Making a Heltec CubeCell-Board Plus based slan-031 environmental monitor

(Thurs 12th Feb 2026 16:03) Housing the units

The sensors and gateway now need to be housed. The following needs to be addressed:

1) Look attractive

2) Allow for display to be seen

3) Be water resistant (assume inside polytunnels will get wet)

4) Facilitate dismantling for maintenance

slan-031 and slan-093 (red tape)

A bit wet today so will return to this and search shed for materials another time.

(Weds 11th Feb 2026 20:10) Finalising the code

So over 24 hours the battery level has dropped from 4008 mV to 3980 mV. That's roughly 1 mV per hour. So will hit 3500 mV in 480 hours or 20 days - if everything keeps linear. Not bad. But what if I turned off the RGB LED after the first transmission? So here our tonight's tasks:

1) Turn off RGB LED after first transmission

2) Make code generic. That is move all secrets and ids to secret.h (don't push this to GitHub)

(21:18) Happy days. All checked in to GitHub and secrets.h.slan031 emailed to myself (this must replace the GitHub secrets.h before an operational slan-031 can be built)

Now to use this code (https://github.com/kilnageer2/HTCCAB02_LORA_DISPLAY_BME680)  to build a slan-093 by just changing secrets.h

The website: https://shannontownwetlands.ie/environmental-sensors/drumgeely-polytunnels can then be used to monitor the polytunnels (once the gateway and two devices have been boxed and deployed).

I searched in spreadsheet "2025 Attic Boxes v4" on my Google Drive to fine more Heltec HTCC-AB02 devices - though I do have one more soldered to RJ45 socket on my desk). 

Only 433 MHz ones on attic list (other attic boxes not yet added to spreadsheet!), So will have a quick look in bedroom before desoldering the one in LoRaWAN draw of my four draw cabinet by my desk. (This draw also has CubeCell Capsules x5 and Vision Master E290 x2 to get going :) )

(21:47) Found slan-031 HTCC-AB02 which successfully transmits every 5 secs but has no pins soldered to it so no sensor attached! But its orange LED charge light is on which is good,

(23:16) got slan-03 online and found great woven 4-wire cable to connect BME680 to HTCC-AB02

After battery is charged I will correct LOW_BATTERY_LEVEL and then commit tweaks to main code (added device name print statement). No need changed it to 3300 which works OK. Great. So 3.3 V low level operation limit rather than 3.5 V from normal 4.1 V.

(Tues 10th Feb 2026) Refactoring the code

This board has a long history. It is labelled slan-031 and sends readings from a BME680 sensor over LoRaWAN.

Currently, it sends temperature, humidity, battery level and atmospheric pressure every 10 minutes.

slan-031 environmental sensor

However, its charging circuit and antenna connection are broken. So no PV panel input and antenna is glued on.

I have raised Bugzilla bug #2 to track the changes needed http://192.168.1.153/bugzilla/show_bug.cgi?id=2

These being:

1) Code to be refactored into main, display, sensor and comms files.

2) Would like info displayed on reset

3) Would like info display on USER button press

4) Would like red LED to flash when battery below 3.5 V

The transmitted values can be seen by anyone at site: 

https://shannontownwetlands.ie/environmental-sensors/drumgeely-polytunnels

Website view of data

I tried the Claude Code generated files but they would compile so doing the refactoring by hand. But first to add code to GitHub

https://www.geeksforgeeks.org/git/how-to-fix-support-for-password-authentication-was-removed/

 1449  git commit -m "2nd commit, still not on GitHub"

 1450  git branch -M main

 1451  git remote add origin https://github.com/kilnageer2/HTCCAB02_LORA_DISPLAY_BME680.git

 1452  git push -u origin main

 1453  git status .

 1454  nano README.md 

 1455  git status .

 1457  git add .

 1458  git status .

 1459  git commit -m "Updated README.md"

 1460  git status .

 1461  git tag

 1462  git tag -a v1.08 -m "Initial working baseline before moving code"

 1463  git tag

 1464  git show v1.08

 1465  git status .

 1466  git push -u origin main

 1467  # Nice that remote repo is now Private!

Successfully pushed code from rhubarb laptop to GitHub using above but now need GitHub to accept it!

(17:01) Next to start messing with the code!

(18:50) Code looking good now have displays at start of device info and before first transmission of sensor data

Display after a reset of device info

Display at first transmission of sensor data

So just three things to do now:

1) Move LoRaWAN code to lorawan.cpp and lorawan.h

2) Show last sensor data and number of transmission since reset when USER button pressed

3) Flash RGB LED as red if battery below 3.5 V

(20:24) Well that's me done for the day. Tag v1.12b just has USER button code to add,

Red LED flashed and this is displayed on low battery (< 3.5 V)