RfidDb

RfidDb provides a database that contains 32 bit identifiers and optionally associated names which can be used with an RFID reader to control access. The identifiers and names are stored in EEPROM and will persist across restarts.

Creating and initialising RfidDb

An RfidDb must be created with the maximum size of the database and the EEPROM location at which the database starts. Optionally, the maximum length of the name field can be specified in the constructor. If this is not specified (or is zero), then then storage of names will be disabled. The name length includes a null terminating character.

To find the amount of EEPROM required for the database, add 4 to the maximum length of the name, multiply by the maximum number of entries and the add two bytes. For example, a 16 entry database with 8 character names takes 194 bytes; ((4 + 8) * 16) + 2.

The database must be initialised by calling the begin() method prior to use. This is generally done in the setup method.

To create a database that can hold 16 identifiers, with storage starting at byte 0 of EEPROM without storing names:

RfidDb db = RfidDb(16, 0);

void setup() {
  db.begin();
}

To create a database that can hold 8 identifiers, with storage starting at byte 25 of EEPROM, with a maximum of 8 character names:

RfidDb db = RfidDb(8, 24, 8);

void setup() {
	db.begin();
}

ESP8266/ESP32

If using the library with ESP8266 or ESP32 platforms, you must call EEPROM.begin() before RfidDb.begin(). The method RfidDb.dbSize() is useful to determine the maximum size of the RFID database. For example:

RfidDb db = Rfid(8, 0, 24);

void setup() {
	EEPROM.begin(db.dbSize());
	db.begin();
}

Database Methods

The public methods available on the RfidDb are described below.

maxSize

Returns the maximum number of identifiers that can be held in the database.

db.maxSize();

dbSize

Returns the total size of the database in bytes.

db.dbSize();

maxNameLength

Returns the maximum length of the name field (including the terminating null)

db.maxNameLength();

count

Returns the number of identifiers currently in the database.

db.count();

insert

Inserts a 32 bit identifier and optionally a name into the database. Returns true if the insert was successful, or the identifier already existed in the database and false if the identifier could not be inserted due to a full database.

Names which are longer than the maximum name length are truncated to fit in the database. If the database is not storing names and a name is stored, then the name is silently ignored. If no name is stored and the database stores names, then the name is set to the null string.

To insert an id only:

if (db.insert(10042)) {
  Serial.println("Inserted or already existed");
} else {
  Serial.println("Insert failed");
}

To insert an id and name:

if (db.insert(10042, "ABCD")) {
  Serial.println("Inserted or already existed");
} else {
  Serial.println("Insert failed");
}

remove

Removes an entry identifed by the given 32 bit identifier from the database. If the database is empty or thee identifier was not in the database then this method does nothing.

db.remove(10042);

getId

Returns the identifier at the specified zero-based position. The caller must provide an unsigned 32-bit integer which this function will populate with the identifier value. The method returns true if the get was successful and false if the get was unsuccessful due to the postion being out of range.

uint32_t id;
if (db.get(4, id)) {
  Serial.print("Get successful. id = ");
  Serial.println(id);
} else {
  Serial.println("Get unsuccessful");
}

getName

Returns the name at the specified zero based position. The caller must supply a char[] to receive the name of at least the maximum name length of the database. The method returns true if the database stores name and the supplied postion is in range (between 0 and count() - 1). The method returns false if the database does not store names or the positon is out of range.

char name[db.maxNameLength()];
if (db.get(4, name)) {
	Serial.print("Get successful. name = ");
	Serial.println(name);
} else {
	Serial.println("Get unsuccessful");
}

contains

Returns true if the database contains the given identifier, false otherwise.

if (db.contains(10042)) {
  Serial.println("In database");
} else {
  Serial.println("Not in database");
}

contains24

Returns true if the low order 24-bits of the specified id match the low order 24 bits of any id in the databse. This us useful if 32 bit ids are stored in the database and the ids are read using a Wiegand26 reader which returns 24 bits.

if (db.contains24(10042)) {
  Serial.println("In database");
} else {
  Serial.println("Not in database");
}