AutocadHow-ToBeginner · 4 min read

How to Send Data from Arduino to Android Using Bluetooth

To send data from Arduino to an Android device using Bluetooth, connect a Bluetooth module (like HC-05) to Arduino's serial pins and use Serial.write() or Serial.print() to send data. On Android, use a Bluetooth app or custom app to receive and display the data.

📐

Syntax

To send data via Bluetooth from Arduino, use the Serial.print() or Serial.write() functions after setting up the serial communication with the Bluetooth module.

Serial.begin(baudRate); initializes serial communication at the specified speed.
Serial.print(data); sends readable text data.
Serial.write(data); sends raw bytes.

The Bluetooth module connects to Arduino's TX and RX pins and acts as a wireless serial bridge.

arduino

void setup() {
  Serial.begin(9600); // Start serial at 9600 baud
}

void loop() {
  Serial.print("Hello Android\n"); // Send text data
  delay(1000); // Wait 1 second
}

💻

Example

This example sends the text "Hello Android" every second from Arduino to an Android device via Bluetooth. Connect an HC-05 Bluetooth module to Arduino pins 0 (RX) and 1 (TX), power it, and pair it with your Android phone. Use a Bluetooth terminal app on Android to receive the message.

arduino

void setup() {
  Serial.begin(9600); // Initialize serial communication with Bluetooth module
}

void loop() {
  Serial.println("Hello Android"); // Send data with newline
  delay(1000); // Wait 1 second
}

Output

Hello Android Hello Android Hello Android ... (repeats every second)

⚠️

Common Pitfalls

Common mistakes when sending data from Arduino to Android via Bluetooth include:

Not matching baud rates between Arduino and Bluetooth module.
Connecting Bluetooth module to wrong Arduino pins or using pins reserved for USB programming.
Forgetting to pair the Bluetooth module with the Android device before communication.
Using Serial.print() without newline when the Android app expects line breaks.

Always test with a simple Bluetooth terminal app on Android first.

arduino

/* Wrong: Using pins 0 and 1 while uploading code can cause issues */
// Avoid using pins 0 (RX) and 1 (TX) if uploading code frequently

/* Right: Use SoftwareSerial on other pins */
#include <SoftwareSerial.h>

SoftwareSerial BTSerial(10, 11); // RX, TX

void setup() {
  BTSerial.begin(9600);
}

void loop() {
  BTSerial.println("Hello Android");
  delay(1000);
}

📊

Quick Reference

Step	Description
Connect HC-05 module	Connect TX to Arduino RX, RX to Arduino TX, and power the module
Set baud rate	Use Serial.begin(9600) to match HC-05 default speed
Send data	Use Serial.print() or Serial.println() to send text
Pair device	Pair HC-05 with Android via Bluetooth settings
Receive data	Use Bluetooth terminal app on Android to read data

✅

Key Takeaways

Connect a Bluetooth module like HC-05 to Arduino serial pins and set matching baud rates.

Use Serial.print() or Serial.println() to send readable data from Arduino.

Pair the Bluetooth module with your Android device before trying to receive data.

Avoid using Arduino pins 0 and 1 for Bluetooth if you upload code often; use SoftwareSerial instead.

Test communication first with a Bluetooth terminal app on Android.