Mailbox notifier with ESP32

• Mailbox notifier with ESP32
  • Scope of Project
  • Implenmentation details
  • Quickstart Guide
  • References

Scope of Project

The aim of this project is to provide a firmware for an ESP32, using Platform.IO, to:

• Put the ESP32 in deep-sleep
• Activate the the ESP32 based on a trigger, through a mechanical switch
• Connect to WiFi
• Send an E-Mail via SMTP
• and go back to deep-sleep

The idea is that I want to be notified if the mailman puts mail into my mailbox. The goal of this project is to use cost-effective, off-the-shelve components and provide the best battery-life possible.

Implenmentation details

The ESP32 variant that was used, is called LOLIN32 Lite, that can be had for about 5 to 10 euros on Amazon.

The firmware has been developed using Platform.io and the implementation used the Arduino Framework. The exact configuration, including a list of libraries, can be found in the platformio.ini file.

The mechanical switch, that triggers a wake-up from deep sleep is configured on the GPIO 13.

The environment variables are:

Variable Name	Purpose
WIFI_SSID	The SSID (name) of the WiFi network to connect to.
WIFI_PASSWORD	The password for the WiFi network.
SMTP_HOST	The SMTP server address for sending emails.
SMTP_PORT	The port used for connecting to the SMTP server.
AUTHOR_EMAIL	The sender's email address.
AUTHOR_PASSWORD	The sender's password for the sender's email account.
RECIPIENT_EMAIL	The recipient's email address for the notification.

En example file for the .env.h can be found under src/.env.template.h.

Quickstart Guide

In order to start you need:

• Hardware
  • ESP32 with a mechanical switch connected to the RTC GPIO of your choice. Make sure that you add a 10k Ohm pull-down resistor.
  • Battery Pack, usually a single-cell LiPO battery, but this depends on the battery-management that is on your ESP32
• Credentials:
  • You have a SMTP mail server at your disposal. When you still need to create one, here is a guide on how to do that with GMail.
  • WiFi Credentials for the location that you want to test this.

If you have all of this you can follow the following steps:

• Create a copy of src/.env.template.h and rename it to src/.env.h.
• Fill in the appropiate credentials
• Build the firmware using PlatformIO
• Upload and monitor the ESP32

References

• https://randomnerdtutorials.com/esp32-send-email-smtp-server-arduino-ide/
• https://lastminuteengineers.com/esp32-deep-sleep-wakeup-sources/
• https://github.com/G6EJD/LiPo_Battery_Capacity_Estimator/blob/master/ReadBatteryCapacity_LIPO.ino