Veja também o vídeo sobre o AT24C256.
Veja também o vídeo que mostra a classe feita para facilitar a gravação e leitura da memória:
Código-fonte:
/*
Baseado nos exemplos abaixo:
http://hobbytronics.co.uk/eeprom-page-write
http://playground.arduino.cc/Code/EEPROMWriteAnything
Fabiano A. Arndt
www.youtube.com/fabianoallex
www.facebook.com/dicasarduino
*/
#include <Wire.h>
/*************************************************************************************************************
*******************************CLASSE EE24CXXX - CI I2C EEPROM AT24C128/256***********************************
**************************************************************************************************************/
class EE24CXXX {
private:
byte _device_address;
public:
EE24CXXX(byte device_address){ _device_address = device_address; }
void write(unsigned int eeaddress, unsigned char * data, unsigned int data_len);
void read (unsigned int eeaddress, unsigned char * data, unsigned int data_len);
template <class T> int write(unsigned int eeaddress, const T& value);
template <class T> int read(unsigned int eeaddress, T& value);
};
void EE24CXXX::write(unsigned int eeaddress, unsigned char * data, unsigned int data_len) {
unsigned int address;
unsigned int page_space;
unsigned int page=0;
unsigned int num_writes;
unsigned char first_write_size;
unsigned char last_write_size;
unsigned char write_size;
page_space = int(((eeaddress/64) + 1)*64)-eeaddress; // Calculate space available in first page
if (page_space>16) { // Calculate first write size
first_write_size = page_space-((page_space/16)*16);
if (first_write_size==0) { first_write_size=16; }
} else {
first_write_size = page_space;
}
if (data_len>first_write_size) { last_write_size = (data_len-first_write_size)%16; } // calculate size of last write
num_writes = (data_len>first_write_size) ? ((data_len-first_write_size)/16)+2 : 1; // Calculate how many writes we need
unsigned char i=0, counter=0;
address = eeaddress;
for (page=0; page<num_writes; page++) {
if (page == 0) {
write_size = first_write_size;
} else if(page == (num_writes-1)) {
write_size = last_write_size;
} else {
write_size = 16;
}
Wire.beginTransmission(_device_address);
Wire.write((int)((address) >> 8)); // MSB
Wire.write((int)((address) & 0xFF)); // LSB
counter = 0;
do {
Wire.write((byte) data[i++]);
counter++;
} while(counter<write_size);
Wire.endTransmission();
address += write_size; // Increment address for next write
delay(5); // needs 5ms for page write
}
}
void EE24CXXX::read(unsigned int eeaddress, unsigned char * data, unsigned int data_len){
unsigned char i = 0;
unsigned int size = data_len;
unsigned int j=0;
while (size > 0){
Wire.beginTransmission(_device_address);
eeaddress += j*28;
Wire.write((int)(eeaddress >> 8)); // MSB
Wire.write((int)(eeaddress & 0xFF)); // LSB
Wire.endTransmission();
if (size >= 28) {
Wire.requestFrom(_device_address, (unsigned int) 28);
size -= 28;
} else {
Wire.requestFrom(_device_address, (unsigned int) size);
size = 0;
}
while(Wire.available()) { data[i++] = Wire.read(); }
j++;
}
}
template <class T> int EE24CXXX::write(unsigned int eeaddress, const T& value) {
const byte* p = (const byte*)(const void*)&value;
unsigned char data[sizeof(value)+1];
for (int i=0; i<sizeof(value); i++) { data[i] = *p++; }
data[sizeof(value)] = '\n';
write(eeaddress, data, sizeof(value));
return sizeof(value);
}
template <class T> int EE24CXXX::read(unsigned int eeaddress, T& value) {
byte * p = (byte*)(void*)&value;
unsigned char c[sizeof(value)];
read(eeaddress, c, sizeof(value));
for (int i=0; i<sizeof(value); i++) { *p++ = c[i]; }
return sizeof(value);
}
/*************************************************************************************************************
*******************************FIM - CLASSE EE24CXXX - CI I2C EEPROM AT24C128/256*****************************
**************************************************************************************************************/
EE24CXXX m(0x50);
struct teste{
int a;
int b;
int c;
};
void setup() {
Serial.begin(9600);
Wire.begin();
char i[] = {"1234567890"};
char j[10];
m.write(18522, i); //grava na memória a quantidade de bytes ocupada pelo tipo de dados passado
int count = m.read(18522, j); //carrega da memória a quantidade de bytes
Serial.print("Quant: ");
Serial.println(count);
Serial.print("Valor: ");
Serial.println(j);
}
void loop() { }
