Using multiple libraries together in Arduino - Step-by-Step Execution

Concept Flow - Using multiple libraries together

Start Program

↓

Include Library A

↓

Include Library B

↓

Initialize Objects from A and B

↓

Setup: Initialize both libraries

↓

Loop: Use functions from both libraries

↓

Repeat Loop

The program starts by including multiple libraries, then initializes their objects, sets them up, and uses their functions together in the main loop.

Execution Sample

Arduino

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);

void setup() {
  Wire.begin();
  lcd.init();
  lcd.backlight();
}

void loop() {
  lcd.setCursor(0,0);
  lcd.print("Hello");
}

This code uses Wire and LiquidCrystal_I2C libraries together to display 'Hello' on an LCD screen.

Execution Table

Step	Action	Library/Function	Result/State
1	Include Wire library	Wire	Wire functions available
2	Include LiquidCrystal_I2C library	LiquidCrystal_I2C	LCD functions available
3	Create lcd object	LiquidCrystal_I2C lcd	lcd ready to control LCD
4	Call Wire.begin()	Wire.begin()	I2C bus initialized
5	Call lcd.init()	lcd.init()	LCD initialized
6	Call lcd.backlight()	lcd.backlight()	LCD backlight turned on
7	Set cursor to (0,0)	lcd.setCursor(0,0)	Cursor at first row, first column
8	Print 'Hello' on LCD	lcd.print("Hello")	'Hello' displayed on LCD
9	Loop repeats	loop()	Display stays on, ready for updates

💡 Loop runs continuously; program does not exit.

Variable Tracker

Variable	Start	After setup	After loop 1	After loop 2
lcd	Not created	Created and initialized	Cursor at (0,0), 'Hello' displayed	Cursor at (0,0), 'Hello' displayed

Key Moments - 3 Insights

Why do we need to call Wire.begin() before using the LCD?

Wire.begin() initializes the I2C communication bus that the LCD uses; without it, the LCD library cannot communicate with the hardware. See execution_table step 4.

Can we use functions from both libraries in the same loop?

Yes, after initialization, you can call functions from both libraries anytime, as shown in execution_table steps 7 and 8.

What happens if we forget to call lcd.init()?

The LCD will not initialize properly and may not display anything. This is shown in execution_table step 5 where lcd.init() prepares the LCD.

Visual Quiz - 3 Questions

Look at the execution_table, what is the state after calling Wire.begin()?

A LCD backlight turned on

B I2C bus initialized

C Cursor set to (0,0)

D LCD initialized

💡 Hint

Check execution_table step 4 for Wire.begin() result.

At which step is the LCD backlight turned on?

A Step 6

B Step 5

C Step 7

D Step 8

💡 Hint

Look at execution_table for lcd.backlight() call.

If we remove Wire.begin(), what will likely happen?

A LCD will display 'Hello' normally

B Program will not compile

C LCD will not initialize or display correctly

D Backlight will turn on but no text

💡 Hint

Refer to key_moments about Wire.begin() importance.

Concept Snapshot

Using multiple libraries together:
- Include each library with #include
- Create objects for each library as needed
- Initialize each library in setup()
- Use functions from all libraries in loop()
- Ensure dependencies (like Wire.begin()) are called first

Full Transcript

This example shows how to use two Arduino libraries together: Wire and LiquidCrystal_I2C. First, both libraries are included. Then, an lcd object is created from LiquidCrystal_I2C. In setup(), Wire.begin() initializes the I2C bus, which is required for the LCD to communicate. Then lcd.init() and lcd.backlight() prepare the LCD screen. In the loop(), the cursor is set and the text 'Hello' is printed on the LCD. The loop repeats continuously, keeping the display on. Key points include calling Wire.begin() before using the LCD and initializing each library properly. This allows functions from both libraries to work together smoothly.