ( c = 0; c < length; c++)
\nWire.write(data[c]);
\nWire.endTransmission();
\n}<\/p>\n

byte i2c_eeprom_read_byte( int deviceaddress, unsigned int eeaddress ) {
\nbyte rdata = 0xFF;
\nWire.beginTransmission(deviceaddress);
\nWire.write((int)(eeaddress >> 8)); \/\/ MSB
\nWire.write((int)(eeaddress & 0xFF)); \/\/ LSB
\nWire.endTransmission();
\nWire.requestFrom(deviceaddress,1);
\nif (Wire.available()) rdata = Wire.read();
\nreturn rdata;
\n}<\/p>\n

\/\/ maybe let’s not read more than 30 or 32 bytes at a time!
\nvoid i2c_eeprom_read_buffer( int deviceaddress, unsigned int eeaddress, byte *buffer, int length ) {
\nWire.beginTransmission(deviceaddress);
\nWire.write((int)(eeaddress >> 8)); \/\/ MSB
\nWire.write((int)(eeaddress & 0xFF)); \/\/ LSB
\nWire.endTransmission();
\nWire.requestFrom(deviceaddress,length);
\nint c = 0;
\nfor ( c = 0; c < length; c++ )
\nif (Wire.available()) buffer[c] = Wire.read();
\n}<\/p>\n

void setup()
\n{
\nchar somedata[] = “this is data from the eeprom”; \/\/ data to write
\nWire.begin(); \/\/ initialise the connection
\nSerial.begin(9600);
\ni2c_eeprom_write_page(0x50, 0, (byte *)somedata, sizeof(somedata)); \/\/ write to EEPROM<\/p>\n

delay(100); \/\/add a small delay<\/p>\n

Serial.println(“Memory written”);
\n}<\/p>\n

void loop()
\n{
\nint addr=0; \/\/first address
\nbyte b = i2c_eeprom_read_byte(0x50, 0); \/\/ access the first address from the memory<\/p>\n

while (b!=0)
\n{
\nSerial.print((char)b); \/\/print content to serial port
\naddr++; \/\/increase address
\nb = i2c_eeprom_read_byte(0x50, addr); \/\/access an address from the memory
\n}
\nSerial.println(” “);
\ndelay(2000);
\n}<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":"

I got my hands on an\u00a0AT24C256\u00a0(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\u00a0I2C, it only uses the analog pins 4 & 5 (SDA and SCL), and of course […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[13],"tags":[],"class_list":["post-22061","post","type-post","status-publish","format-standard","hentry","category-13"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p6cOVM-5JP","_links":{"self":[{"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/posts\/22061","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=22061"}],"version-history":[{"count":4,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/posts\/22061\/revisions"}],"predecessor-version":[{"id":26504,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=\/wp\/v2\/posts\/22061\/revisions\/26504"}],"wp:attachment":[{"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=22061"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=22061"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tom.tomwork.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=22061"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}