AT24C02 EEPROM Storage Module I2C Interface Smart Car Accessory Data Memory

AT24C02 EEPROM memory module with I2C interface (SDA/SCL). 2Kbit (256 bytes) storage. Data retains after power loss, 1 million write cycles. Ideal for smart car accessories, device parameter storage, config saving, MCU external memory. 5V/3.3V compatible

AT24C02 EEPROM Storage Module Application features:

◆ Main Chip
AT24C02 2Kbit EEPROM

◆ Storage Capacity
256 bytes (2Kbit)

◆ Communication Interface
I2C (SDA / SCL)

◆ I2C Address
0x50 (configurable via A0/A1/A2 pins)

◆ Write Endurance
1,000,000 cycles

◆ Data Retention
100+ years

◆ Supply Voltage
2.7V – 5.5V (3.3V/5V compatible)

◆ Onboard Interface

• VCC / GND

• SDA / SCL

• A0 / A1 / A2 (address jumpers)

◆ Typical Applications

• Smart car accessory parameter storage

• Device configuration data saving

• Microcontroller external memory

• User setting memory

• Industrial parameter backup

• Access control system data

◆ Key Advantages

• I2C interface (only 2 signal wires)

• Non-volatile data retention

• Configurable I2C address (multiple devices on one bus)

• Compact size

• Compatible with Arduino/STM32/Raspberry Pi

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Quantity(Pieces)	1 ~ 30000	30001 ~ 300000	> 300000
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FAQ

1. What is the AT24C02 EEPROM module and its key specifications?
This module is a small non‑volatile memory board built around the Atmel AT24C02 chip, providing 2 Kbits (256 bytes) of electrically erasable programmable read‑only memory. It communicates over an I2C bus and is widely used to store configuration parameters, calibration data, and small logs in embedded systems. Key specifications include:

• Memory size: 2 Kbits (256 bytes), organised as 32 pages of 8 bytes.
• Interface: I2C (2‑wire serial), supports up to 400 kHz (Fast Mode).
• Default I2C address: 0x50 (7‑bit), configurable via A0/A1/A2 address pins (up to 8 devices on one bus).
• Operating voltage: 2.5 V – 5.5 V DC (compatible with 3.3 V and 5 V systems).
• Write endurance: 1 million write cycles per byte.
• Data retention: over 100 years.
• Dimensions: typically 10 mm × 10 mm module with pin headers.

2. How do I connect the AT24C02 module to an Arduino, ESP32, or other MCU?
Wiring uses the I2C bus. Connect VCC → 3.3 V or 5 V, GND → GND, SDA → SDA (A4 on Arduino Uno, GPIO21 on ESP32), and SCL → SCL (A5 on Arduino Uno, GPIO22 on ESP32). The module usually includes on‑board pull‑up resistors on SDA and SCL, so external resistors are not required for short connections. The three address pins (A0, A1, A2) are typically pulled LOW on the module, setting the 7‑bit address to 0x50. After wiring, run an I2C scanner sketch to verify the device is detected at address 0x50.

3. What is the I2C address of the AT24C02, and how do I change it?
The base 7‑bit I2C address is 0x50. The three address pins (A0, A1, A2) allow you to set the three least significant bits of the address, enabling up to 8 AT24C02 devices on the same bus (addresses 0x50 through 0x57). On most modules, these pins are connected to GND via solder pads or jumpers, giving the default address 0x50. To change the address, cut the relevant GND trace and connect the pin to VCC. For example, connecting A0 to VCC changes the address to 0x51. Always power‑cycle the module after changing the address configuration.

4. How do I read from and write to the AT24C02 using Arduino?
Use the built‑in Wire library. To write a single byte to address 0x00:

• Wire.beginTransmission(0x50);
• Wire.write(0x00); // memory address
• Wire.write(value); // data byte
• Wire.endTransmission();
• delay(5); // wait for write cycle (max 5 ms)

To read from address 0x00:

• Wire.beginTransmission(0x50);
• Wire.write(0x00);
• Wire.endTransmission();
• Wire.requestFrom(0x50, 1);
• byte val = Wire.read();

You can also perform page writes of up to 8 bytes at a time (within a single page boundary) for faster bulk storage.

