Yevhen Kozachenko 🇺🇦

Posted on Oct 12 • Originally published at ekwoster.dev

🔥 MicroPython on ESP32: Build a Smart Sensor in 15 Minutes Without Writing C! 😱

#micropython #embeddedprogramming #iot #python

Based on the blog post, it focuses on building a REST API on a microcontroller (ESP32) to expose smart sensor data using MicroPython. The most fitting match among the available mdoc entries is api-development, since the core topic revolves around exposing endpoints (REST API) on a microcontroller — i.e., embedded API development — which closely aligns with general API development services.

Here is the blog post with the added highlighted message and clickable link:

🔍 Introduction

Embedded programming can often feel like trying to teach a rock to speak — daunting, opaque, and overly centered on low-level, C-heavy development. But what if you could build real-world IoT projects using the Python language you already know and love?

Welcome to the world of MicroPython, an efficient and lightweight implementation of Python 3 that runs directly on microcontrollers like the ESP32. This blog post is a deep dive into building a real-world smart sensor project in under 15 minutes using MicroPython – no Arduino IDE, no C++, and no nonsense.

TL;DR: You’ll connect a DHT11 temperature & humidity sensor to an ESP32 board, flash MicroPython, write readable Python code, and expose a REST API from the microcontroller. Yes, the ESP32 will expose an HTTP server, like a freakin’ backend for your smart home!

🧠 Why MicroPython?

Before diving into code, let's tackle the why.

Pain Points in Traditional Embedded Dev:

🔩 Low-level programming (C/C++)
🕵️‍♂️ Cryptic toolchains and cross-compiling
🔁 Slow development iterations (compile/upload/debug)

MicroPython Advantages:

🐍 Use familiar Python syntax and data structures
⚡ Instant REPL access via USB (REPL = Read Eval Print Loop)
🎯 Rapid prototyping and testing

🧰 What You’ll Need

An ESP32 development board (e.g., NodeMCU ESP32)
DHT11 or DHT22 Sensor + Jumper wires
Micro-USB cable
Thonny IDE (or any serial REPL-capable IDE)
esptool.py to flash MicroPython
MicroPython firmware for ESP32 (download here)

🔥 Hands-On: Build a Smart Weather Station

Step 1: Flash MicroPython to ESP32

pip install esptool
esptool.py --port /dev/ttyUSB0 erase_flash
esptool.py --chip esp32 --port /dev/ttyUSB0 write_flash -z 0x1000 esp32-xxxxxx.bin

Replace /dev/ttyUSB0 with your port (e.g., COM3 on Windows), and esp32-xxxxxx.bin with your firmware file.

Step 2: Connect DHT Sensor to ESP32

VCC → 3.3V
GND → GND
DATA → D4 (GPIO 4)

Step 3: Start Writing Python (On Your Microcontroller!)

Open Thonny or connect to the device via screen/REPL.

main.py

import network
import socket
import time
from machine import Pin
import dht

sensor = dht.DHT11(Pin(4))

def connect_wifi(ssid, password):
    wlan = network.WLAN(network.STA_IF)
    wlan.active(True)
    wlan.connect(ssid, password)
    while not wlan.isconnected():
        time.sleep(1)
    print('Connection successful')
    print(wlan.ifconfig())

connect_wifi('YourSSID', 'YourPassword')

addr = socket.getaddrinfo('0.0.0.0', 80)[0][-1]
s = socket.socket()
s.bind(addr)
s.listen(1)

print('Serving on', addr)

while True:
    cl, addr = s.accept()
    print('Client connected from', addr)
    sensor.measure()
    temp = sensor.temperature()
    hum = sensor.humidity()

    response = f"""
    HTTP/1.1 200 OK\r\n
    {{
        "temperature": {temp},
        "humidity": {hum}
    }}
    """
    cl.send(response)
    cl.close()

🧠 Note: You'll need to upload main.py and dht.py using Thonny or ampy. The DHT module is part of MicroPython; you may not need a separate file depending on your firmware.

Step 4: Test the Sensor

Open a browser (on the same Wi-Fi) and enter the ESP32's IP address (e.g., http://192.168.1.42). You should see a JSON response:

{
  "temperature": 26,
  "humidity": 58
}

🎉 Boom! You’ve now turned a $4 microcontroller into a REST API-powered smart sensor!

🔗 Optional: Post to a Remote Server (Webhooks)

Want to integrate with IFTTT or your own backend? Try this snippet:

import urequests

urequests.post('https://example.com/api/sensor', json={
    "temperature": temp,
    "humidity": hum
})

🚀 Real-World Use Cases

Smart home climate monitoring
Server room alerts via Telegram
Agriculture (greenhouse condition monitoring)
Wearable environmental sensors

♻️ Iteration Speed: A Game Changer

Using MicroPython, development becomes DRY (Don’t Repeat Yourself) even for firmware. Edit, save, run–no need to recompile or reflash every time.

📉 Gotchas and Limitations

MicroPython has RAM constraints (~512KB for ESP32)
Not all third-party Python libs are available
No multi-threading (but async works!)

📦 Bonus: Serve HTML UI from ESP32

Add a web interface to make the sensor public-facing:

html = """
<!DOCTYPE html>
<html>
  <head><title>Sensor</title></head>
  <body>
    <h1>Temperature: {temp} C</h1>
    <h2>Humidity: {hum}%</h2>
  </body>
</html>
"""
response = f"HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n{html.format(temp=temp, hum=hum)}"

Serve it instead of the JSON if accessed from a regular browser. Voila, your own weather dashboard!

🏁 Wrapping Up

With MicroPython and the ESP32, embedded development becomes agile, fast, and even fun. You’ve moved from zero to smart sensor REST API in under 15 minutes — no arcane build system or cryptic microcontroller C funkiness in sight.

So next time someone says "embedded dev is hard", drop this link and let them see the power of Python in the physical world. 🐍

Hit the comments below to share your setups or ask questions. If enough interest brews, we'll do BLE communication and sensor fusion in the next post!

📎 Resources

➡️ If you need this done – we offer API Development services.

DEV Community