Receiving commands over Bluetooth in Arduino - Step-by-Step Execution

Concept Flow - Receiving commands over Bluetooth

Start Bluetooth Serial

↓

Wait for Data Available?

No→Keep Waiting

Yes↓

Read Incoming Command

↓

Process Command

↓

Execute Action

↓

Loop Back to Wait

The Arduino waits for Bluetooth data, reads commands when available, processes them, and executes actions in a loop.

Execution Sample

Arduino

void loop() {
  if (Serial.available()) {
    char cmd = Serial.read();
    if (cmd == 'A') {
      digitalWrite(LED_BUILTIN, HIGH);
    }
  }
}

This code reads a character from Bluetooth and turns on the LED if the command is 'A'.

Execution Table

Step	Serial.available()	Serial.read()	Command	Action Taken	Output
1	0 (No data)	-	-	Wait	No change
2	1 (Data available)	'A'	A	Turn LED ON	LED ON
3	1 (Data available)	'B'	B	No action	LED stays ON
4	0 (No data)	-	-	Wait	LED stays ON

💡 Loop runs continuously; waits when no data, acts when data received.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4
cmd	undefined	'A'	'B'	undefined
LED state	OFF	ON	ON	ON

Key Moments - 2 Insights

Why does the program wait when Serial.available() is 0?

Because no data has arrived yet, so the program skips reading and waits for data, as shown in step 1 and 4 of the execution_table.

What happens if the command is not 'A'?

No action is taken and the LED state remains unchanged, as seen in step 3 where command 'B' does not turn the LED on.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'cmd' at step 3?

A 'B'

B 'A'

C undefined

D 'C'

💡 Hint

Check the 'Serial.read()' and 'Command' columns at step 3 in the execution_table.

At which step does the LED turn ON according to the execution_table?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action Taken' and 'Output' columns for when LED changes state.

If Serial.available() is always 0, what will happen to the LED state?

A LED will turn ON

B LED will turn OFF

C LED state will never change

D LED will blink

💡 Hint

Refer to variable_tracker and execution_table steps where Serial.available() is 0.

Concept Snapshot

Receiving commands over Bluetooth:
- Use Serial.available() to check data
- Use Serial.read() to get command
- Use if conditions to process commands
- Execute actions like turning LED on/off
- Loop continuously to keep checking

Full Transcript

This example shows how an Arduino receives commands over Bluetooth using the Serial interface. The program continuously checks if data is available with Serial.available(). When data arrives, it reads one character with Serial.read(). If the character matches a command like 'A', it performs an action such as turning on the built-in LED. If no data is available, the program waits and checks again. This loop runs forever, allowing the Arduino to respond to Bluetooth commands anytime they come in.