DAOKAI AT24C256 I2C EEPROM Memory Module User Manual

1. Introduction

This manual provides comprehensive instructions for the DAOKAI AT24C256 I2C EEPROM Memory Module. This breakout board is designed to facilitate the integration of an EEPROM (Electrically Erasable Programmable Read-Only Memory) into your electronic projects. The AT24C256 chip offers 256 kilobits (32 kilobytes) of non-volatile data storage, organized into 8192 words of 8 bits, accessible via the common I2C serial interface. It is ideal for applications requiring persistent data storage, such as configuration settings, logging, or small data tables.

Figure 1.1: Overview of the AT24C256 I2C EEPROM Memory Module. This image shows the compact blue PCB with the AT24C256 chip in a DIP socket, along with header pins for connection and other components.

2. Package Contents

Verify that all items listed below are included in your package. If any items are missing or damaged, please contact your supplier.

• 5 x AT24C256 I2C interface EEPROM Memory Module
• 1 x 20pin Female to Male Dupont Cable

Figure 2.1: Contents of the package, showing multiple AT24C256 modules and a set of Dupont cables.

3. Product Features and Specifications

3.1. Key Features

• AT24C256 Chip: Onboard 8P-chip carrier, supporting AT24C256 series chips.
• I2C Interface: Communication handled through a 2-pin I2C interface.
• Address Selection: I2C address can be set by A0, A1, A2 jumpers for addresses in the range of 0x50 - 0x57.
• Power Indicator: Onboard LED indicator for power status.
• Pull-up Resistors: Onboard pull-up resistors for I2C communications.
• Pin Accessibility: All pins are clearly labeled and led out for easy connection.
• Write Protection: Dedicated write-protect pin (WP) with direct jumper settings.
• Storage Capacity: 256 kilobits (32 kilobytes) of EEPROM storage.
• Compact Design: 8-pin double-row in-line package, compact structure.

Figure 3.1: Illustration of the AT24C256 chip and its key features, including supported working voltages and internal structure details.

3.2. Technical Specifications

Figure 3.2: Physical dimensions of the AT24C256 I2C EEPROM Memory Module, showing its length and width.

4. Pin Definition and Schematic

4.1. Pin Definition

The module features a standard pinout for easy integration. Understanding each pin's function is crucial for proper operation.

• A0, A1, A2: Address selection inputs. These pins are used to set the I2C slave address of the EEPROM. By connecting these pins to GND or VCC, you can select one of eight possible addresses (0x50 to 0x57). In a serial bus structure, multiple AT24C256 ICs can be connected by using different address settings. For example, if A1 is 0 when floating.
• SCL: Serial Clock Input. This pin provides the clock signal for I2C communication. The rising edge of SCL writes data to the memory, and the falling edge reads data from the memory.
• SDA: Bidirectional Serial Data Input/Output. This pin is used for data exchange between the memory module and the microcontroller.
• WP: Write Protect Input. When this pin is connected to GND, write operations are allowed. When connected to VCC, all write memory operations are disabled, protecting the data. If not connected, the chip is internally pulled down to ground, enabling write operations by default.
• VCC: Power Supply. Connect to the positive voltage supply (e.g., 3.3V or 5V).
• GND: Ground. Connect to the common ground of your system.
• NC: Not Connected / Empty.

Figure 4.1: Detailed pinout diagram of the AT24C256 chip and its corresponding functions on the module.

4.2. Product Schematic

The following schematic illustrates the internal connections and components of the AT24C256 I2C EEPROM Memory Module. This can be useful for advanced users or for troubleshooting.

Figure 4.2: Electrical schematic of the AT24C256 module, showing the AT24C256 chip, pull-up resistors (R12, R13), and pin connections.

5. Setup and Connection

This section guides you through the process of connecting the AT24C256 EEPROM module to your microcontroller (e.g., Arduino).

5.1. Basic Wiring

1. Power Connection: Connect the VCC pin of the module to the 3.3V or 5V power supply output of your microcontroller. Connect the GND pin of the module to the ground (GND) of your microcontroller.
2. I2C Connection:
   • Connect the SDA pin of the module to the SDA (Serial Data Line) pin of your microcontroller.
   • Connect the SCL pin of the module to the SCL (Serial Clock Line) pin of your microcontroller.
3. Address Selection (A0, A1, A2): These pins determine the I2C address. For a single module, you can leave them floating (which typically defaults to 0x50 if internally pulled low) or connect them to GND for 0x50. If using multiple modules on the same I2C bus, connect A0, A1, A2 to VCC or GND in different combinations to assign unique addresses (0x50 to 0x57).
4. Write Protect (WP): For normal read/write operations, ensure the WP pin is connected to GND. To prevent accidental writes and protect data, connect the WP pin to VCC.

Figure 5.1: Close-up views of the module, highlighting the powered pins and the onboard power indicator LED.

