Overview ATOM

For this assignment I worked with the M5Stack ATOM Matrix (ESP32 + 5x5 RGB LED matrix). The goal was to create a small IoT device that connects to WiFi, establishes an MQTT connection, and can be controlled remotely from a mobile application.

The device provides visual feedback using the LED matrix:

• Red face → Device powered and program started
• White vertical bar → Successful MQTT connection
• Color changes via mobile app → Remote control confirmed

Firmware Installation (UIFlow2)

Initially, the ATOM Matrix was flashed using M5Burner with the official UIFlow2 firmware for ATOM devices.

This step is required because the UIFlow2 firmware provides the M5Stack-specific MicroPython modules needed to control the LED matrix and hardware.

1. Download and install M5Burner
2. Select ATOM Matrix device
3. Choose UIFlow2 firmware
4. Flash the firmware via USB
5. Reboot and verify MicroPython environment

MicroPython Development

After flashing UIFlow2, I developed a MicroPython program that:

• Initializes the ATOM Matrix
• Displays a red face on boot
• Connects to my phone’s WiFi hotspot
• Connects to my MQTT server
• Displays a white bar once MQTT connection is successful
• Subscribes to a topic to receive color commands

The LED matrix acts as a real-time status indicator, eliminating the need for constant serial debugging.

Source Code

The complete MicroPython source code can be downloaded here:

Download MicroPython Program (main.py)

		

import os, sys, io
import M5
from M5 import *
from umqtt import MQTTClient
from hardware import RGB
from hardware import Button



mqtt_client = None
rgb = None
Btn1 = None


def mqtt_fablab_week4_blanco_event(data):
  global mqtt_client, rgb, Btn1
  rgb.set_screen([0, 0, 0, 0, 0, 0, 0xffffff, 0, 0xffffff, 0, 0, 0, 0, 0, 0, 0, 0xffffff, 0xffffff, 0xffffff, 0, 0, 0, 0, 0, 0])


def mqtt_fablab_week4_verde_event(data):
  global mqtt_client, rgb, Btn1
  rgb.set_screen([0, 0, 0, 0, 0, 0, 0x46d133, 0, 0x46d133, 0, 0, 0, 0, 0, 0, 0, 0x46d133, 0x46d133, 0x46d133, 0, 0, 0, 0, 0, 0])


def mqtt_fablab_week4_azul_event(data):
  global mqtt_client, rgb, Btn1
  rgb.set_screen([0, 0, 0, 0, 0, 0, 0x4633d1, 0, 0x4633d1, 0, 0, 0, 0, 0, 0, 0, 0x4633d1, 0x4633d1, 0x4633d1, 0, 0, 0, 0, 0, 0])


def setup():
  global mqtt_client, rgb, Btn1

  M5.begin()
  Widgets.fillScreen(0x000000)

  rgb = RGB()
  rgb.set_screen([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])
  rgb.set_brightness(20)
  rgb.set_screen([0, 0, 0, 0, 0, 0, 0xcd3232, 0, 0xcd3232, 0, 0, 0, 0, 0, 0, 0, 0xcd3232, 0xcd3232, 0xcd3232, 0, 0, 0, 0, 0, 0])
  Btn1 = Button(1, active_low=True, pullup_active=False)
  mqtt_client = MQTTClient('oscar', 'xxxxxxxx', port=1883, user='xxxxxxxx', password='xxxxxxxx', keepalive=0)
  mqtt_client.connect(clean_session=True)
  mqtt_client.subscribe('fablab/week4/blanco', mqtt_fablab_week4_blanco_event, qos=0)
  mqtt_client.subscribe('fablab/week4/verde', mqtt_fablab_week4_verde_event, qos=0)
  mqtt_client.subscribe('fablab/week4/azul', mqtt_fablab_week4_azul_event, qos=0)
  if mqtt_client.isconnected():
    rgb.set_screen([0, 0, 0xffffff, 0, 0, 0, 0, 0xffffff, 0, 0, 0, 0, 0xffffff, 0, 0, 0, 0, 0xffffff, 0, 0, 0, 0, 0xffffff, 0, 0])


def loop():
  global mqtt_client, rgb, Btn1
  M5.update()
  mqtt_client.check_msg()


if __name__ == '__main__':
  try:
    setup()
    while True:
      loop()
  except (Exception, KeyboardInterrupt) as e:
    try:
      from utility import print_error_msg
      print_error_msg(e)
    except ImportError:
      print("please update to latest firmware")

		

MQTT Communication

The ATOM Matrix connects to my MQTT broker running on a remote server. The communication flow is:

• Device connects to WiFi hotspot
• Device connects to MQTT broker (port 1883)
• Device subscribes to a command topic
• Mobile app publishes color commands
• Device updates LED face color accordingly

MIT App Inventor Mobile Application

To remotely control the device, I created a simple Android application using MIT App Inventor.

The app includes:

• Two buttons
• Each button publishes a different color command via MQTT

App Blocks

When a button is pressed, the app publishes a text message to the MQTT topic. The ATOM Matrix receives the message and updates the face color.

Results

• Boot → Red face displayed
• WiFi connection → automatic via hotspot
• MQTT connection → white bar displayed
• App control → face color changes instantly

7. Demonstration Video

Conclusions

This project demonstrates:

• Firmware flashing using M5Burner
• MicroPython development on ESP32-based hardware
• WiFi and MQTT connectivity
• Mobile IoT control via MIT App Inventor

The ATOM Matrix provides an excellent compact platform for IoT experimentation, combining visual feedback, WiFi connectivity, and simple user interaction.