How do I write and read internal EEPROM?

Question

I am working on an Arduino Mega 2560. I want to read and write the internal EEPROM.

Can I use EEPROM.get()/EEPROM.put()?

I want to store 3 things in EEPROM:

1. Boolean status.

2. String password: length 5 digits.

3. String Mobile number: length 10 digits.

Answer 1

How do I write and read internal EEPROM? Can I use EEPROM.get()/EEPROM.put()?

Yes, the Arduino Reference for EEPROM contains an example of what you are asking for. Below is a simple rewrite of the example for EEPROMGet for your info.

struct MyObject{
  bool status;
  char password[6];
  char mobileNumber[11];
};

void setup() 
{

  int eeAddress = 0; //EEPROM address to start reading from

  Serial.begin( 9600 );
  while (!Serial) ;

  MyObject customVar; //Variable to store custom object read from EEPROM.
  EEPROM.get(eeAddress, customVar);

  Serial.println(F("Read custom object from EEPROM: "));
  Serial.println(customVar.status);
  Serial.println(customVar.password);
  Serial.println(customVar.mobileNumber);
}

For more details and examples see https://www.arduino.cc/en/Reference/EEPROM.

Cheers!

Answer 2

Avoid the 'String' object, use a character array of fixed length. You might want to add one extra byte for the zero-terminator. Put everything in a 'struct' and then you can use the EEPROM.get() and EEPROM.put() to read and write the complete struct. I prefer a struct to keep the data from EEPROM together. That makes it easier to add a checksum and a version number for the data. When something is wrong with the data from EEPROM then default values could be used.

Instead of a struct, you can also read and write the seperate items. The EEPROM.get() and EEPROM.put() should be able to use a character array of fixed length.