EEPROM for storing settings in Arduino - Mini Project: Build & Apply

EEPROM for storing settings

📖 Scenario: You are building a small device that remembers a user's preferred brightness setting even after it is turned off. To do this, you will store the brightness value in the Arduino's EEPROM memory.

🎯 Goal: Create a program that saves a brightness setting to EEPROM and reads it back when the device starts.

📋 What You'll Learn

Use the Arduino EEPROM library

Store a brightness value (0-255) in EEPROM address 0

Read the brightness value from EEPROM on startup

Print the stored brightness value to the Serial Monitor

💡 Why This Matters

🌍 Real World

Many devices need to remember user settings like brightness or volume even after being turned off. EEPROM allows saving these settings permanently.

💼 Career

Understanding EEPROM is important for embedded systems programming and working with microcontrollers in IoT and hardware projects.

1

Setup EEPROM and initial brightness value

Include the EEPROM.h library and create a variable called brightness with the value 128.

Arduino

# Include the EEPROM library and create brightness variable
// Your code here

Hint

Use #include <EEPROM.h> to include the EEPROM library.

Create an int variable named brightness and set it to 128.

2

Write brightness to EEPROM

In the setup() function, write the brightness value to EEPROM address 0 using EEPROM.write().

Arduino

#include 

int brightness = 128;

void setup() {
  // Write brightness to EEPROM address 0
  // Your code here
}

void loop() {
}

Hint

Use EEPROM.write(address, value) to save the brightness value at address 0.

3

Read brightness from EEPROM

In the setup() function, after writing, read the brightness value back from EEPROM address 0 using EEPROM.read() and store it in the brightness variable.

Arduino

#include 

int brightness = 128;

void setup() {
  EEPROM.write(0, brightness);
  // Read brightness from EEPROM address 0
  // Your code here
}

void loop() {
}

Hint

Use brightness = EEPROM.read(0); to get the stored value back.

4

Print brightness value to Serial Monitor

Initialize the Serial communication at 9600 baud in setup() and print the brightness value using Serial.println().

Arduino

#include 

int brightness = 128;

void setup() {
  EEPROM.write(0, brightness);
  brightness = EEPROM.read(0);
  // Initialize Serial and print brightness
  // Your code here
}

void loop() {
}

Hint

Use Serial.begin(9600); to start serial communication.

Use Serial.println(brightness); to print the brightness value.

Practice

1. What is the main purpose of using EEPROM in an Arduino program?

easy

A. To increase the speed of the program

B. To store data permanently even when the power is off

C. To connect to the internet

D. To control the brightness of an LED

Solution

1. Step 1: Understand EEPROM functionality

   EEPROM memory keeps data saved even if the Arduino loses power.

2. Step 2: Compare options with EEPROM purpose

   Only To store data permanently even when the power is off describes permanent data storage, which matches EEPROM use.

3. Final Answer:

   To store data permanently even when the power is off -> Option B

4. Quick Check:

   EEPROM stores permanent data = A [OK]

Hint: EEPROM saves data without power loss [OK]

Common Mistakes:

• Confusing EEPROM with RAM (temporary memory)
• Thinking EEPROM speeds up the program
• Mixing EEPROM with internet or LED control

2. Which of the following is the correct syntax to write the value 42 to EEPROM address 10?

easy

A. EEPROM.save(42, 10);

B. EEPROM.read(10, 42);

C. EEPROM.write(10, 42);

D. EEPROM.store(10, 42);

Solution

1. Step 1: Recall EEPROM write syntax

   The correct function to save data is EEPROM.write(address, value);.

2. Step 2: Match syntax with options

   Only EEPROM.write(10, 42); uses EEPROM.write with correct parameter order.

3. Final Answer:

   EEPROM.write(10, 42); -> Option C

4. Quick Check:

   Write uses EEPROM.write(address, value) = D [OK]

Hint: Use EEPROM.write(address, value) to save data [OK]

Common Mistakes:

• Using EEPROM.read() to write data
• Using non-existent functions like EEPROM.store()
• Swapping address and value parameters

3. What will be the output of this Arduino code snippet?

EEPROM.write(5, 100);
int val = EEPROM.read(5);
Serial.println(val);

medium

A. Error

B. 0

C. 5

D. 100

Solution

1. Step 1: Understand EEPROM write and read

   The code writes 100 to address 5, then reads from address 5.

2. Step 2: Predict Serial output

   Reading address 5 returns 100, so Serial.println prints 100.

3. Final Answer:

   100 -> Option D

4. Quick Check:

   Write 100, read 100 = A [OK]

Hint: Read returns last written value at address [OK]

Common Mistakes:

• Expecting read to return address instead of value
• Confusing EEPROM.read() with EEPROM.write()
• Assuming default value 0 without write

4. Identify the error in this code that tries to save a setting to EEPROM:

int setting = 25;
EEPROM.read(0, setting);

medium

A. Using EEPROM.read() instead of EEPROM.write() to save data

B. Wrong address used, should be 1 instead of 0

C. Missing semicolon after variable declaration

D. EEPROM.read() requires three parameters

Solution

1. Step 1: Check function purpose

   EEPROM.read() reads data; EEPROM.write() saves data.

2. Step 2: Identify misuse in code

   The code uses EEPROM.read() with two parameters, which is incorrect for saving.

3. Final Answer:

   Using EEPROM.read() instead of EEPROM.write() to save data -> Option A

4. Quick Check:

   Write needs EEPROM.write(), not EEPROM.read() = C [OK]

Hint: Use EEPROM.write() to save, EEPROM.read() to get data [OK]

Common Mistakes:

• Confusing read and write functions
• Passing wrong number of parameters
• Assuming EEPROM.read() can save data

5. You want to save a user volume setting (0-255) in EEPROM address 20 and read it back on startup. Which code snippet correctly does this?

hard

A. EEPROM.write(20, volume);
int vol = EEPROM.read(20);

B. EEPROM.read(20, volume);
int vol = EEPROM.write(20);

C. EEPROM.save(20, volume);
int vol = EEPROM.load(20);

D. EEPROM.write(volume, 20);
int vol = EEPROM.read(volume);

Solution

1. Step 1: Save volume to EEPROM address 20

   Use EEPROM.write(20, volume); to store the value.

2. Step 2: Read volume back from address 20

   Use EEPROM.read(20); to get the saved value.

3. Final Answer:

   EEPROM.write(20, volume); int vol = EEPROM.read(20); -> Option A

4. Quick Check:

   Write then read from same address = B [OK]

Hint: Write then read from same EEPROM address [OK]

Common Mistakes:

• Swapping address and value parameters
• Using non-existent EEPROM.save() or EEPROM.load()
• Reading before writing data