Mastering the MicroPython Event Loop

MicroPython is a lean and efficient implementation of the Python 3 programming language that includes a small subset of the Python standard library and is optimized to run on microcontrollers and constrained systems. The event loop is a crucial component in MicroPython, especially when dealing with asynchronous programming. It allows you to handle multiple tasks concurrently without the need for complex threading mechanisms, which can be resource - intensive on microcontrollers. This blog will guide you through the fundamental concepts, usage methods, common practices, and best practices of the MicroPython event loop.

Table of Contents#

  1. Fundamental Concepts of MicroPython Event Loop
  2. Usage Methods
  3. Common Practices
  4. Best Practices
  5. Conclusion
  6. References

1. Fundamental Concepts of MicroPython Event Loop#

What is an Event Loop?#

An event loop is a programming construct that waits for and dispatches events or messages in a program. In the context of MicroPython, the event loop is responsible for managing asynchronous tasks. It continuously checks for events such as network requests, timer expirations, or input/output operations and schedules the appropriate tasks to handle them.

Asynchronous vs. Synchronous Programming#

  • Synchronous Programming: In synchronous programming, tasks are executed one after another. If a task takes a long time to complete, the entire program has to wait for it to finish before moving on to the next task.
  • Asynchronous Programming: Asynchronous programming allows multiple tasks to be executed concurrently. Tasks can yield control back to the event loop when they are waiting for an event, allowing other tasks to run in the meantime.

MicroPython's uasyncio Library#

MicroPython uses the uasyncio library to implement the event loop. This library provides a set of functions and classes to create and manage asynchronous tasks.

2. Usage Methods#

Installing and Importing uasyncio#

Most MicroPython firmware comes with the uasyncio library pre - installed. You can import it in your code as follows:

import uasyncio as asyncio

Creating Asynchronous Tasks#

An asynchronous task in MicroPython is defined as a coroutine. A coroutine is a special type of function that can be paused and resumed. You can define a coroutine using the async def syntax:

import uasyncio as asyncio
 
async def hello_task():
    while True:
        print("Hello, World!")
        await asyncio.sleep(1)
 
 
async def main():
    asyncio.create_task(hello_task())
    await asyncio.sleep(5)
 
 
asyncio.run(main())

In this example, the hello_task coroutine prints "Hello, World!" every second. The main coroutine creates a task from hello_task and then waits for 5 seconds.

Running the Event Loop#

The event loop can be started using the asyncio.run() function. This function takes a coroutine as an argument and runs it until it is complete.

3. Common Practices#

Handling Multiple Tasks#

You can handle multiple tasks concurrently by creating multiple coroutines and running them as tasks:

import uasyncio as asyncio
 
 
async def task1():
    while True:
        print("Task 1")
        await asyncio.sleep(1)
 
 
async def task2():
    while True:
        print("Task 2")
        await asyncio.sleep(2)
 
 
async def main():
    task_1 = asyncio.create_task(task1())
    task_2 = asyncio.create_task(task2())
    await asyncio.sleep(10)
 
 
asyncio.run(main())

In this example, task1 and task2 run concurrently, printing their respective messages at different intervals.

Handling Exceptions#

It's important to handle exceptions in asynchronous tasks. You can use a try - except block inside a coroutine to catch exceptions:

import uasyncio as asyncio
 
 
async def exception_task():
    try:
        while True:
            raise ValueError("An error occurred")
            await asyncio.sleep(1)
    except ValueError as e:
        print(f"Caught exception: {e}")
 
 
async def main():
    asyncio.create_task(exception_task())
    await asyncio.sleep(5)
 
 
asyncio.run(main())

4. Best Practices#

Resource Management#

When dealing with resources such as network connections or file descriptors, make sure to release them properly. You can use the async with statement to manage resources in an asynchronous context:

import uasyncio as asyncio
 
 
class Resource:
    def __init__(self):
        print("Resource created")
 
    def __enter__(self):
        return self
 
    def __exit__(self, exc_type, exc_val, exc_tb):
        print("Resource released")
 
 
async def resource_task():
    async with Resource() as res:
        await asyncio.sleep(2)
 
 
asyncio.run(resource_task())

Code Readability and Modularity#

Keep your code modular by separating different tasks into individual coroutines. This makes your code easier to read, test, and maintain.

Conclusion#

The MicroPython event loop, implemented through the uasyncio library, is a powerful tool for handling asynchronous programming on microcontrollers. By understanding the fundamental concepts, usage methods, common practices, and best practices, you can write efficient and robust code that can handle multiple tasks concurrently. Whether you are building a simple IoT device or a complex embedded system, the event loop can help you manage resources effectively and improve the responsiveness of your application.

References#

2025-10