How to install the solar flare alert software on the ESP32 board

Prerequisites

Install the required tools on your computer:

pip3 install esptool adafruit-ampy pyserial

Flashing MicroPython to ESP32

The ESP32 development board is available at various places, such as Bastelgarage, where you can easily find one near you.

  • Download the recent firmware from http://micropython.org/download#esp32

  • Find your ESP32 port by running ls /dev/cu.* in the terminal

  • Erase the flash: esptool.py --chip esp32 --port /dev/cu.usbserial-0001 erase_flash

  • Flash the firmware: esptool.py --chip esp32 --port /dev/cu.usbserial-0001 --baud 460800 write_flash -z 0x1000 <DOWNLOADED_FIRMWARE>.bin

  • Open a serial terminal to check if you get a Python shell: screen /dev/cu.usbserial-0001 115200

On Mac, the port is typically /dev/cu.usbserial-0001 (M1/Apple Silicon) or /dev/cu.SLAB_USBtoUART (older Macs). If you don’t see the device, try a different USB cable (must be a data cable, not just charging).

ESP32 MicroPython tutorial

See https://docs.micropython.org/en/latest/esp32/quickref.html

Upload code

All the code for this project is on GitHub in the micropython/ directory.

The following files need to be uploaded to the ESP32:

  • wifi.dat – WiFi credentials (upload first)

  • solar_flare_alert.py – main program

  • wifi_manager.py – WiFi connection manager

  • rainbow2.py – color table for LED strip mode

  • boot.py – auto-start on boot (upload last)

Uploading with ampy

Upload all files from the Cursor terminal (boot.py last):

cd micropython
ampy --port /dev/cu.usbserial-0001 put wifi.dat
ampy --port /dev/cu.usbserial-0001 put solar_flare_alert.py
ampy --port /dev/cu.usbserial-0001 put wifi_manager.py
ampy --port /dev/cu.usbserial-0001 put rainbow2.py
ampy --port /dev/cu.usbserial-0001 put boot.py

Or as a single command:

cd micropython && ampy --port /dev/cu.usbserial-0001 put wifi.dat && ampy --port /dev/cu.usbserial-0001 put solar_flare_alert.py && ampy --port /dev/cu.usbserial-0001 put wifi_manager.py && ampy --port /dev/cu.usbserial-0001 put rainbow2.py && ampy --port /dev/cu.usbserial-0001 put boot.py

If the board is running the old program

If the old boot.py auto-starts the program, you need to stop it first:

  1. Connect via screen: screen /dev/cu.usbserial-0001 115200

  2. Press Ctrl+C (maybe several times) to get the >>> REPL prompt

  3. Wipe boot.py: f = open('boot.py', 'w'); f.write(''); f.close()

  4. Exit screen: Ctrl+A, then K, then Y

  5. Now upload files with ampy as described above

Verifying uploaded files

Connect to the REPL and check file names and sizes:

screen /dev/cu.usbserial-0001 115200

import os; [(f, os.stat(f)[6]) for f in os.listdir()]

Configuration

In solar_flare_alert.py, check if the options are correct, especially if the LED pins are correct. The pin names on ESPs are a bit weird from time to time.

The boot.py file imports solar_flare_alert and calls _main() if RUN = True. This makes the program start automatically when the board is powered.

Wiring

On our board the pins are labeled with IOxx so it is pretty straight forward. The pins deliver 3.3V and some sources say max 12mA, we use a 110 Ohm resistor.

For boards without a built-in status LED (e.g., ESP32-D), set STATUS_LED = None in solar_flare_alert.py for auto-detection, or STATUS_LED = False to disable it entirely.

Testing

In solar_flare_alert.py set RUN = False, the program loop won’t run and you can test the functions from the REPL.

Connect to the REPL via screen /dev/cu.usbserial-0001 115200, then:

import solar_flare_alert
solar_flare_alert.test_goes_to_freq_duty()  # LED brightness/blink test

For more details on the development workflow, see micropython/DEVELOPMENT.md.