AT24C256 I2C Interface EEPROM Memory Module

Specifications

• Chipset: AT24C256 (256Kbit)
• Storage Capacity: 32 KBytes (32,768 x 8 bits)
• Interface: I2C (Two-Wire Interface)
• Operating Voltage: 2.7V to 5.5V (Perfect for 3.3V and 5V Logic)
• Write Endurance: > 1 Million Write Cycles
• I2C Address: Configurable via onboard jumpers (Default 0x50)
• Onboard Features: Power LED, I2C Pull-up Resistors, Write Protect Pin

Applications

• IoT Data Logging: Store sensor readings (temp, humidity) locally when Wi-Fi is down.
• Device Configuration: Save user settings, calibration data, or "Last State" memory so your robot remembers its position after a power cut.
• Security Systems: Store access logs or RFID key codes securely.
• Gaming Consoles: Create custom "Save Game" cartridges for DIY consoles.
• Industrial Counters: Log cumulative working hours or machine cycles for maintenance tracking.

Project Evolution

From "Volatile" to "Permanent" If you have mastered reading sensors with an Arduino Uno, your next hurdle is usually saving that data. Variables in your code disappear when power is lost.

• The Upgrade: Connecting this AT24C256 Module unlocks the ability to build Black Box Recorders.
• The Capability: You can now log 32,000 data points. If you log one temperature reading every 15 minutes, that’s nearly a year of data stored on a chip smaller than a coin!
• Effort Level: Intermediate. Requires understanding I2C addressing and basic binary data handling.

Virtual Technician & Wiring

Probots Logic-Safe Warning: This module operates safely on both 3.3V and 5V logic. However, always ensure your VCC matches your microcontroller's logic level to maintain signal stability.

       Pin Mapping (Standard Arduino Uno/Nano):

• SCL → A5 (Arduino SCL)
• SDA → A4 (Arduino SDA)
• VCC → 5V
• GND → GND
• Note: The module includes onboard pull-up resistors. You generally do not need to add external resistors on the breadboard.

Package Includes:

• 1 x AT24C256 I2C Interface EEPROM Memory Module.

Frequently Asked Questions (Technical FAQ)

• What is the I2C address of this module?
  The default address is usually 0x50. It can be changed to 0x50-0x57 by altering the A0, A1, A2 jumpers.
• Does this work with ESP32?
  Yes, it works perfectly with ESP32. Connect to the default I2C pins (GPIO 21 SDA, GPIO 22 SCL) and use 3.3V power.
• How much data can I actually store?
  It stores 256 Kilobits, which equals 32 Kilobytes (32,768 bytes).
• Can I connect multiple modules to one Arduino?
  Yes, by changing the address jumpers, you can daisy-chain up to 8 modules on the same I2C bus.
• Do I need external pull-up resistors?
  No, the module PCB includes onboard pull-up resistors for the SDA and SCL lines.
• What happens if I lose power?
  EEPROM is non-volatile. Your data remains safe without power for decades.
• Is there a write limit?
  Yes, EEPROM cells have a lifespan of about 1 million write cycles. Read cycles are unlimited.
• How do I protect the data from being overwritten?
  There is a Write Protect (WP) jumper/pin. If pulled High (VCC), the chip becomes Read-Only.
• Can I store audio or images on this?
  32KB is too small for meaningful audio or images. It is designed for text, numbers, and configuration flags.
• Why is my code reading all 0xFF?
  This usually means the module is not communicating. Check your wiring and verify the I2C address using an "I2C Scanner" sketch.
• Is this faster than an SD card?
  It is much faster to initialize and simpler to use for small data, but slower than SD cards for massive file transfers.
• What library should I use?
  The standard Wire.h library is sufficient, but libraries like Jack Christensen's extEEPROM make handling large data easier.
• Can I replace the chip?
  The module has an 8-pin DIP socket. You can physically pull out the AT24C256 and insert a compatible chip if needed.
• What is the page size for writing?
  The AT24C256 typically has a 64-byte page write buffer.
• Does it support 400kHz Fast Mode?
  Yes, the AT24C256 supports Standard (100kHz) and Fast (400kHz) I2C modes.
• Can I use this with Raspberry Pi?
  Yes, enable the I2C interface on your Pi configuration and use Python libraries like smbus.
• How do I clear the memory?
  You must write 0x00 or 0xFF to every address in a loop. There is no instant "format" command.
• Is the socket reliable?
  Yes, it uses a high-quality leaf-spring DIP socket for secure contact.
• What is the current consumption?
  It is very low power, typically consuming less than 1mA active and a few microamps in standby.
• Can I hot-swap the EEPROM chip?
  No, always disconnect power before removing or inserting the chip into the socket.