ESP32 + BME280 IoT Project

BOM

• DFRobot Firebeetle ESP32-E
• 3.7V LiPo battery
• BME280
• Rectangular rocker switch

ESP32 WiFi woes

My router does not play nice with ESP32's it seems. Using my phone's hotspot, connecting to the internet and getting a time from NTP works fine. I am getting an IP address, so I know the credentials are correct. But it seems I can't reach the internet, and get disconnected fairly quickly after connecting.
I fiddled with the security settings and changed from WPA2 + WPA3 to WPA + WPA2 and all of a sudden the ESP32 connected fine. Yay! Wanting to be thorough, I tried using WPA2 + WPA3 mode again to see if I could reproduce my issue. But no! For some weird reason it just keeps connecting now. Needs some more testing. I'll be testing a deep sleep script that sleeps for 10 minutes, then when it wakes up, gets the time and logs if it succeeded or failed to Serial. According to some sources you need to disconnect wifi before deep sleep. I have not been able to reproduce consistent failures by not disconnecting though, so I'll test without that first. Seems that I successfully got ntp time every 10 minutes. Trying with WPA2 + WPA3 for a couple of cycles. Something weird is going on with my router. I should try turning it off and on again and/or doing a hard reset.
Could it be there is some weird stateful thing going on?
Update: After tweaking WPA settings back and forth, something in the modem appears to have been nudged. I'm getting consistently connected now, and can not reproduce my issue... I have not touched anything else, I should have probably just reset my modem, before diving into the software side of things.
Update 2: WPA setting does not appear to persist properly, and it appears I have been using WPA + WPA2 this whole time... Come h4ck me!

Battery life

Experimenting with two devices with their jumper wire cut. Leaving one as is. Will turn them on at the same time. and see how long each will last.
Update I've left two devices side by side, in an attempt to minimize the WiFi interference component of the measurement. Weirdly, after 24 hours the one with its jumper cut is reporting a lower battery level than the one without the jumper cut. It's probably still just too early to say, on top of that, there are a lot of other variables that could influence the reading.

Weird readings

Sometimes I'm getting way too high or way too low pressure and humidity readings. Experimenting with initializing the BME on start up, instead of right before taking measurement.
Update This has helped, although I still sometimes get a very low pressure reading. It seems like the BME280 needs some time to initialize.

Devices

Battery powered ESP32 + BME280 modules.
They take a measurement, send it to an mqtt broker and go to sleep for TIME_TO_SLEEP, defined in ./config.h.
Arduino code can be found in ./esp32-woohoo.ino

Server

Simple rust mqtt scraper to expose prometheus metrics.
Code can be found in ./mqtt-to-prom
Grafana dashboard available in ./mqtt-to-prom/meta/grafana-dashboard.json

MQTT

If using mosquitto and running in a safe environment set

# /etc/mosquitto/mosquitto.conf
listener 1883 0.0.0.0 # Allow external connections
allow_anonymous true  # We have not set up auth

Build

esp32-woohoo.ino

• Add the FireBeetle ESP32-E board in Arduino IDE Boards Manager
  • In Arduino IDE -> File -> Preferences -> Additional Boards Manager URLs, add: http://download.dfrobot.top/FireBeetle/package_DFRobot_index.json
    • This is for the DFRobot ESP32-E version!
    • Their server is slow af, grab coffee
  • Select the board in Arduino IDE -> Tools -> Board -> DFRobot ESP32 Arduino -> DFRobot FireBeetle ESP32-E
• Ensure the following libs are installed
  • WiFi by Arduino 1.2.7
  • FastLED by Daniel Garcia 3.5.0
  • Adafruit Unified Sensor 1.15
  • Adafruit BME280 Library 2.2.2
  • https://github.com/marvinroger/async-mqtt-client
• Add a secret.h file in the root of the project with WiFi credentials

  // ./secret.h
  #define WIFI_SSID "SSID"
  #define WIFI_PASSWORD "hunter1" // lol
  

mqtt-to-prom

Make sure cross is installed

cargo install cross

If running on raspberry pi 4 with aarch64 run:

make build-pi

TODO

• Add timer to go back to sleep if connection not made
• Round values to eliminate "noise"
• [bugfix] parsing float goes wrong sometimes, write some tests
  • test this
  • output payload on parse error
  • check if happens again
• Grafana dashboard
• NTP server call
• Send out time stamps
• Blink on connection failures?
  • Needs some experimentation, might substantially reduce batter life
• Improve battery life
  • Read out SoC (on A0?)
    • Using voltage divider (10KΩ + 20KΩ)
  • Reduce/disable LED on time
  • Reduce amount of measurements taken, i.e. increase sleep time
  • Go back to deep sleep after several connection failures
  • Get better idea of battery level percentage (0-4096 but cuts out at 2000 or smth)
  • If possible light up when battery too low
• Add last will on connect()
  • Decided to skip this for now. Will do server side most likely.
• Auto config server. Loop over serial ports, check for devices and flash config to them.
  • Auto config server
  • Use EEPROM to store wifi credentials, broker location, etc.

Media

3D printed case, check ./stl for files.

Deep sleep, wake, connect wifi, connect mqtt, take measurement, send measurement, deep sleep...