Program 2

// Written by Nick Gammon
// February 2011

// Note: maximum address is 0x7FFF (32 Kbytes)

#include <Wire.h>

const byte rom = 0x50;    // Address of 24LC256 eeprom chip

    unsigned char somedata[][16] = {
{0xAA, 0x55, 0xAA, 0x55, 0xAA, 0x55, 0x38, 0x36, 0x36, 0x2E, 0x32, 0x37, 0x38, 0x36, 0x36, 0x2E},
{0x32, 0x37, 0x03, 0x93, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x7F, 0x4A, 0x02, 0x00, 0xFA, 0xC5},
{0xFA, 0xFB, 0xF8, 0xF9, 0xFE, 0xFF, 0xF2, 0xF3, 0xF7, 0xDF, 0xFA, 0x57, 0x03, 0x93, 0x00, 0x00},
{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xD0, 0x00, 0x03, 0x93},
{0x02, 0x00, 0x28, 0x00, 0x0E, 0x99, 0x00, 0x00, 0x00, 0x00, 0x00, 0x15, 0xC4, 0xC4, 0x50, 0x00},
{0x4C, 0x00, 0x00, 0x60, 0x58, 0x4D, 0x00, 0x00, 0x00, 0x2E, 0x09, 0x44, 0x00, 0x00, 0xC6, 0x47},
{0x00, 0x00, 0x55, 0x22, 0x00, 0x60, 0xA1, 0x60, 0x00, 0xC4, 0xC4, 0x50, 0x00, 0x4C, 0x00, 0x00},
{0x00, 0x58, 0x4D, 0x00, 0x00, 0x00, 0x2E, 0x09, 0x44, 0x00, 0x00, 0xE3, 0xA3, 0x00, 0x00, 0x55},
{0x22, 0x00, 0x60, 0xA1, 0x26, 0x00, 0x02, 0x00, 0xF7, 0xDF, 0xFA, 0x60, 0xAA, 0xFF, 0xE1, 0x1E},
{0x4C, 0x08, 0x08, 0x00, 0x04, 0x28, 0x02, 0xF1, 0x0A, 0x00, 0xA6, 0x7F, 0x0A, 0x08, 0x02, 0x02},
{0x00, 0x00, 0x28, 0xFF, 0x71, 0xAC, 0x85, 0x89, 0x6F, 0x17, 0x08, 0x08, 0x08, 0x00, 0x00, 0x28},
{0xFF, 0x2B, 0x00, 0x1C, 0xAA, 0x7D, 0x08, 0x08, 0x02, 0x02, 0x00, 0x00, 0x28, 0x17, 0x00, 0x93},
{0x02, 0xB8, 0xB7, 0x22, 0x4C, 0x80, 0x80, 0x00, 0x04, 0x28, 0x7B, 0x00, 0x00, 0x00, 0x82, 0x92},
{0x2E, 0x44, 0x01, 0x01, 0x00, 0x04, 0x28, 0x01, 0x74, 0x00, 0x82, 0x00, 0x99, 0x0B, 0x08, 0x10},
{0x10, 0x00, 0x00, 0x28, 0x03, 0x5F, 0x61, 0x57, 0x9E, 0x6B, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00},
{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
};

void setup (void)
  {
  Serial.begin (9600);   // debugging

  Wire.begin ();

  // test: write the number 123 to address 0x1234
  /*writeEEPROM (rom, 0, 123);

  // read back to confirm
  byte a = readEEPROM (rom, 0);

  Serial.println (a, DEC);  // display to confirm

  // test: write a string to address 0x1000
  byte hello [] = "Hello, world!";

  writeEEPROM (rom, 10, hello, sizeof hello);*/
  byte test;


  for(byte i = 0; i < 16; i++)
  {
    writeEEPROM (rom, i, somedata[i], sizeof somedata[i]);
  }

  for(short i = 0; i < 256; i++)
  {
    if(i % 16 == 0) Serial.println(" ");
    byte err = readEEPROM(rom, i);
    Serial.print ("0x");
    Serial.print (err, HEX);
    Serial.print ( ", ");
  }
}  // end of setup

void loop() {}  // no main loop


// write len (max 32) bytes to device, returns non-zero on error
//  return code: 0xFF means buffer too long
//             other: other error (eg. device not present)

// Note that if writing multiple bytes the address plus
//  length must not cross a 64-byte boundary or it will "wrap"

byte writeEEPROM (byte device, unsigned int addr, byte * data, byte len )
  {
  byte err;
  byte counter;

  if (len > BUFFER_LENGTH)  // 32 (in Wire.h)
    return 0xFF;  // too long

  Wire.beginTransmission(device);
  Wire.write ((byte) (addr >> 8));    // high order byte
  Wire.write ((byte) (addr & 0xFF));  // low-order byte
  Wire.write (data, len);
  err = Wire.endTransmission ();

  if (err != 0)
    return err;  // cannot write to device

  // wait for write to finish by sending address again
  //  ... give up after 100 attempts (1/10 of a second)
  for (counter = 0; counter < 100; counter++)
    {
    delayMicroseconds (300);  // give it a moment
    Wire.beginTransmission (device);
    Wire.write ((byte) (addr >> 8));    // high order byte
    Wire.write ((byte) (addr & 0xFF));  // low-order byte
    err = Wire.endTransmission ();
    if (err == 0)
      break;
    }

  return err;

  } // end of writeEEPROM

// write one byte to device, returns non-zero on error
byte writeEEPROM (byte device, unsigned int addr, byte data )
  {
  return writeEEPROM (device, addr, &data, 1);
  } // end of writeEEPROM

// read len (max 32) bytes from device, returns non-zero on error
//  return code: 0xFF means buffer too long
//               0xFE means device did not return all requested bytes
//             other: other error (eg. device not present)

// Note that if reading multiple bytes the address plus
//  length must not cross a 64-byte boundary or it will "wrap"

byte readEEPROM (byte device, unsigned int addr, byte * data, byte len )
  {
  byte err;
  byte counter;

  if (len > BUFFER_LENGTH)  // 32 (in Wire.h)
    return 0xFF;  // too long

  Wire.beginTransmission (device);
  Wire.write ((byte) (addr >> 8));    // high order byte
  Wire.write ((byte) (addr & 0xFF));  // low-order byte
  err = Wire.endTransmission ();

  if (err != 0)
    return err;  // cannot read from device

  // initiate blocking read into internal buffer
  Wire.requestFrom (device, len);

  // pull data out of Wire buffer into our buffer
  for (counter = 0; counter < len; counter++)
    {
    data [counter] = Wire.read ();
    }

  return 0;  // OK
  }  // end of readEEPROM

// read one byte from device, returns 0xFF on error
byte readEEPROM (byte device, unsigned int addr )
  {
  byte temp;

  if (readEEPROM (device, addr, &temp, 1) == 0)
    return temp;

  return 0xFF;

  }  // end of readEEPROM