PicoBME690 – Indoor Climate Station

Indoor climate station built on a Raspberry Pi Pico 2 W, a Bosch BME690 sensor and a Waveshare Pico-LCD-0.96 display, written in MicroPython.

It measures temperature, humidity, air pressure and gas resistance, shows the values on the small LCD and serves a live web dashboard on your home network.

AI-assisted hobby project.

Contents

• Features
• Hardware
• Wiring
• Installation
• Controls
• Calibration
• Files
• Related project
• License

Features

• Five LCD pages: Climate, Gas / IAQ, Min / Max, Wi-Fi, System
• Screensaver with dimmed backlight after 5 minutes of inactivity
• Web dashboard with live values (updated every 5 s) and 3-hour history charts (SVG)
• JSON endpoint at /data for use in other tools, e.g. Home Assistant
• Weather trend derived from air pressure (linear regression over 3 hours)
• Relative air quality (IAQ) from gas resistance, with the baseline stored in flash and a 20-minute warm-up after boot
• Humidity corrected to the calibrated temperature (Magnus formula) plus sensor trim
• Wi-Fi with automatic reconnect, status messages and interface reset after repeated failures

Note on IAQ: The air quality value is a relative score based on the range of gas resistance the sensor has seen recently. It is not Bosch's BSEC IAQ index and does not measure specific gases or CO₂.

Hardware

Part	Details
Raspberry Pi Pico 2 W	RP2350 with Wi-Fi – datasheet
Bosch BME690 breakout	I²C, address 0x76 – product page
Waveshare Pico-LCD-0.96 (WS 19653)	0.96" LCD, 160×80, ST7735S, SPI, joystick and buttons – wiki

The hardware is relatively easy to put together; some soldering experience helps.

Wiring

The display plugs directly onto the Pico. The BME690 connects via I²C:

BME690	Pico 2 W
VCC	3V3
GND	GND
SDA	GP4
SCL	GP5

All pin assignments live in src/config.py.

Installation

1. Flash Pimoroni MicroPython for the Pico 2 W (tested with v1.29.0-2). It provides pimoroni_i2c and breakout_bme69x; these libraries are not part of this repository.

2. Copy everything from the src folder to the root of the Pico (e.g. with Thonny), no subfolders.

3. On the Pico, rename secrets_example.py to secrets.py and enter your Wi-Fi credentials:

   WIFI_SSID = "YourNetwork"
   WIFI_PASSWORD = "YourPassword"
   WIFI_COUNTRY = "DE"   # your country code

   Never upload your real secrets.py to GitHub.

4. Restart the Pico and press CTRL (joystick push) to turn on Wi-Fi. The IP address appears on the Wi-Fi page and in the REPL.

5. Open that IP address in a browser to see the dashboard.

To start Wi-Fi automatically at boot, uncomment WIFI_AUTOSTART = True in config.py. The hostname is set via WIFI_HOSTNAME in the same file.

Controls

Button	Action
A / joystick right	next page
B / joystick left	previous page
Joystick up / down	brightness
CTRL (joystick push)	Wi-Fi and web server on/off

Status codes on the System page: ONLINE, LINK? (connecting), OFFLINE, or an error: NOAP network not found, AUTH wrong password, FAIL rejected, NOIP no IP via DHCP.

Calibration

The offsets in config.py apply to one specific setup, measuring interval and an active Wi-Fi connection. Recalibrate them for your own build and location.

Setting	Current value	Meaning
TEMP_OFFSET	-3.2	added to the raw value (self-heating from Pico, Wi-Fi, display and gas heater)
HUMIDITY_TRIM	7.0	percentage points added after the Magnus correction
PRESSURE_OFFSET	1.0	hPa, compared against a DWD reference station

Findings from comparison measurements:

• Without a Wi-Fi connection the station reads about 1 °C lower, because the radio chip produces less heat.
• Direct sunlight and warm surfaces distort every measurement.
• The sensor runs on a 3-second interval; recalibrate the offset at the final location.
• Whether the humidity trim works better as a fixed amount or a factor will only become clear in dry heating-season air (35–45 %).

Files

File	Purpose
main.py	Initialisation, button handling (edge detection), main loop
config.py	Central settings: pins, intervals, calibration, IAQ, Wi-Fi
state.py	Shared state across all modules
sensors.py	Reads the BME690, applies calibration, self-test, status and trend texts
iaq.py	Relative air quality from gas resistance (shared with the Enviro+ project)
history.py	3-hour history, deltas, linear regression, uptime
display.py	LCD driver (ST7735S, 160×80) and screen pages
colors.py	Colour constants (BGR565)
web.py	HTML dashboard with SVG charts, JSON endpoint /data
wifi.py	Wi-Fi state machine with reconnect and web server polling
secrets_example.py	Template for your Wi-Fi credentials

The station creates iaq_baseline.txt on the Pico by itself; it is not part of this repository.

Related project

Pimoroni-EnviroPlus-Board – indoor environment monitor with the Pimoroni Enviro+ Pack on a Pico W, sharing the same IAQ module.

License

MIT