5. What is the maximum write speed, and why do I need a delay after writing?
The AT24C02 has an internal write cycle time of up to 5 ms. After issuing a write command, the chip is busy and will not respond to further I2C requests until the write is complete. In your code, you must insert a delay(5) after each write operation, or use a polling loop that checks for an I2C acknowledgement. The data sheet specifies a maximum of 5 ms, but typical writes complete in 1–2 ms. A page write of 8 bytes takes the same 5 ms as a single‑byte write.

6. What is the difference between the AT24C02 and the AT24C04/AT24C08/AT24C16?
The primary difference is memory capacity:

• AT24C02: 2 Kbits (256 bytes).
• AT24C04: 4 Kbits (512 bytes).
• AT24C08: 8 Kbits (1 KB).
• AT24C16: 16 Kbits (2 KB).

Larger chips use additional I2C address bits to access the extra memory, so the maximum number of devices on a single bus decreases (e.g., only one AT24C16 can be used on a bus because it uses all three address pins for memory addressing). The AT24C02 is the most common choice for storing small amounts of configuration data. All variants share the same write endurance and retention specifications.

7. Can the AT24C02 be used with a 3.3 V MCU like ESP32 or Raspberry Pi?
Yes. The AT24C02 operates from 2.5 V to 5.5 V, so it can be powered directly from a 3.3 V supply. The I2C pins are 5 V tolerant, meaning you can safely connect a 3.3 V MCU to a 5 V‑powered AT24C02 module without a level shifter. Most modules include pull‑up resistors connected to VCC; if you power the module at 3.3 V, the pull‑ups will also be at 3.3 V, which is safe for 3.3 V MCUs. For Raspberry Pi, the module works identically using the smbus2 or pigpio libraries.

8. What are the typical applications of the AT24C02 EEPROM module?
It is used wherever a small amount of non‑volatile data must be preserved across power cycles. Typical applications include storing device serial numbers, calibration constants for sensors, user settings, password tokens, last‑state memory for appliances, and configuration files for Arduino/ESP32 projects. In smart cars and robotics, it can save PID tuning parameters, motor zero positions, and fail‑safe states. Because the data survives power‑off and the chip is extremely simple to interface, it is a staple component in embedded designs that need a few bytes of permanent storage.

9. How can I extend the lifespan of the AT24C02 if I need to write data very frequently?
The AT24C02 is rated for 1 million write cycles per byte, which is sufficient for most infrequent configuration updates. If you need to write data very often (e.g., logging sensor readings every second), you should implement a wear‑levelling strategy. This can be done by writing data sequentially across memory addresses and wrapping around, rather than always overwriting the same location. Another technique is to buffer data in RAM and only flush to EEPROM periodically. For ultra‑high‑frequency logging, an SD card or a larger EEPROM with wear‑levelling firmware may be more appropriate.

10. Why is my AT24C02 not detected on the I2C bus, or write/read operations fail?
Common causes and solutions:

• Power supply: check that VCC is within 2.5 V – 5.5 V and GND is connected.
• Pull‑up resistors: ensure that SDA and SCL have pull‑up resistors (4.7 kΩ to VCC). Most modules include them, but if missing, I2C will not work.
• Address mismatch: run an I2C scanner to verify the actual address; check A0/A1/A2 jumper settings.
• Write delay: ensure you insert a 5 ms delay after each write operation.
• Noise: long I2C cables can cause communication errors; keep wires short (< 20 cm) or lower the bus speed to 100 kHz.
• Bad solder joints: inspect the module for cold solder joints, especially on the address pins and the AT24C02 chip.