EEPROM for storing settings in Arduino - Step-by-Step Execution

Concept Flow - EEPROM for storing settings

Start Program

↓

Initialize EEPROM

↓

Read Settings from EEPROM

↓

Use Settings in Program

↓

Modify Settings?

No→Continue Running

Yes↓

Write New Settings to EEPROM

↓

End or Loop Back

The program starts, reads settings from EEPROM, uses them, optionally updates and writes back new settings, then continues running.

Execution Sample

Arduino

#include <EEPROM.h>

int brightness = 0;

void setup() {
  brightness = EEPROM.read(0);
}

void loop() {
  // Use brightness
}

This code reads a brightness setting from EEPROM address 0 during setup and uses it in the loop.

Execution Table

Step	Action	EEPROM Address	Value Read/Written	Variable State	Notes
1	Start Program	-	-	-	Program begins execution
2	Initialize EEPROM	-	-	-	EEPROM library ready
3	Read brightness from EEPROM	0	50	brightness = 50	Read stored brightness value 50
4	Use brightness in program	-	-	brightness = 50	Brightness used for LED or display
5	Modify brightness?	-	-	-	User changes brightness to 100
6	Write new brightness to EEPROM	0	100	brightness = 100	New brightness saved to EEPROM
7	Continue running	-	-	brightness = 100	Program runs with updated brightness
8	End or loop	-	-	-	Program loops or ends

💡 Program runs continuously; EEPROM read/write happens only when settings change.

Variable Tracker

Variable	Start	After Step 3	After Step 6	Final
brightness	0 (default)	50 (read from EEPROM)	100 (updated and written)	100

Key Moments - 3 Insights

Why do we read from EEPROM in setup() and not in loop()?

Reading in setup() happens once at start, saving time and EEPROM wear. The execution_table row 3 shows reading brightness only once.

What happens if we write to EEPROM every loop without checking?

EEPROM has limited write cycles. Writing every loop (not shown here) would wear it out quickly. The table shows writing only when brightness changes (row 6).

Why do we store settings at a specific EEPROM address?

Each setting needs a unique address to avoid overwriting. Here brightness is stored at address 0 (rows 3 and 6).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of brightness after step 3?

A 100

B 0

C 50

D Undefined

💡 Hint

Check the 'Variable State' column at step 3 in the execution_table.

At which step is the new brightness value written to EEPROM?

A Step 4

B Step 6

C Step 3

D Step 2

💡 Hint

Look for the action 'Write new brightness to EEPROM' in the execution_table.

If the brightness never changes, how would the execution_table change?

A Step 6 would be skipped

B Step 3 would be skipped

C Step 5 would be 'Yes'

D Step 7 would not happen

💡 Hint

Refer to the 'Modify brightness?' decision at step 5 and the write action at step 6.

Concept Snapshot

EEPROM stores data permanently on Arduino.
Use EEPROM.read(address) to get a byte.
Use EEPROM.write(address, value) to save a byte.
Read settings once in setup(), write only when changed.
Each setting uses a unique EEPROM address.
Avoid frequent writes to protect EEPROM life.

Full Transcript

This visual execution shows how Arduino programs use EEPROM to store settings like brightness. The program starts and initializes EEPROM. It reads the brightness value from EEPROM address 0 once during setup. This value is stored in the variable brightness and used in the program loop. If the user changes brightness, the program writes the new value back to EEPROM at the same address. This prevents losing settings after power off. Writing only happens when settings change to avoid wearing out EEPROM memory. Each step shows the action, EEPROM address accessed, value read or written, and the current variable state. This helps beginners see exactly when and how EEPROM is used to save and load settings.