I2C_EEPROM

Arduino Library for external I2C EEPROM - 24LC256, 24LC64

Description

This library is to access external I2C EEPROM up to 64KB (= 512 Kbit) in size.

The I2C_eeprom_cyclic_store interface is documented here

Interface

Constructor

• I2C_eeprom(deviceAddress) constructor.
• bool begin() initializes the I2C bus and checks if the device is available on the I2C bus.
• bool begin(sda, scl) idem for ESP32 / ESP8266 and alike.
• bool isConnected() test to see if device is on the bus.

Core functions

• int writeByte(memoryAddress, value) write a single byte to the specified memory address.
• int writeBlock(memoryAddress, buffer, length) write a buffer starting at the specified memory address.
• int setBlock(memoryAddress, value, length) writes the same byte to length places starting at the specified memory address. Returns 0 if OK.
• uint8_t readByte(memoryAddress) read a single byte from a given address
• uint16_t readBlock(memoryAddress, buffer, length) read length bytes into buffer starting at specified memory address. Returns the number of bytes read, which should be length.
• int updateByte(memoryAddress, value) write a single byte, but only if changed. Returns 0 if value was same or write succeeded.

Other

• uint32_t getDeviceSize() idem
• uint8_t getPageSize() idem
• uint32_t getLastWrite() idem
• uint32_t determineSize(bool debug = false)
  function that determins the size of the EEPROM by detecting when a memory address is folded upon memory address 0. It is based upon the observation that memory wraps around. The debug flag gives some output to Serial.

Warning: this function has changed (again) in 1.4.0

Testresults

returns	Type	Memory	Page Size	Notes
0	-			connect error, check device address / wiring
65536	24LC512	64 KB	128
32768	24LC256	32 KB	64
16384	24LC128	16 KB	64
8192	24LC64	8 KB	32
4096	24LC32	4 KB	32	not tested with hardware
2048	24LC16	2 KB	16
1024	24LC08	1 KB	16
512	24LC04	512 b	16
256	24LC02	256 b	8
128	24LC01	128 b	8

The function cannot detect smaller than 128 bit EEPROMS (yet).

Limitation

The library does not offer multiple EEPROMS as one continuous storage device.

Future

• look into support of > 64KB EEPROM
• improve error handling, write functions should return bytes written or so.
• what can we do with the print interface? (investigate)
• Wire0 .. WireN support
• investigate multi-EEPROM storage,
• investigate format / clear all function.

Operational

See examples