EEPROM Arduino

arduino_eeprom.c

#include <Wire.h> // specify use of Wire.h library.

#define FLOAT_LENGTH 4
#define DOUBLE_LENGTH 8
#define UINT_LENGTH 2

const int EEPROM_DEVICE_ADDR = 0x50;
int loops = 0;

void setup() 
{
  Wire.begin(); // join i2c bus (address optional for master) 
  Serial.begin(9600);  // setup serial for output 

  float foo = 0.654321;
  int ret1 = EEPROM_writeFloat(0x590, foo);
  Serial.print("First write: ");
  Serial.print(ret1);
  Serial.print("\n");

  // writes take a few ms and are non-blocking
  delay(10);

  float bar = 0.123456;
  int ret2 = EEPROM_writeFloat(0x5b0, bar);
  Serial.print("Second write: ");
  Serial.print(ret2);
  Serial.print("\n");

  // writes take a few ms and are non-blocking
  delay(10);

  double baz = 1.123456789;
  int ret3 = EEPROM_writeDouble(0x450, baz);
  Serial.print("Third write: ");
  Serial.print(ret3);
  Serial.print("\n");

  // writes take a few ms and are non-blocking
  delay(10);

  unsigned int boo = 23;
  int ret4 = EEPROM_writeDouble(0x400, boo);
  Serial.print("Fourth write: ");
  Serial.print(ret4);
  Serial.print("\n");
} 

void loop() 
{
  Serial.print("Loop ");
  Serial.print(loops);
  Serial.print("\n");
  
  float foo;
  EEPROM_readFloat(0x590, &foo);
  Serial.print("foo=");
  Serial.print(foo, 6);
  Serial.print("\n");

  float bar;
  EEPROM_readFloat(0x5b0, &bar);
  Serial.print("bar=");
  Serial.print(bar, 6);
  Serial.print("\n");

    if(loops == 5)
    {
      EEPROM_erase(0x450, DOUBLE_LENGTH);
    }


  double baz;
  EEPROM_readDouble(0x450, &baz);
  Serial.print("baz=");
  Serial.print(baz, 15);
  Serial.print("\n");

  double boo;
  EEPROM_readDouble(0x400, &boo);
  Serial.print("boo=");
  Serial.print(boo);
  Serial.print("\n");


  loops++;
  
  delay(1000);
}

// stored types
union storedFloat {
  float value;
  byte bytes[FLOAT_LENGTH];
};
union storedDouble {
  double value;
  byte bytes[DOUBLE_LENGTH];
};
union storedUnsignedInt {
  unsigned int value;
  byte bytes[UINT_LENGTH];
};

int EEPROM_writeBytes(int address, byte bytes[], unsigned int writeLength)
{
  // save bytes
  Wire.beginTransmission(EEPROM_DEVICE_ADDR);

  // send start address
  Wire.write(address);

  // send each byte
  for(int i = 0; i < writeLength; i++)
  {
    Wire.write(bytes[i]);
  }

  return Wire.endTransmission();
}

int EEPROM_readBytes(int address, unsigned int readLength)
{
  // indicate starting position
  Wire.beginTransmission(EEPROM_DEVICE_ADDR);
  Wire.write(address);
  Wire.endTransmission();

  // request bytes
  return Wire.requestFrom(EEPROM_DEVICE_ADDR, readLength);
}

// EEPROM methods
int EEPROM_writeFloat(int address, float value)
{
  // cast value to union structure
  union storedFloat s;
  s.value = value;

  // write bytes
  return EEPROM_writeBytes(address, s.bytes, FLOAT_LENGTH);
}

void EEPROM_readFloat(int address, float * value)
{
  // create structure
  union storedFloat s;
  
  // capture bytes
  int i = 0;
  EEPROM_readBytes(address, FLOAT_LENGTH);
  while(Wire.available())
  {
    s.bytes[i] = Wire.read();
    i++;
  }

  // populate value
  *value = s.value;
}

int EEPROM_writeDouble(int address, double value)
{
  // cast value to union structure
  union storedDouble s;
  s.value = value;

  // write bytes
  return EEPROM_writeBytes(address, s.bytes, DOUBLE_LENGTH);
}

void EEPROM_readDouble(int address, double * value)
{
  // create structure
  union storedDouble s;
  
  // capture bytes
  int i = 0;
  EEPROM_readBytes(address, DOUBLE_LENGTH);
  while(Wire.available())
  {
    s.bytes[i] = Wire.read();
    i++;
  }

  // populate value
  *value = s.value;
}

int EEPROM_writeUnsignedInt(int address, unsigned int value)
{
  // cast value to union structure
  union storedUnsignedInt s;
  s.value = value;

  // write bytes
  return EEPROM_writeBytes(address, s.bytes, UINT_LENGTH);
}

void EEPROM_readUnsignedInt(int address, unsigned int * value)
{
  // create structure
  union storedUnsignedInt s;
  
  // capture bytes
  int i = 0;
  EEPROM_readBytes(address, UINT_LENGTH);
  while(Wire.available())
  {
    s.bytes[i] = Wire.read();
    i++;
  }

  // populate value
  *value = s.value;
}

int EEPROM_erase(int address, unsigned int eraseLength)
{
  byte eraseBytes[eraseLength];
  for(int i = 0; i < eraseLength; i++) 
  {
    eraseBytes[i] = 0;
  }

  return EEPROM_writeBytes(address, eraseBytes, eraseLength);
}