EEPROM read and write in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to write the value 42 to EEPROM address 0.

Arduino

#include <EEPROM.h>

void setup() {
  EEPROM.[1](0, 42);
}

void loop() {}

Drag options to blanks, or click blank then click option'

Awrite

Bread

Cupdate

Dbegin

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'read' instead of 'write' will not store data.

Using 'begin' is for initializing EEPROM, not writing.

The write function stores a byte value at a specific EEPROM address.

2fill in blank

medium

Complete the code to read a byte from EEPROM address 0 and store it in variable 'val'.

Arduino

#include <EEPROM.h>

void setup() {
  byte val = EEPROM.[1](0);
}

void loop() {}

Drag options to blanks, or click blank then click option'

Aupdate

Bwrite

Ccommit

Dread

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' instead of 'read' will overwrite data.

Using 'commit' is for saving changes in some EEPROM types, not reading.

The read function retrieves a byte stored at a given EEPROM address.

3fill in blank

hard

Fix the error in the code to update EEPROM address 1 only if the value is different.

Arduino

#include <EEPROM.h>

void setup() {
  byte newVal = 100;
  EEPROM.[1](1, newVal);
}

void loop() {}

Drag options to blanks, or click blank then click option'

Awrite

Bupdate

Cread

Dcommit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' always writes even if value is the same, reducing EEPROM life.

Using 'read' does not write data.

The update function writes a byte only if it differs from the current EEPROM value, saving write cycles.

4fill in blank

hard

Fill both blanks to write value 55 to EEPROM address 2 and then read it back into 'val'.

Arduino

#include <EEPROM.h>

void setup() {
  EEPROM.[1](2, 55);
  byte val = EEPROM.[2](2);
}

void loop() {}

Drag options to blanks, or click blank then click option'

Awrite

Bread

Cupdate

Dcommit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'update' instead of 'write' is okay but not required here.

Using 'commit' is not needed for basic EEPROM operations.

First, write stores the value, then read retrieves it.

5fill in blank

hard

Fill all three blanks to update EEPROM address 3 with 77 only if different, then read it into 'val', and finally write 88 to address 4.

Arduino

#include <EEPROM.h>

void setup() {
  EEPROM.[1](3, 77);
  byte val = EEPROM.[2](3);
  EEPROM.[3](4, 88);
}

void loop() {}

Drag options to blanks, or click blank then click option'

Awrite

Bread

Cupdate

Dcommit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' instead of 'update' for the first blank causes unnecessary writes.

Mixing up read and write functions.

Use update to write only if different, read to get the value, and write to store 88.

Practice

1. What does EEPROM.write(address, value) do in Arduino?

easy

A. Stores a byte value at the specified EEPROM address

B. Reads a byte value from the specified EEPROM address

C. Deletes all data from EEPROM

D. Initializes the EEPROM memory

Solution

1. Step 1: Understand EEPROM.write function

   The function EEPROM.write(address, value) saves a byte value at the given address in EEPROM memory.

2. Step 2: Differentiate from EEPROM.read

   EEPROM.read(address) is used to read data, not write it.

3. Final Answer:

   Stores a byte value at the specified EEPROM address -> Option A

4. Quick Check:

   EEPROM.write saves data [OK]

Hint: Write saves data, read retrieves data from EEPROM [OK]

Common Mistakes:

• Confusing write with read function
• Thinking EEPROM.write clears memory
• Assuming EEPROM.write initializes EEPROM

2. Which of the following is the correct syntax to read a byte from EEPROM at address 10?

easy

A. EEPROM.get(10);

B. EEPROM.write(10);

C. EEPROM.readByte(10);

D. EEPROM.read(10);

Solution

1. Step 1: Identify correct EEPROM read syntax

   The correct function to read a byte from EEPROM is EEPROM.read(address).

2. Step 2: Check options for exact match

   Only EEPROM.read(10); matches the correct syntax.

3. Final Answer:

   EEPROM.read(10); -> Option D

4. Quick Check:

   EEPROM.read(address) reads byte [OK]

Hint: Use EEPROM.read(address) to get stored byte [OK]

Common Mistakes:

• Using EEPROM.write to read data
• Using non-existent EEPROM.readByte function
• Confusing EEPROM.get with EEPROM.read

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

EEPROM.write(5, 42);
byte val = EEPROM.read(5);
Serial.println(val);

medium

A. 0

B. 42

C. 5

D. Undefined behavior

Solution

1. Step 1: Write value 42 at EEPROM address 5

   The code stores the byte 42 at address 5 using EEPROM.write(5, 42);.

2. Step 2: Read the value back from address 5

   EEPROM.read(5) reads the stored value, which is 42.

3. Final Answer:

   42 -> Option B

4. Quick Check:

   Write 42, read 42 [OK]

Hint: Write then read same address returns stored value [OK]

Common Mistakes:

• Assuming EEPROM.read returns address instead of value
• Forgetting to write before reading
• Expecting default 0 without writing

4. Identify the error in this code snippet:

EEPROM.write(1024, 100);
byte val = EEPROM.read(1024);
Serial.println(val);

medium

A. Serial.println cannot print byte values

B. EEPROM.write requires two arguments

C. Address 1024 is out of EEPROM range

D. EEPROM.read cannot be assigned to byte

Solution

1. Step 1: Check EEPROM address range

   Typical Arduino EEPROM size is 1024 bytes, so address 1024 is out of range (valid addresses are 0-1023).

2. Step 2: Validate other code parts

   EEPROM.write has correct arguments, EEPROM.read returns byte, and Serial.println can print bytes.

3. Final Answer:

   Address 1024 is out of EEPROM range -> Option C

4. Quick Check:

   EEPROM address must be within 0-1023 [OK]

Hint: EEPROM addresses start at 0, max 1023 on typical boards [OK]

Common Mistakes:

• Using address equal to EEPROM size
• Assuming EEPROM size is larger than actual
• Misunderstanding Serial.println capabilities

5. You want to store a user's high score (an integer between 0 and 1000) in EEPROM. Which approach correctly saves and reads this value?

hard

A. Use EEPROM.put(address, highScore); and EEPROM.get(address, highScore);

B. Use EEPROM.write(address, highScore); and EEPROM.read(address);

C. Use EEPROM.write(address, highScore % 256); only

D. Use EEPROM.read(address); to save and EEPROM.write(address, highScore); to read

Solution

1. Step 1: Understand data size and EEPROM functions

   High score is an integer (2 bytes), so EEPROM.write (1 byte) is insufficient to store full value.

2. Step 2: Use EEPROM.put and EEPROM.get for multi-byte data

   EEPROM.put(address, highScore); saves the entire integer, and EEPROM.get(address, highScore); reads it back correctly.

3. Final Answer:

   Use EEPROM.put(address, highScore); and EEPROM.get(address, highScore); -> Option A

4. Quick Check:

   Use put/get for multi-byte data [OK]

Hint: Use EEPROM.put/get for integers, write/read for bytes [OK]

Common Mistakes:

• Using EEPROM.write for multi-byte integers
• Not reading back with EEPROM.get
• Mixing read and write roles