Blink LED

The Blink example toggles the onboard LED state every second. It shows basic LED control using Router Bridge communication between Python® and Arduino.

Description

This example shows a simple blinking LED application. The Python® script runs a continuous loop that toggles the LED state at regular 1-second intervals. At the same time, the Arduino sketch handles the control of the LED hardware. It provides a foundation for learning basic GPIO control and Router Bridge communication patterns.

The Python® script manages the timing and state logic, while the Arduino sketch controls the LED hardware. The Router Bridge enables communication between the Python® environment and the microcontroller.

Bricks Used

This example does not use any Bricks. It shows direct Router Bridge communication between Python® and Arduino.

Hardware and Software Requirements

Hardware

• Arduino UNO Q (x1)
• USB-C® cable (for power and programming) (x1)

Software

• Arduino App Lab

Note: You can also run this example using your Arduino Arduino UNO Q as a Single Board Computer (SBC) using a USB-C® hub with a mouse, keyboard and display attached.

How to Use the Example

1. Run the App
2. Watch the LED on the board toggle state every second

How it Works

Once the application is running, the device performs the following operations:

• Managing timing and LED state in Python®.

The Python® script uses a simple loop with timing control:

    from arduino.app_utils import *
    import time
    
    led_state = False
    
    while True:
     time.sleep(1)
     led_state = not led_state
     Bridge.call("set_led_state", led_state)

The script toggles the LED state variable every second and sends the new state to the Arduino.

• Exposing LED control function to Python®.

The Arduino registers its LED control function with the Router Bridge:

    Bridge.provide("set_led_state", set_led_state);

• Controlling the hardware LED.

The Arduino sketch handles the LED hardware control:

    void set_led_state(bool state) {
        digitalWrite(LED_BUILTIN, state ? LOW : HIGH);
    }

Note that the logic is inverted (LOW for on, HIGH for off), which is typical for built-in LEDs that are wired with the cathode connected to the pin.

The high-level data flow looks like this:

Python® Timer Loop → Router Bridge → Arduino LED Control

Understanding the Code

Here is a brief explanation of the application components:

🔧 Backend (main.py)

The Python® component manages timing and LED state logic.

• import time: Provides timing functions for controlling the blink interval.

• led_state = False: Tracks the current LED state as a boolean variable.

• while True: loop : Creates an infinite loop that runs continuously to control the LED timing.

• time.sleep(1): Pauses execution for 1 second between LED state changes.

• led_state = not led_state: Toggles the LED state by inverting the boolean value.

• Bridge.call("set_led_state"): Sends the new LED state to the Arduino through the Router Bridge communication system.

🔧 Hardware (sketch.ino)

The Arduino code handles LED hardware control and sets up Bridge communication.

• pinMode(LED_BUILTIN, OUTPUT): Configures the built-in LED pin as an output for controlling the LED state.

• Bridge.begin(): Initializes the Router Bridge communication system for receiving commands from Python®.

• Bridge.provide(...): Registers the set_led_state function to be callable from the Python® script.

• set_led_state(bool state): Controls the LED hardware with inverted logic (LOW = on, HIGH = off) typical for built-in LEDs.

• Empty loop(): The main loop remains empty since all LED control is managed by the Python® script through Bridge function calls.