5.2. Example Connection (Arduino)

For Arduino Uno/Nano/Mega:

• Module VCC → Arduino 5V (or 3.3V if your AT24C256 chip supports it)
• Module GND → Arduino GND
• Module SDA → Arduino A4 (SDA)
• Module SCL → Arduino A5 (SCL)
• Module A0, A1, A2 → Connect to GND for default address 0x50, or configure as needed.
• Module WP → Connect to GND for read/write operations.

6. Operating Principles and Programming

The AT24C256 module communicates using the I2C protocol. This section outlines the basic principles for interacting with the EEPROM.

6.1. I2C Communication Basics

The I2C protocol is a two-wire serial communication bus. It operates with a master (your microcontroller) and one or more slaves (the EEPROM module).

• Slave Address: The AT24C256 has a base I2C address of 0x50. The A0, A1, A2 pins allow you to modify the last three bits of this address, enabling up to 8 unique addresses (0x50 to 0x57) for multiple devices on the same bus.
• Data Transfer: Data is transferred in 8-bit bytes. Each byte is followed by an Acknowledge (ACK) or Not Acknowledge (NACK) bit.
• Memory Addressing: The AT24C256 has 32,768 bytes (32KB) of memory. To access a specific byte, you send a 16-bit memory address after the device address.

6.2. Read/Write Operations

Most microcontrollers have built-in I2C (Wire) libraries that simplify communication.

• Writing Data:
  1. Start I2C communication.
  2. Send the device write address (e.g., 0x50).
  3. Send the 16-bit memory address (high byte then low byte) where you want to write.
  4. Send the data byte(s) you wish to store.
  5. Stop I2C communication.

  Note: The AT24C256 supports page writes of up to 64 bytes. If writing more than 64 bytes, you must perform multiple page writes.

• Reading Data:
  1. Start I2C communication.
  2. Send the device write address (e.g., 0x50).
  3. Send the 16-bit memory address from where you want to read.
  4. Restart I2C communication.
  5. Send the device read address (e.g., 0x51).
  6. Read the data byte(s).
  7. Stop I2C communication.

7. Application Examples

The AT24C256 EEPROM module is versatile and can be used in various projects requiring non-volatile data storage.

• Configuration Storage: Store user settings, calibration data, or device configuration parameters that need to persist even after power loss.
• Data Logging: Record sensor readings, event logs, or operational data in embedded systems.
• Lookup Tables: Store fixed data tables that are frequently accessed by the microcontroller.
• Bootloader Parameters: Save parameters for bootloaders or firmware updates.

Figure 7.1: An illustrative setup showing the AT24C256 module connected to an Arduino board, potentially used for storing servo motor positions or other project data.

8. Troubleshooting

If you encounter issues with your AT24C256 EEPROM module, consider the following troubleshooting steps:

• Module Not Detected (I2C Scan Fails):
  • Check Wiring: Ensure VCC, GND, SDA, and SCL connections are correct and secure.
  • Power Supply: Verify the module is receiving the correct voltage (e.g., 5V or 3.3V). The onboard LED should light up if powered.
  • I2C Address: Confirm the I2C address used in your code matches the physical A0, A1, A2 pin settings on the module.
  • Pull-up Resistors: While the module has onboard pull-ups, ensure they are sufficient for your bus length and other devices. If using a long bus or many devices, external pull-ups (4.7kΩ to 10kΩ) on SDA and SCL to VCC might be needed.
  • WP Pin: Ensure the WP pin is correctly configured (connected to GND for write operations).
• Data Corruption or Inconsistent Reads:
  • Power Stability: Unstable power supply can lead to data issues. Ensure a clean and stable power source.
  • Timing Issues: Ensure your microcontroller's I2C clock speed is compatible with the AT24C256 (typically up to 400kHz).
  • Write Cycle Time: After a write operation, the EEPROM requires a short time (typically 5ms) to complete the write cycle before it can be read or written to again. Ensure your code accounts for this delay.
  • WP Pin: Double-check the WP pin status. If it's high (VCC), write operations will fail silently.
• Module Overheating:
  • Incorrect Voltage: Ensure you are not supplying a voltage higher than the maximum rated voltage for the chip (typically 5.5V).
  • Short Circuits: Check for any accidental short circuits on the module or in your wiring.

9. Maintenance and Care

The AT24C256 EEPROM module is a robust electronic component, but proper care can extend its lifespan and ensure reliable operation.

• Handling: Handle the module by its edges to avoid touching the electronic components, which can be sensitive to static electricity.
• Storage: Store the module in an anti-static bag or container when not in use, especially in dry environments.
• Environment: Avoid exposing the module to extreme temperatures, high humidity, dust, or corrosive substances.
• Cleaning: If necessary, gently clean the PCB with a soft, dry brush or a lint-free cloth. Avoid using liquids or harsh chemicals.
• Power Off Before Connecting/Disconnecting: Always ensure power is disconnected from your circuit before connecting or disconnecting the module to prevent damage.

10. Warranty and Support

Information regarding product warranty and customer support is not available in the provided product data. Please refer to the seller's or manufacturer's official website for details on warranty terms, technical support, and return policies.

For further assistance, you may contact DAOKAI customer service through their official channels.