LCD cursor positioning in Arduino - Step-by-Step Execution

Concept Flow - LCD cursor positioning

Start

↓

Initialize LCD

↓

Set Cursor Position (col, row)

↓

Print Text at Cursor

↓

End

The program starts by initializing the LCD, then sets the cursor to a specific column and row before printing text there.

Execution Sample

Arduino

lcd.begin(16, 2);
lcd.setCursor(4, 1);
lcd.print("Hi!");

This code sets up a 16x2 LCD, moves the cursor to column 4, row 1, and prints 'Hi!' at that position.

Execution Table

Step	Action	Cursor Position (col,row)	Output on LCD
1	lcd.begin(16, 2)	(0,0)	LCD cleared, ready
2	lcd.setCursor(4, 1)	(4,1)	Cursor moved to col 4, row 1
3	lcd.print("Hi!")	(6,1)	'Hi!' appears starting at col 4, row 1
4	End of code	(6,1)	Final display with 'Hi!' at row 1, col 4

💡 Code ends after printing 'Hi!' at the specified cursor position.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Cursor Position	(0,0)	(0,0)	(4,1)	(6,1)	(6,1)
LCD Display	"" (empty)	Cleared	Cleared	" Hi" on row 1	" Hi" on row 1

Key Moments - 2 Insights

Why does the cursor position change after printing 'Hi!'?

Because lcd.print() moves the cursor forward by the number of characters printed, as shown in step 3 of the execution_table.

What happens if you set the cursor outside the LCD size?

The cursor will not move correctly or text may not appear; the lcd.setCursor() expects column and row within the LCD dimensions, as initialized in step 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is the cursor position after step 2?

A (0,0)

B (4,1)

C (6,1)

D (1,4)

💡 Hint

Check the 'Cursor Position' column in row for step 2 in execution_table.

At which step does the LCD display show 'Hi!'?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Output on LCD' column in execution_table rows.

If you change lcd.setCursor(4, 1) to lcd.setCursor(0, 0), where will 'Hi!' appear?

A At column 4, row 1

B At column 6, row 1

C At column 0, row 0

D It will not appear

💡 Hint

Refer to how lcd.setCursor sets the starting position before printing in execution_table step 2.

Concept Snapshot

lcd.begin(cols, rows) initializes the LCD size.
lcd.setCursor(col, row) moves the cursor to a position.
lcd.print(text) prints text starting at cursor and moves cursor forward.
Cursor position is zero-based: col 0 is leftmost, row 0 is top.
Setting cursor outside bounds causes no visible output.
Use these to control where text appears on the LCD.

Full Transcript

This example shows how to position the cursor on an LCD using Arduino code. First, the LCD is initialized with lcd.begin(16, 2) for a 16 columns by 2 rows display. The cursor is then moved to column 4, row 1 using lcd.setCursor(4, 1). When lcd.print("Hi!") runs, it prints the text starting at that cursor position and moves the cursor forward by the length of the text. The execution table tracks these steps, showing cursor positions and LCD output after each action. Key points include understanding that the cursor moves after printing and that positions are zero-based. The visual quiz tests understanding of cursor positions and output locations. The snapshot summarizes the commands and their effects for quick reference.

Practice

1. What does the Arduino command lcd.setCursor(0, 1) do on a 16x2 LCD?

easy

A. Clears the LCD screen

B. Moves the cursor to the second column of the first row

C. Moves the cursor to the first column of the second row

D. Prints text at the current cursor position

Solution

1. Step 1: Understand lcd.setCursor parameters

   The first number is the column (starting at 0), the second is the row (starting at 0).

2. Step 2: Apply to given command

   lcd.setCursor(0, 1) moves the cursor to column 0 (first column) and row 1 (second row).

