Bluetooth with HC-05/HC-06 module in Arduino - Step-by-Step Execution

Concept Flow - Bluetooth with HC-05/HC-06 module

Power ON Arduino

↓

Initialize Serial

↓

Initialize Serial Bluetooth

↓

Wait for Bluetooth Connection

↓

Read Data from Bluetooth

↓

Process Data / Send Response

↓

Loop back to Read Data

The Arduino powers on, sets up serial communication with the computer and Bluetooth module, waits for Bluetooth connection, reads incoming data, processes it, and sends responses in a loop.

Execution Sample

Arduino

void setup() {
  Serial.begin(9600);
  Serial1.begin(9600); // HC-05/06
}

void loop() {
  if (Serial1.available()) {
    char c = Serial1.read();
    Serial.print(c);
  }
}

This code initializes serial communication and reads characters from the HC-05/HC-06 Bluetooth module, then prints them to the serial monitor.

Execution Table

Step	Action	Serial1.available()	Read Character	Serial Output
1	Setup: Serial and Serial1 start at 9600 baud	N/A	N/A	N/A
2	Loop start: Check if data available from Bluetooth	False	N/A	No output
3	Loop start: Data arrives from Bluetooth	True	'H'	Print 'H'
4	Loop start: Check again	True	'i'	Print 'i'
5	Loop start: Check again	False	N/A	No output
6	Loop repeats waiting for more data	N/A	N/A	N/A

💡 Loop runs continuously; stops only if Arduino is powered off or reset.

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 5	Final
c	undefined	'H'	'i'	undefined	undefined

Key Moments - 3 Insights

Why does Serial1.available() sometimes return false even if I expect data?

Serial1.available() returns true only when data has arrived and is ready to read. If no data has arrived yet, it returns false as shown in steps 2 and 5.

Why do we use Serial1 instead of Serial for the Bluetooth module?

Serial is usually connected to the USB for the computer. Serial1 is a separate hardware serial port connected to the HC-05/HC-06 module, so we use Serial1 to communicate with Bluetooth.

What happens if we don't check Serial1.available() before reading?

If we read without checking, we might get no data or garbage, causing errors. The execution table shows we only read when available is true (steps 3 and 4).

Visual Quiz - 3 Questions

Look at the execution table, what character is read at step 4?

A 'H'

B 'A'

C 'i'

D No character

💡 Hint

Check the 'Read Character' column at step 4 in the execution table.

At which step does Serial1.available() return false after reading data?

A Step 5

B Step 3

C Step 4

D Step 2

💡 Hint

Look at the 'Serial1.available()' column after data has been read in the execution table.

If we remove the Serial1.available() check, what likely happens?

A Program reads data safely

B Program may read garbage or -1

C Program stops running

D Program sends data to Bluetooth

💡 Hint

Refer to the key moment about why checking Serial1.available() is important.

Concept Snapshot

Bluetooth with HC-05/HC-06 on Arduino:
- Use Serial1 for Bluetooth communication
- Initialize with Serial1.begin(9600)
- Check Serial1.available() before reading
- Read data with Serial1.read()
- Process or forward data as needed
- Loop continuously to handle incoming data

Full Transcript

This example shows how to connect an HC-05 or HC-06 Bluetooth module to an Arduino using the Serial1 port. The Arduino starts by setting up serial communication with both the computer and the Bluetooth module. In the loop, it checks if data is available from the Bluetooth module using Serial1.available(). If data is present, it reads one character with Serial1.read() and prints it to the serial monitor. This process repeats continuously, allowing the Arduino to receive and display Bluetooth data. Checking Serial1.available() is important to avoid reading when no data is present, which could cause errors. The code runs indefinitely until the Arduino is powered off or reset.