Bluetooth Control with HC-05

Learn how to control your robot remotely using Bluetooth and a smartphone or computer.

With Bluetooth, you can control your robot wirelessly from a phone, tablet, or PC — no need to tether it with a USB cable. In this lesson, we’ll connect an HC-05 module to the Raspberry Pi Pico and send simple commands to drive the robot.

🔌 What You’ll Need

• HC-05 Bluetooth module
• Raspberry Pi Pico
• Jumper wires
• Smartphone or computer with a serial terminal app (e.g., Bluetooth Terminal, Serial Bluetooth Terminal on Android)

⚠️ Wiring the HC-05 to the Pico

💡 The HC-05 RX pin must not receive 3.3V directly from Pico TX. Use a voltage divider (e.g., 1kΩ + 2kΩ).

🧪 Simple Bluetooth Control Script

from machine import UART, Pin, PWM
from time import sleep

# Set up Bluetooth UART
uart = UART(0, baudrate=9600, tx=Pin(0), rx=Pin(1))

# Motor pins (update to match your setup)
# ...

def forward():
    print("Forward")
    # motor code here

def backward():
    print("Backward")
    # motor code here

def left():
    print("Left")
    # motor code here

def right():
    print("Right")
    # motor code here

def stop():
    print("Stop")
    # motor stop code here

# Main loop
while True:
    if uart.any():
        cmd = uart.read(1)
        if cmd == b'f':
            forward()
        elif cmd == b'b':
            backward()
        elif cmd == b'l':
            left()
        elif cmd == b'r':
            right()
        elif cmd == b's':
            stop()

📱 Sending Commands from Your Phone

Use a Bluetooth terminal app and pair it with the HC-05 (usually pin 1234 or 0000). Then send single-character commands:

• f → forward
• b → backward
• l → left
• r → right
• s → stop

🧩 Try It Yourself

• Add more commands (e.g., speed control)
• Use a smartphone joystick app instead of typing letters
• Create a custom Bluetooth remote interface with MIT App Inventor

Now you can drive your robot like an RC car — all with MicroPython!

Next up: Wi-Fi Control with the Raspberry Pi Pico W

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