3. Final Answer:

   Moves the cursor to the first column of the second row -> Option C

4. Quick Check:

   Columns and rows start at zero = first column, second row [OK]

Hint: Remember columns and rows start at zero [OK]

Common Mistakes:

• Thinking rows start at 1 instead of 0
• Confusing column and row order
• Assuming setCursor prints text

2. Which of the following is the correct syntax to set the cursor to the third column and first row on an LCD?

easy

A. lcd.setCursor(3, 1);

B. lcd.setCursor(1, 2);

C. lcd.setCursor(0, 3);

D. lcd.setCursor(2, 0);

Solution

1. Step 1: Recall zero-based indexing

   Columns and rows start at 0, so third column is 2, first row is 0.

2. Step 2: Match parameters to correct syntax

   lcd.setCursor(2, 0) sets cursor to third column, first row.

3. Final Answer:

   lcd.setCursor(2, 0); -> Option D

4. Quick Check:

   Third column = 2, first row = 0 [OK]

Hint: Count columns and rows from zero [OK]

Common Mistakes:

• Using 1-based indexing for columns or rows
• Swapping column and row values
• Missing semicolon at end

3. What will be the output on a 16x2 LCD after running this code?

lcd.setCursor(5, 0);
lcd.print("Hi");
lcd.setCursor(0, 1);
lcd.print("Bye");

medium

A. First row: 'Hi' starting at first column, second row: 'Bye' starting at first column

B. First row: ' Hi' (5 spaces then Hi), second row: 'Bye' starting at first column

C. First row: 'Hi' starting at sixth column, second row: 'Bye' starting at sixth column

D. First row: ' Hi' (5 spaces then Hi), second row: ' Bye' (5 spaces then Bye)

Solution

1. Step 1: Analyze first setCursor and print

   lcd.setCursor(5, 0) moves cursor to column 5, row 0. Printing "Hi" starts at column 5 on first row.

2. Step 2: Analyze second setCursor and print

   lcd.setCursor(0, 1) moves cursor to first column, second row. Printing "Bye" starts there.

3. Final Answer:

   First row: ' Hi' (5 spaces then Hi), second row: 'Bye' starting at first column -> Option B

4. Quick Check:

   Cursor moves control print position [OK]

Hint: Cursor sets exact print start position [OK]

Common Mistakes:

• Assuming print always starts at first column
• Confusing row and column numbers
• Ignoring spaces before printed text

4. Identify the error in this Arduino code snippet for LCD cursor positioning:

lcd.setCursor(16, 0);
lcd.print("Hello");

medium

A. Column index 16 is out of range for a 16-column LCD

B. Row index 0 is invalid, should start at 1

C. Missing lcd.begin() before setCursor

D. lcd.print() cannot print strings

Solution

1. Step 1: Check column index range

   Columns start at 0, so valid columns are 0 to 15 for a 16-column LCD. 16 is out of range.

2. Step 2: Verify other parts

   Row 0 is valid (rows start at 0). lcd.print() can print strings. lcd.begin() is needed but not shown here, but question focuses on cursor.

3. Final Answer:

   Column index 16 is out of range for a 16-column LCD -> Option A

4. Quick Check:

   Column max index = 15 for 16 columns [OK]

Hint: Columns max at size minus one [OK]

Common Mistakes:

• Using 1-based indexing for columns
• Assuming lcd.print can't print strings
• Ignoring lcd.begin() requirement

5. You want to display a 4-letter word centered on the second row of a 20x4 LCD. Which lcd.setCursor() command correctly positions the cursor before printing?

hard

A. lcd.setCursor(8, 1);

B. lcd.setCursor(9, 1);

C. lcd.setCursor(7, 1);

D. lcd.setCursor(10, 1);

Solution

1. Step 1: Calculate center position for 4 letters on 20 columns

   Center column is 20 / 2 = 10. For 4 letters, start at 10 - (4 / 2) = 8.

2. Step 2: Set cursor to column 8 on second row

   Row 1 is second row (rows start at 0). So lcd.setCursor(8, 1) is correct.

3. Final Answer:

   lcd.setCursor(8, 1); -> Option A

4. Quick Check:

   Center start = half width minus half word length [OK]

Hint: Center = (width/2) - (word length/2) [OK]

Common Mistakes:

• Using 1-based indexing for rows or columns
• Starting cursor too far left or right
• Confusing row and column numbers